ksh



KSH(1)                                                                  KSH(1)




NAME

       ksh,  rksh,  pfksh  - KornShell, a standard/restricted command and pro-
       gramming language


SYNOPSIS

       ksh [ abcefhikmnoprstuvxCDP ] [ -R file ] [ o option ] ... [  -  ]  [
       arg ... ]
       rksh  [  abcefhikmnoprstuvxCD ] [ -R file ] [ o option ] ...  [ - ] [
       arg ... ]


DESCRIPTION

       Ksh is a command and programming language that executes  commands  read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter ksh; it is used to set up login names and  execution  envi-
       ronments whose capabilities are more controlled than those of the stan-
       dard shell.  Rpfksh is a profile shell version of  the  command  inter-
       preter ksh; it is used to to execute commands with the attributes spec-
       ified by the user’s profiles (see pfexec(1)).  See Invocation below for
       the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

              ;   &   (   )      <   >   new-line   space   tab

       A  blank  is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or  underscore.   Identi-
       fiers  are used as components of variable names.  A vname is a sequence
       of one or more identifiers separated by a . and optionally preceded  by
       a  ..   Vnames  are  used  as function and variable names.  A word is a
       sequence of characters from the character set defined  by  the  current
       locale, excluding non-quoted metacharacters.

       A  command  is a sequence of characters in the syntax of the shell lan-
       guage.  The shell reads each command and carries out the desired action
       either  directly or by invoking separate utilities.  A built-in command
       is a command that is carried out by the shell itself without creating a
       separate  process.   Some  commands are built-in purely for convenience
       and are not documented here.  Built-ins that cause side effects in  the
       shell environment and built-ins that are found before performing a path
       search (see Execution below) are documented here.  For historical  rea-
       sons,  some  of these built-ins behave differently than other built-ins
       and are called special built-ins.

   Commands.
       A simple-command is  a  list  of  variable  assignments  (see  Variable
       Assignments  below) or a sequence of blank separated words which may be
       preceded by a list of variable  assignments  (see  Environment  below).
       The  first  word  specifies  the  name  of  the command to be executed.
       Except as specified below, the remaining words are passed as  arguments
       to  the invoked command.  The command name is passed as argument 0 (see
       exec(2)).  The value of a simple-command is its exit status;  0-255  if
       it  terminates  normally;  256+signum  if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by .  The
       standard output of each command but the last is connected by a  pipe(2)
       to the standard input of the next command.  Each command, except possi-
       bly the last, is run as a separate process; the  shell  waits  for  the
       last  command  to terminate.  The exit status of a pipeline is the exit
       status of the last command unless the pipefail option is enabled.  Each
       pipeline  can be preceded by the reserved word !  which causes the exit
       status of the pipeline to become 0 if the exit status of the last  com-
       mand is non-zero, and 1 if the exit status of the last command is 0.

       A  list  is  a sequence of one or more pipelines separated by ;, &, &,
       &&, or , and optionally terminated by ;, &, or  &.   Of  these  five
       symbols,  ;,  &, and & have equal precedence, which is lower than that
       of && and .  The symbols && and  also  have  equal  precedence.   A
       semicolon (;) causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the  preceding  pipeline
       (i.e.,  the shell does not wait for that pipeline to finish).  The sym-
       bol & causes asynchronous execution of the preceding pipeline  with  a
       two-way  pipe  established  to the parent shell; the standard input and
       output of the spawned pipeline can be written to and read from  by  the
       parent shell by applying the redirection operators <& and >& with arg p
       to commands and by using -p option of the built-in  commands  read  and
       print described later.  The symbol && () causes the list following it
       to be executed only if the preceding pipeline returns a zero (non-zero)
       value.   One  or more new-lines may appear in a list instead of a semi-
       colon, to delimit a command.

       A command is either a simple-command or one of the  following.   Unless
       otherwise  stated,  the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
              Each time a for command is executed, vname is set  to  the  next
              word  taken  from the in word list.  If in word ...  is omitted,
              then the for command executes the do list once  for  each  posi-
              tional  parameter  that  is  set  starting from 1 (see Parameter
              Expansion below).  Execution ends when there are no  more  words
              in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
              The  arithmetic  expression expr1 is evaluated first (see Arith-
              metic evaluation below).  The  arithmetic  expression  expr2  is
              repeatedly  evaluated  until  it evaluates to zero and when non-
              zero, list is executed and the arithmetic expression expr3 eval-
              uated.   If  any expression is omitted, then it behaves as if it
              evaluated to 1.

       select vname [ in word ... ] ;do list ;done
              A select command prints on standard error  (file  descriptor  2)
              the set of words, each preceded by a number.  If in word ...  is
              omitted, then the positional parameters starting from 1 are used
              instead  (see  Parameter  Expansion  below).   The PS3 prompt is
              printed and a line is read from the  standard  input.   If  this
              line consists of the number of one of the listed words, then the
              value of the variable vname is set to the word corresponding  to
              this  number.   If  this  line  is  empty, the selection list is
              printed again.  Otherwise the value of the variable vname is set
              to  null.   The contents of the line read from standard input is
              saved in the variable REPLY.  The  list  is  executed  for  each
              selection  until  a break or end-of-file is encountered.  If the
              REPLY variable is set to null by the execution of list, then the
              selection  list  is printed before displaying the PS3 prompt for
              the next selection.

       case word in [ [(]pattern [ │ pattern ] ... ) list ;; ] ... esac
              A case command executes the list associated with the first  pat-
              tern that matches word.  The form of the patterns is the same as
              that used for file-name generation  (see  File  Name  Generation
              below).   The ;; operator causes execution of case to terminate.
              If ;& is used in place of ;; the next subsequent list,  if  any,
              is executed.

       if list ;then list [ elif list ;then list ] ... [ ;else list ] ;fi
              The list following if is executed and, if it returns a zero exit
              status, the list following the first then is  executed.   Other-
              wise,  the  list following elif is executed and, if its value is
              zero, the list following the next  then  is  executed.   Failing
              each successive elif list, the else list is executed.  If the if
              list has non-zero exit status and there is no  else  list,  then
              the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
              A  while  command repeatedly executes the while list and, if the
              exit status of the last command in the list  is  zero,  executes
              the  do  list; otherwise the loop terminates.  If no commands in
              the do list are executed, then the while command returns a  zero
              exit  status;  until may be used in place of while to negate the
              loop termination test.

       ((expression))
              The expression is evaluated using the rules for arithmetic eval-
              uation  described below.  If the value of the arithmetic expres-
              sion is non-zero, the exit status is 0, otherwise the exit  sta-
              tus is 1.

       (list)
              Execute list in a separate environment.  Note, that if two adja-
              cent open parentheses are needed for nesting, a  space  must  be
              inserted  to  avoid  evaluation  as  an  arithmetic  command  as
              described above.

       { list;}
              list is simply executed.  Note that unlike the metacharacters  (
              and  ),  { and } are reserved words and must occur at the begin-
              ning of a line or after a ; in order to be recognized.

       [[ expression ]]
              Evaluates expression and returns a zero exit status when expres-
              sion is true.  See Conditional Expressions below, for a descrip-
              tion of expression.

       function varname { list ;}
       varname () { list ;}
              Define a function which is referenced by  varname.   A  function
              whose  varname contains a .  is called a discipline function and
              the portion of the varname preceding the last .  must  refer  to
              an  existing  variable.  The body of the function is the list of
              commands between { and }.  A function defined with the  function
              varname syntax can also be used as an argument to the .  special
              built-in command to get the equivalent behavior as if  the  var-
              name() syntax were used to define it.  (See Functions below.)

       time [ pipeline ]
              If  pipeline is omitted the user and system time for the current
              shell and completed  child  processes  is  printed  on  standard
              error.   Otherwise, pipeline is executed and the elapsed time as
              well as the user and system time are printed on standard  error.
              The TIMEFORMAT variable may be set to a format string that spec-
              ifies how the timing information should be displayed.  See Shell
              Variables below for a description of the TIMEFORMAT variable.

       The  following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do  done  {  }  function
       select time [[ ]] !

   Variable Assignments.
       One  or  more variable assignments can start a simple command or can be
       arguments to the typeset, export, or  readonly  special  built-in  com-
       mands.  The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
              No space is permitted between varname and the = or between = and
              word.

       varname=(assign_list)
              No space is permitted between varname and the =.  An assign_list
              can be one of the following:
                      word ...
                             Indexed array assignment.
                      [word]=word ...
                             Associative array assignment.
                      assignment ...
                             Compound  variable  assignment.   This  creates a
                             compound variable varname with  sub-variables  of
                             the  form  varname.name,  where  name is the name
                             portion of assignment.  The value of varname will
                             contain  all the assignment elements.  Additional
                             assignments made to sub-variables of varname will
                             also  be  displayed  as part of the value of var-
                             name.  If no assignments are  specified,  varname
                             will  be a compound variable allowing subsequence
                             child elements to be defined.
                      typeset [options] assignment ...
                             Nested variable assignment.  Multiple assignments
                             can  be specified by separating each of them with
                             a ;.  The previous  value  is  unset  before  the
                             assignment.

       In addition, a += can be used in place of the = to signify adding to or
       appending to the previous value.  When += is applied to  an  arithmetic
       type,  word  is  evaluated as an arithmetic expression and added to the
       current value.  When applied to a string variable, the value defined by
       word  is appended to the value.  For compound assignments, the previous
       value is not unset and the new values are appended to the current  ones
       provided that the types are compatible.

   Comments.
       A  word beginning with # causes that word and all the following charac-
       ters up to a new-line to be ignored.
   Aliasing.
       The first word of each command is replaced by the text of an  alias  if
       an alias for this word has been defined.  An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion  characters,  parameter  expansion  and  command substitution
       characters, and =.  The replacement string can contain any valid  shell
       script  including  the  metacharacters listed above.  The first word of
       each command in the replaced text, other than any that are in the  pro-
       cess  of being replaced, will be tested for aliases.  If the last char-
       acter of the alias value is a blank then the word following  the  alias
       will  also  be  checked for alias substitution.  Aliases can be used to
       redefine built-in commands but cannot be used to redefine the  reserved
       words  listed  above.  Aliases can be created and listed with the alias
       command and can be removed with the unalias command.
       Aliasing is performed when scripts are read, not while  they  are  exe-
       cuted.   Therefore,  for  an alias to take effect, the alias definition
       command has to be executed before  the  command  which  references  the
       alias is read.
       The  following  aliases are compiled into the shell but can be unset or
       redefined:
                           autoload=typeset -fu
                           command=command  
                           fc=hist
                           float=typeset -E
                           functions=typeset -f
                           hash=alias -t --
                           history=hist -l
                           integer=typeset -i
                           nameref=typeset -n
                           nohup=nohup  
                           r=hist -s
                           redirect=command exec
                           source=command .
                           stop=kill -s STOP
                           suspend=kill -s STOP $$
                           times={ { time;} 2>&1;}
                           type=whence -v

   Tilde Substitution.
       After alias substitution is performed, each word is checked to  see  if
       it begins with an unquoted .  For tilde substitution, word also refers
       to the word portion of parameter  expansion  (see  Parameter  Expansion
       below).   If  it  does, then the word up to a / is checked to see if it
       matches a user name in the password  database  (often  the  /etc/passwd
       file).   If  a  match  is  found,  the  and the matched login name are
       replaced by the login directory of the matched user.  If  no  match  is
       found, the original text is left unchanged.  A  by itself, or in front
       of a /, is replaced by $HOME.  A  followed by a + or - is replaced  by
       the value of $PWD and $OLDPWD respectively.

       In  addition,  when expanding a variable assignment, tilde substitution
       is attempted when the value of the assignment begins with a , and when
       a  appears after a :.  The : also terminates a  login name.

   Command Substitution.
       The  standard output from a command enclosed in parentheses preceded by
       a dollar sign ( $() ) or a pair of grave accents (``) may  be  used  as
       part  or  all of a word; trailing new-lines are removed.  In the second
       (obsolete) form, the string between the quotes is processed for special
       quoting  characters before the command is executed (see Quoting below).
       The command substitution $(cat file) can be replaced by the  equivalent
       but faster $(<file).

   Arithmetic Substitution.
       An  arithmetic  expression enclosed in double parentheses preceded by a
       dollar sign ( $(()) ) is  replaced  by  the  value  of  the  arithmetic
       expression within the double parentheses.

   Process Substitution.
       This feature is only available on versions of the UNIX operating system
       that support the /dev/fd directory for naming open files.  Each command
       argument  of  the  form  <(list) or >(list) will run process list asyn-
       chronously connected to some file in /dev/fd.  The name  of  this  file
       will  become  the  argument  to  the  command.   If  the form with > is
       selected then writing on this file will provide input for list.   If  <
       is used, then the file passed as an argument will contain the output of
       the list process.  For example,

              paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(pro-
              cess2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and sends it to the processes process1  and  pro-
       cess2,  as  well as putting it onto the standard output.  Note that the
       file, which is passed as an argument to the command, is a UNIX  pipe(2)
       so programs that expect to lseek(2) on the file will not work.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       , @, #, ?, -, $, and !.  A variable is denoted by a vname.  To  create
       a variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already  exist.   A  variable  has  a
       value  and  zero  or more attributes.  Variables can be assigned values
       and attributes by using the  typeset  special  built-in  command.   The
       attributes  supported by the shell are described later with the typeset
       special  built-in  command.   Exported  variables   pass   values   and
       attributes to the environment.

       The  shell supports both indexed and associative arrays.  An element of
       an array variable is referenced by a subscript.   A  subscript  for  an
       indexed  array  is  denoted by an arithmetic expression (see Arithmetic
       evaluation below) between a [ and a ].  To assign values to an  indexed
       array,  use set -A vname  value ... .  The value of all subscripts must
       be in the range  of  0  through  4095.   Indexed  arrays  need  not  be
       declared.   Any reference to a variable with a valid subscript is legal
       and an array will be created if necessary.

       An associative array is created with the -A option to typeset.  A  sub-
       script for an associative array is denoted by a string enclosed between
       [ and ].

       Referencing any array without a subscript is equivalent to  referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

              vname=value [ vname=value ] ...

       or
              vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       A  nameref  is  a  variable that is a reference to another variable.  A
       nameref is created with the -n attribute of typeset.  The value of  the
       variable  at  the time of the typeset command becomes the variable that
       will be referenced whenever the nameref variable is used.  The name  of
       a  nameref  cannot  contain a ..  When a variable or function name con-
       tains a ., and the portion of the name up to the first  .  matches  the
       name  of  a  nameref, the variable referred to is obtained by replacing
       the nameref portion with the name of the  variable  referenced  by  the
       nameref.   If a nameref is used as the index of a for loop, a name ref-
       erence is established for each item in the list.  A nameref provides  a
       convenient way to refer to the variable inside a function whose name is
       passed as an argument to a function.  For example, if  the  name  of  a
       variable is passed as the first argument to a function, the command
              typeset -n var=$1
       inside the function causes references and assignments to var to be ref-
       erences and assignments to the variable whose name has been  passed  to
       the function.
       If  either  of the floating point attributes, -E, or -F, or the integer
       attribute, -i, is set for vname, then the value is  subject  to  arith-
       metic evaluation as described below.
       Positional  parameters, parameters denoted by a number, may be assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
              The  shell reads all the characters from ${ to the matching } as
              part of the same word even if it contains braces or  metacharac-
              ters.   The value, if any, of the parameter is substituted.  The
              braces are required when parameter  is  followed  by  a  letter,
              digit,  or  underscore  that is not to be interpreted as part of
              its name, when the variable name contains a ., or when  a  vari-
              able is subscripted.  If parameter is one or more digits then it
              is a positional parameter.  A positional parameter of more  than
              one  digit  must be enclosed in braces.  If parameter is  or @,
              then all the positional parameters, starting with $1,  are  sub-
              stituted  (separated  by  a  field  separator character).  If an
              array vname with subscript  or @ is used, then  the  value  for
              each  of  the  elements  is  substituted, separated by the first
              character of the value of IFS.
       ${#parameter}
              If parameter is  or @, the number of positional  parameters  is
              substituted.   Otherwise, the length of the value of the parame-
              ter is substituted.
       ${#vname[*]}
       ${#vname[@]}
              The number of elements in the array vname is substituted.

       ${!vname}
              Expands to the name of the variable referred to by vname.   This
              will be vname except when vname is a name reference.

       ${!vname[subscript]}
              Expands  to  name  of  the subscript unless subscript is * or @.
              When subscript is *, the list of array subscripts for  vname  is
              generated.   For a variable that is not an array, the value is 0
              if the variable is set.  Otherwise it is null.   When  subscript
              is  @,  same  as  above, except that when used in double quotes,
              each array subscript yields a separate argument.

       ${!prefix*}
              Expands to the names of the variables  whose  names  begin  with
              prefix.

       ${parameter:-word}
              If  parameter  is set and is non-null then substitute its value;
              otherwise substitute word.

       ${parameter:=word}
              If parameter is not set or is null then  set  it  to  word;  the
              value  of the parameter is then substituted.  Positional parame-
              ters may not be assigned to in this way.

       ${parameter:?word}
              If parameter is set and is non-null then substitute  its  value;
              otherwise,  print  word and exit from the shell (if not interac-
              tive).  If word is omitted then a standard message is printed.

       ${parameter:+word}
              If parameter is set and is non-null then substitute word; other-
              wise substitute nothing.

       In the above, word is not evaluated unless it is to be used as the sub-
       stituted string, so that, in the following  example,  pwd  is  executed
       only if d is not set or is null:

              print ${d:-$(pwd)}

       If  the  colon  (  :  ) is omitted from the above expressions, then the
       shell only checks whether parameter is set or not.

       ${parameter:offset:length}
       ${parameter:offset}
              Expands to the portion of the value of parameter starting at the
              character (counting from 0) determined by expanding offset as an
              arithmetic expression and consisting of the number of characters
              determined  by  the arithmetic expression defined by length.  In
              the second form, the remainder of the value is used.  If A nega-
              tive  offset  counts  backwards from the end of parameter.  Note
              that one or more blanks is required in front of a minus sign  to
              prevent  the  shell  from  interpreting  the operator as :-.  If
              parameter is  or @, or is an array name indexed by  or @, then
              offset  and  length  refer to the array index and number of ele-
              ments respectively.  A negative offset is taken relative to  one
              greater  than  the  highest  subscript  for indexed arrays.  The
              order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
              If the shell pattern matches  the  beginning  of  the  value  of
              parameter,  then the value of this expansion is the value of the
              parameter with the matched portion deleted; otherwise the  value
              of  this parameter is substituted.  In the first form the small-
              est matching pattern is deleted  and  in  the  second  form  the
              largest matching pattern is deleted.  When parameter is @, *, or
              an array variable with subscript @ or *, the substring operation
              is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
              If  the shell pattern matches the end of the value of parameter,
              then the value of this expansion is the value of  the  parameter
              with the matched part deleted; otherwise substitute the value of
              parameter.  In the first form the smallest matching  pattern  is
              deleted  and  in the second form the largest matching pattern is
              deleted.  When parameter is @, *, or an array variable with sub-
              script  @  or *, the substring operation is applied to each ele-
              ment in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
              Expands parameter and replaces the longest match of pattern with
              the  given  string.  Each occurrence of \n in string is replaced
              by the portion of parameter that matches the  n-th  sub-pattern.
              In  the  first  form,  only  the  first occurrence of pattern is
              replaced.  In  the  second  form,  each  match  for  pattern  is
              replaced by the given string.  The third form restricts the pat-
              tern match to the beginning of the string while the fourth  form
              restricts  the  pattern  match  to  the end of the string.  When
              string is null, the pattern will be deleted and the /  in  front
              of  string  may be omitted.  When parameter is @, *, or an array
              variable with subscript @ or *, the  substitution  operation  is
              applied  to each element in turn.  In this case, the string por-
              tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
              #      The number of positional parameters in decimal.
              -      Options supplied to the shell on invocation or by the set
                     command.
              ?      The  decimal value returned by the last executed command.
              $      The process number of this shell.
              _      Initially, the value of _ is an absolute pathname of  the
                     shell  or script being executed as passed in the environ-
                     ment.  Subsequently it is assigned the last  argument  of
                     the previous command.  This parameter is not set for com-
                     mands which are asynchronous.   This  parameter  is  also
                     used  to  hold  the  name  of the matching MAIL file when
                     checking for mail.
              !      The  process  number  of  the  last  background   command
                     invoked.
              .sh.command
                     When  processing a DEBUG trap, this variable contains the
                     current command line that is about to run.
              .sh.edchar
                     This variable contains the value of the keyboard  charac-
                     ter  (or sequence of characters if the first character is
                     an ESC, ascii 033) that has been entered when  processing
                     a  KEYBD  trap (see Key Bindings below).  If the value is
                     changed as part of the trap action, then  the  new  value
                     replaces  the key (or key sequence) that caused the trap.
              .sh.edcol
                     The character position of the cursor at the time  of  the
                     most recent KEYBD trap.
              .sh.edmode
                     The  value  is  set  to  ESC when processing a KEYBD trap
                     while in vi insert mode.  (See Vi Editing Mode    below.)
                     Otherwise,  .sh.edmode  is  null  when processing a KEYBD
                     trap.
              .sh.edtext
                     The characters in the input buffer at  the  time  of  the
                     most  recent KEYBD trap.  The value is null when not pro-
                     cessing a KEYBD trap.
              .sh.file
                     The pathname of the file than contains the  current  com-
                     mand.
              .sh.fun
                     The  name of the current function that is being executed.
              .sh.match
                     An indexed array which stores the most recent  match  and
                     sub-pattern  matches after variables expansions using the
                     operators #, %, or /.  The 0-th element stores  the  com-
                     plete  match  and the i-th.  element stores the i-th sub-
                     match.  The .sh.match variable  becomes  unset  when  the
                     variable that has expanded is assigned a new value.
              .sh.name
                     Set to the name of the variable at the time that a disci-
                     pline function is invoked.
              .sh.subscript
                     Set to the name subscript of the  variable  at  the  time
                     that a discipline function is invoked.
              .sh.subshell
                     The current depth for subshells and command substitution.
              .sh.value
                     Set to the value of the variable at the time that the set
                     or append discipline function is invoked.
              .sh.version
                     Set to a value that identifies the version of this shell.
              LINENO The current line number within  the  script  or  function
                     being executed.
              OLDPWD The previous working directory set by the cd command.
              OPTARG The  value  of  the last option argument processed by the
                     getopts built-in command.
              OPTIND The index of the last option argument  processed  by  the
                     getopts built-in command.
              PPID   The process number of the parent of the shell.
              PWD    The present working directory set by the cd command.
              RANDOM Each  time this variable is referenced, a random integer,
                     uniformly distributed between 0 and 32767, is  generated.
                     The  sequence  of  random  numbers  can be initialized by
                     assigning a numeric value to RANDOM.
              REPLY  This variable is set by the select statement and  by  the
                     read built-in command when no arguments are supplied.
              SECONDS
                     Each time this variable is referenced, the number of sec-
                     onds since shell invocation is returned.  If  this  vari-
                     able  is  assigned  a value, then the value returned upon
                     reference will be the value that was  assigned  plus  the
                     number of seconds since the assignment.

       The following variables are used by the shell:
              CDPATH The search path for the cd command.
              COLUMNS
                     If  this variable is set, the value is used to define the
                     width of the edit window for the shell edit modes and for
                     printing select lists.
              EDITOR If the value of this variable ends in emacs, gmacs, or vi
                     and the VISUAL variable is not set, then the  correspond-
                     ing option (see Special Command set below) will be turned
                     on.
              ENV    If this variable is set, then parameter  expansion,  com-
                     mand  substitution,  and arithmetic substitution are per-
                     formed on the value  to  generate  the  pathname  of  the
                     script  that  will  be executed when the shell is invoked
                     (see Invocation below).  This file is typically used  for
                     alias  and  function  definitions.   The default value is
                     $HOME/.kshrc.
              FCEDIT Obsolete name for the default editor name  for  the  hist
                     command.  FCEDIT is not used when HISTEDIT is set.
              FIGNORE
                     A  pattern that defines the set of filenames that will be
                     ignored when performing filename matching.
              FPATH  The search path for function definitions.   The  directo-
                     ries  in  this path are searched for a file with the same
                     name as the function or command when a function with  the
                     -u  attribute  is  referenced  and  when a command is not
                     found.  If an executable file with the name of that  com-
                     mand  is  found, then it is read and executed in the cur-
                     rent environment.  Unlike  PATH,  the  current  directory
                     must be represented explictily by .  rather than by adja-
                     cent : characters or a beginning or ending :.
              HISTCMD
                     Number of the current command in the history file.
              HISTEDIT
                     Name for the default editor name for the hist command.
              HISTFILE
                     If this variable is set when the shell is  invoked,  then
                     the  value  is the pathname of the file that will be used
                     to  store  the  command  history  (see  Command  Re-entry
                     below).
              HISTSIZE
                     If  this  variable is set when the shell is invoked, then
                     the  number  of  previously  entered  commands  that  are
                     accessible by this shell will be greater than or equal to
                     this number.  The default is 128.
              HOME   The default argument (home directory) for the cd command.
              IFS    Internal  field separators, normally space, tab, and new-
                     line that are used to separate  the  results  of  command
                     substitution  or  parameter  expansion  and  to  separate
                     fields with the built-in command read.  The first charac-
                     ter of the IFS variable is used to separate arguments for
                     the "$" substitution (see Quoting below).   Each  single
                     occurrence of an IFS character in the string to be split,
                     that is not in the isspace character class, and any adja-
                     cent  characters in IFS that are in the isspace character
                     class, delimit a field.  One or more  characters  in  IFS
                     that  belong  to  the  isspace character class, delimit a
                     field.   In  addition,  if  the  same  isspace  character
                     appears  consecutively  inside  IFS,  this  character  is
                     treated as if it were not in the isspace class,  so  that
                     if  IFS consists of two tab characters, then two adjacent
                     tab characters delimit a null field.
              LANG   This variable determines the locale category for any cat-
                     egory  not specifically selected with a variable starting
                     with LC_ or LANG.
              LC_ALL This variable overrides the value of  the  LANG  variable
                     and any other LC_ variable.
              LC_COLLATE
                     This  variable determines the locale category for charac-
                     ter collation information.
              LC_CTYPE
                     This variable determines the locale category for  charac-
                     ter  handling  functions.   It  determines  the character
                     classes for pattern matching (see  File  Name  Generation
                     below).
              LC_NUMERIC
                     This variable determines the locale category for the dec-
                     imal point character.
              LINES  If this variable is set, the value is used  to  determine
                     the  column  length  for  printing  select lists.  Select
                     lists will print vertically  until  about  two-thirds  of
                     LINES lines are filled.
              MAIL   If  this  variable  is set to the name of a mail file and
                     the MAILPATH variable is not set, then the shell  informs
                     the user of arrival of mail in the specified file.
              MAILCHECK
                     This  variable specifies how often (in seconds) the shell
                     will check for changes in the modification time of any of
                     the  files  specified  by the MAILPATH or MAIL variables.
                     The default value is 600  seconds.   When  the  time  has
                     elapsed  the  shell  will  check  before issuing the next
                     prompt.
              MAILPATH
                     A colon ( : ) separated list  of  file  names.   If  this
                     variable  is  set, then the shell informs the user of any
                     modifications to the specified files that  have  occurred
                     within the last MAILCHECK seconds.  Each file name can be
                     followed by a ?  and a message that will be printed.  The
                     message will undergo parameter expansion, command substi-
                     tution, and arithmetic substitution with the variable  $_
                     defined  as  the  name of the file that has changed.  The
                     default message is you have mail in $_.
              PATH   The search path for commands (see Execution below).   The
                     user  may not change PATH if executing under rksh (except
                     in .profile).
              PS1    The value of this  variable  is  expanded  for  parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion to define the primary prompt string which by default
                     is  ‘‘$’’.  The character !  in the primary prompt string
                     is replaced by the command number (see  Command  Re-entry
                     below).   Two successive occurrences of !  will produce a
                     single !  when the prompt string is printed.
              PS2    Secondary prompt string, by default ‘‘> ’’.
              PS3    Selection prompt string used within  a  select  loop,  by
                     default ‘‘#? ’’.
              PS4    The  value  of  this  variable  is expanded for parameter
                     evaluation, command substitution, and arithmetic  substi-
                     tution  and precedes each line of an execution trace.  By
                     default, PS4 is ‘‘+ ’’.  In addition when PS4  is  unset,
                     the execution trace prompt is also ‘‘+ ’’.
              SHELL  The pathname of the shell is kept in the environment.  At
                     invocation, if the basename  of  this  variable  is  rsh,
                     rksh,  or krsh, then the shell becomes restricted.  If it
                     is pfsh or pfksh, then the shell becomes a profile  shell
                     (see pfexec(1)).
              TIMEFORMAT
                     The  value  of  this parameter is used as a format string
                     specifying how the timing information for pipelines  pre-
                     fixed  with  the  time reserved word should be displayed.
                     The % character introduces  a  format  sequence  that  is
                     expanded  to a time value or other information.  The for-
                     mat sequences and their meanings are as follows.
                     %%        A literal %.
                     %[p][l]R  The elapsed time in seconds.
                     %[p][l]U  The number of CPU seconds spent in user mode.
                     %[p][l]S  The number of CPU seconds spent in system mode.
                     %P        The CPU percentage, computed as (U + S) / R.

                     The braces denote optional portions.  The optional p is a
                     digit specifying the precision, the number of  fractional
                     digits  after  a  decimal  point.  A value of 0 causes no
                     decimal point or fraction to be output.   At  most  three
                     places  after  the decimal point can be displayed; values
                     of p greater than 3 are treated as 3.  If p is not speci-
                     fied, the value 3 is used.

                     The optional l specifies a longer format, including hours
                     if greater than zero, minutes, and seconds  of  the  form
                     HHhMMmSS.FFs.   The  value of p determines whether or not
                     the fraction is included.

                     All other characters are  output  without  change  and  a
                     trailing  newline is added.  If unset, the default value,
                     $\nreal\t%2lR\nuser\t%2lU\nsys%2lS, is  used.   If  the
                     value is null, no timing information is displayed.

              TMOUT  If  set  to  a value greater than zero, TMOUT will be the
                     default timeout value for the read built-in command.  The
                     select  compound  command  terminates after TMOUT seconds
                     when input is from a terminal.  Otherwise, the shell will
                     terminate  if a line is not entered within the prescribed
                     number of seconds while reading from a  terminal.   (Note
                     that  the  shell can be compiled with a maximum bound for
                     this value which cannot be exceeded.)

              VISUAL If the value of this variable ends in emacs, gmacs, or vi
                     then  the  corresponding  option (see Special Command set
                     below) will be turned on.  The value of VISUAL  overrides
                     the value of EDITOR.

       The  shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set  at
       all  by  the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of sub-
       stitutions  are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit  null  fields  (""  or ) are retained.  Implicit null fields
       (those resulting from parameters that have no values or command substi-
       tutions with no output) are removed.

   File Name Generation.
       Following  splitting, each field is scanned for the characters , ?, (,
       and [ unless the -f option has been set.  If one  of  these  characters
       appears, then the word is regarded as a pattern.  Each file name compo-
       nent that contains any pattern character is  replaced  with  a  lexico-
       graphically  sorted  set  of  names  that matches the pattern from that
       directory.  If no file name is found that  matches  the  pattern,  then
       that  component  of the filename is left unchanged.  If FIGNORE is set,
       then each file name component that matches the pattern defined  by  the
       value  of  FIGNORE  is  ignored when generating the matching filenames.
       The names .  and ..  are also ignored.  If  FIGNORE  is  not  set,  the
       character  .   at the start of each file name component will be ignored
       unless the first character of the pattern corresponding to this  compo-
       nent  is the character .  itself.  Note, that for other uses of pattern
       matching the / and .  are not treated specially.

                    Matches any string, including the null string.  When used
                     for filename expansion, if the globstar option is on, two
                     adjacent ’s by itself will match all files and  zero  or
                     more  directories and subdirectories.  If followed by a /
                     than only directories and subdirectories will match.
              ?      Matches any single character.
              [...]  Matches any one of the enclosed characters.   A  pair  of
                     characters separated by - matches any character lexically
                     between the pair, inclusive.  If the first character fol-
                     lowing  the  opening  [  is  a  !  then any character not
                     enclosed is matched.  A - can be included in the  charac-
                     ter set by putting it as the first or last character.
                     Within  [  and ], character classes can be specified with
                     the syntax [:class:] where class is one of the  following
                     classes  defined  in the ANSI-C standard: (Note that word
                     is equivalent to alnum plus the character _).
              alnum alpha blank cntrl digit  graph  lower  print  punct  space
              upper word xdigit
              Within  [  and ], an equivalence class can be specified with the
              syntax [=c=] which matches all characters with the same  primary
              collation weight (as defined by the current locale) as the char-
              acter c.
              Within [ and ], [.symbol.]  matches the collating symbol symbol.
       A  pattern-list  is  a list of one or more patterns separated from each
       other with a & or .  A & signifies that all patterns must  be  matched
       whereas    requires  that only one pattern be matched.  Composite pat-
       terns can be formed with one or more of the following sub-patterns:
              ?(pattern-list)
                     Optionally matches any one of the given patterns.
              *(pattern-list)
                     Matches zero or more occurrences of the given patterns.
              +(pattern-list)
                     Matches one or more occurrences of the given patterns.
              {n}(pattern-list)
                     Matches n occurrences of the given patterns.
              {m,n}(pattern-list)
                     Matches from m to n occurrences of  the  given  patterns.
                     If  m  is  omitted,  0  will be used.  If n is omitted at
                     least m occurrences will be matched.
              @(pattern-list)
                     Matches exactly one of the given patterns.
              !(pattern-list)
                     Matches anything except one of the given patterns.
       By default, each pattern, or sub-pattern will match the longest  string
       possible consistent with generating the longest overall match.  If more
       than one match is possible, the one starting closest to  the  beginning
       of the string will be chosen.   However, for each of the above compound
       patterns a - can be inserted in front of the ( to  cause  the  shortest
       match to the specified pattern-list to be used.

       When  pattern-list is contained within parenthesis, the backslash char-
       acter \ is treated specially even when inside a character class.    All
       ANSI-C character escapes are recognized and match the specified charac-
       ter.  In addition the following escape sequences are recognized:
              \d     Matches any charcter in the digit class.
              \D     Matches any charcter not in the digit class.
              \s     Matches any charcter in the space class.
              \S     Matches any charcter not in the space class.
              \w     Matches any charcter in the word class.
              \W     Matches any charcter not in the word class.

       Each sub-pattern in a composite pattern is numbered, starting at 1,  by
       the  location of the ( within the pattern.  The sequence \n, where n is
       a single digit and \n comes after the n-th.  sub-pattern,  matches  the
       same string as the sub-pattern itself.

       Finally  a  pattern can contain sub-patterns of the form (options:pat-
       tern-list).  where either options  or  :pattern-list  can  be  omitted.
       Unlike, the other compound patterns, these sub-patterns are not counted
       in the numbered sub-patterns.  If options is present, it can consist of
       one or more of the following:
              +      Enable the following options.  This is the default.
              -      Disable the following options.
              i      Treat the match as case insensitive.
              g      File the longest match (greedy).  This is the default.
       If both options and :pattern-list are specified, then the options apply
       only to  pattern-list.  Otherwise, these options remain in effect until
       they  are  disabled by a subseqent (...) or at the end of the sub-pat-
       tern containing (...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special  meaning  to  the shell and causes termination of a word unless
       quoted.  A character may be quoted (i.e., made to stand for itself)  by
       preceding  it with a \.  The pair \new-line is removed.  All characters
       enclosed between a pair of single quote marks () that is not preceded
       by  a  $  are  quoted.   A single quote cannot appear within the single
       quotes.  A single quoted string preceded by an unquoted $ is  processed
       as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
              Expands to the collating element name.

       Inside  double  quote  marks  (""),  parameter and command substitution
       occur and \ quotes the characters \, `, ", and $.  A $ in  front  of  a
       double  quoted string will be ignored in the "C" or "POSIX" locale, and
       may cause the string to be replaced by a locale specific string  other-
       wise.   The  meaning  of $ and $@ is identical when not quoted or when
       used as a variable assignment value or as a file name.   However,  when
       used  as a command argument, "$" is equivalent to "$1d$2d...", where d
       is the first character of the IFS variable, whereas "$@" is  equivalent
       to  "$1" "$2" ....  Inside grave quote marks (``), \ quotes the charac-
       ters \, `, and $.  If the grave quotes occur within double quotes, then
       \ also quotes the character ".

       The  special  meaning  of  reserved  words or aliases can be removed by
       quoting any character of the reserved word.  The recognition  of  func-
       tion  names or built-in command names listed below cannot be altered by
       quoting them.

   Arithmetic Evaluation.
       The shell performs arithmetic evaluation for  arithmetic  substitution,
       to  evaluate  an  arithmetic command, to evaluate an indexed array sub-
       script, and to evaluate arguments to the built-in  commands  shift  and
       let.   Evaluations  are performed using double precision floating point
       arithmetic or long double precision floating  point  for  systems  that
       provide  this  data  type.   Floating point constants follow the ANSI-C
       programming language floating  point  conventions.   Integer  constants
       follow  the  ANSI-C  programming  language integer constant conventions
       although only single byte character constants are recognized and  char-
       acter  casts  are  not recognized.  In addition constants can be of the
       form [base#]n where base is a decimal number between two and sixty-four
       representing  the  arithmetic base and n is a number in that base.  The
       digits above 9 are represented by the lower  case  letters,  the  upper
       case  letters,  @, and _ respectively.  For bases less than or equal to
       36, upper and lower case characters can be used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associa-
       tivity  of  expression as the C language.  All the C language operators
       that apply to floating point quantities can be used.  In addition,  the
       operator  **  can be used for exponentiation.  It has higher precedence
       than multiplication as is left  associative.   In  addition,  when  the
       value of an arithmetic variable or sub-expression can be represented as
       a long integer, all C language integer  arithmetic  operations  can  be
       performed.   Variables  can  be referenced by name within an arithmetic
       expression without using the parameter expansion syntax.  When a  vari-
       able is referenced, its value is evaluated as an arithmetic expression.

       The following math library functions can be  used  with  an  arithmetic
       expression:

       abs  acos asin atan atan2 cos cosh exp floor fmod hypot int log pow sin
       sinh sqrt tan tanh

       An internal representation of a variable as a double precision floating
       point  can be specified with the -E [n] or -F [n] option of the typeset
       special built-in command.  The -E option causes the  expansion  of  the
       value  to be represented using scientific notation when it is expanded.
       The optional option argument n defines the number of  significant  fig-
       ures.  The -F option causes the expansion to be represented as a float-
       ing decimal number when it is expanded.  The optional option argument n
       defines the number of places after the decimal point in this case.

       An  internal integer representation of a variable can be specified with
       the -i [n]  option  of  the  typeset  special  built-in  command.   The
       optional option argument n specifies an arithmetic base to be used when
       expanding the variable.  If you do not specify an arithmetic base, base
       10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable with the -E, -F, or -i attribute.  Assigning a floating  point
       number  to  a  variable  whose type is an integer causes the fractional
       part to be truncated.


   Prompting.
       When used interactively, the shell prompts with the value of PS1  after
       expanding  it for parameter expansion, command substitution, and arith-
       metic substitution, before reading a command.  In addition, each single
       !   in the prompt is replaced by the command number.  A !!  is required
       to place !  in the prompt.  If at any time a new-line is typed and fur-
       ther  input  is needed to complete a command, then the secondary prompt
       (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A conditional expression is used with the [[ compound command  to  test
       attributes  of  files and to compare strings.  Field splitting and file
       name generation are not performed on the words between [[ and ]].  Each
       expression  can  be constructed from one or more of the following unary
       or binary expressions:
       string True, if string is not null.
       -a file
              Same as -e below.  This is obsolete.
       -b file
              True, if file exists and is a block special file.
       -c file
              True, if file exists and is a character special file.
       -d file
              True, if file exists and is a directory.
       -e file
              True, if file exists.
       -f file
              True, if file exists and is an ordinary file.
       -g file
              True, if file exists and it has its setgid bit set.
       -k file
              True, if file exists and it has its sticky bit set.
       -n string
              True, if length of string is non-zero.
       -o option
              True, if option named option is on.
       -p file
              True, if file exists and is a fifo special file or a pipe.
       -r file
              True, if file exists and is readable by current process.
       -s file
              True, if file exists and has size greater than zero.
       -t fildes
              True, if file descriptor number fildes is  open  and  associated
              with a terminal device.
       -u file
              True, if file exists and it has its setuid bit set.
       -w file
              True, if file exists and is writable by current process.
       -x file
              True,  if  file exists and is executable by current process.  If
              file exists and is a directory, then true if the current process
              has permission to search in the directory.
       -z string
              True, if length of string is zero.
       -L file
              True, if file exists and is a symbolic link.
       -h file
              True, if file exists and is a symbolic link.
       -N file
              True,  if  file exists and the modification time is greater than
              the last access time.
       -O file
              True, if file exists and is owned by the effective  user  id  of
              this process.
       -G file
              True,  if  file exists and its group matches the effective group
              id of this process.
       -S file
              True, if file exists and is a socket.
       file1 -nt file2
              True, if file1 exists and file2 does not, or file1 is newer than
              file2.
       file1 -ot file2
              True, if file2 exists and file1 does not, or file1 is older than
              file2.
       file1 -ef file2
              True, if file1 and file2 exist and refer to the same file.
       string == pattern
              True, if string matches pattern.  Any part  of  pattern  can  be
              quoted to cause it to be matched as a string.
       string = pattern
              Same as == above, but is obsolete.
       string != pattern
              True, if string does not match pattern.
       string1 < string2
              True,  if  string1  comes before string2 based on ASCII value of
              their characters.
       string1 > string2
              True, if string1 comes after string2 based  on  ASCII  value  of
              their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
              True, if exp1 is equal to exp2.
       exp1 -ne exp2
              True, if exp1 is not equal to exp2.
       exp1 -lt exp2
              True, if exp1 is less than exp2.
       exp1 -gt exp2
              True, if exp1 is greater than exp2.
       exp1 -le exp2
              True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
              True, if exp1 is greater than or equal to exp2.

       In  each  of  the  above expressions, if file is of the form /dev/fd/n,
       where n is an integer, then the test is applied to the open file  whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
              True, if expression is true.  Used to group expressions.
       ! expression
              True if expression is false.
       expression1 && expression2
              True, if expression1 and expression2 are both true.
       expression1  expression2
              True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output  may  be  redirected
       using  a  special notation interpreted by the shell.  The following may
       appear anywhere in a simple-command or may precede or follow a  command
       and  are  not  passed on to the invoked command.  Command substitution,
       parameter expansion, and arithmetic substitution occur before  word  or
       digit  is used except as noted below.  File name generation occurs only
       if the shell is interactive and the  pattern  matches  a  single  file.
       Field splitting is not performed.

       In  each  of  the  following  redirections,  if  file  is  of  the form
       /dev/tcp/host/port, or /dev/udp/host/port, where host is a hostname  or
       host  address,  and  port is a service given by name or an integer port
       number, then the redirection attempts to make a tcp or  udp  connection
       to the corresponding socket.

       <word         Use file word as standard input (file descriptor 0).

       >word         Use file word as standard output (file descriptor 1).  If
                     the file does not exist then it is created.  If the  file
                     exists,  and  the  noclobber option is on, this causes an
                     error; otherwise, it is truncated to zero length.

       >|word        Sames as  >,  except  that  it  overrides  the  noclobber
                     option.

       >>word        Use  file  word  as standard output.  If the file exists,
                     then output is appended to it (by first  seeking  to  the
                     end-of-file); otherwise, the file is created.

       <>word        Open file word for reading and writing as standard input.

       <<[-]word     The shell input is read up to a line that is the same  as
                     word after any quoting has been removed, or to an end-of-
                     file.  No parameter substitution,  command  substitution,
                     arithmetic  substitution  or file name generation is per-
                     formed on word.  The resulting document, called  a  here-
                     document,  becomes  the standard input.  If any character
                     of word is quoted, then no interpretation is placed  upon
                     the  characters  of  the  document;  otherwise, parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion  occur,  \new-line is ignored, and \ must be used to
                     quote the characters \, $, `.  If - is  appended  to  <<,
                     then all leading tabs are stripped from word and from the
                     document.

       <<<word       A short form of here document in which word  becomes  the
                     contents   of   the  here-document  after  any  parameter
                     expansion, command substitution, and arithmetic substitu-
                     tion occur.

       <&digit       The  standard  input  is  duplicated from file descriptor
                     digit (see dup(2)).  Similarly for  the  standard  output
                     using >&digit.

       <&digit-      The  file  descriptor given by digit is moved to standard
                     input.  Similarly for the standard output using >&digit-.

       <&-           The standard input is closed.  Similarly for the standard
                     output using >&-.

       <&p           The input from the co-process is moved to standard input.

       >&p           The output to the co-process is moved to standard output.

       If one of the above is preceded by a digit, then  the  file  descriptor
       number  referred  to  is  that  specified  by the digit (instead of the
       default 0 or 1).  For example:

              ... 2>&1

       means file descriptor 2 is to be opened for writing as a  duplicate  of
       file descriptor 1.

       The  order  in  which  redirections  are specified is significant.  The
       shell evaluates each redirection in  terms  of  the  (file  descriptor,
       file) association at the time of evaluation.  For example:

              ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).   If the order of redirections were reversed, file descriptor 2
       would be associated with the terminal (assuming file descriptor  1  had
       been) and then file descriptor 1 would be associated with file fname.

       If  a  command is followed by & and job control is not active, then the
       default standard input for the command is  the  empty  file  /dev/null.
       Otherwise,  the environment for the execution of a command contains the
       file descriptors of the invoking  shell  as  modified  by  input/output
       specifications.

   Environment.
       The  environment (see environ(7)) is a list of name-value pairs that is
       passed to an executed program in the same  way  as  a  normal  argument
       list.   The  names  must  be  identifiers  and the values are character
       strings.  The shell interacts with the environment in several ways.  On
       invocation,  the shell scans the environment and creates a variable for
       each name found, giving it the corresponding value and  attributes  and
       marking  it export.  Executed commands inherit the environment.  If the
       user modifies the values of these variables or creates new ones,  using
       the export or typeset -x commands, they become part of the environment.
       The environment seen by any executed command is thus  composed  of  any
       name-value pairs originally inherited by the shell, whose values may be
       modified by the current shell, plus any additions which must  be  noted
       in export or typeset -x commands.

       The  environment for any simple-command or function may be augmented by
       prefixing it with one or more variable assignments.  A variable assign-
       ment argument is a word of the form identifier=value.  Thus:

              TERM=450 cmd args                  and
              (export TERM; TERM=450; cmd args)

       are  equivalent  (as  far  as  the  above execution of cmd is concerned
       except for special built-in commands listed below - those that are pre-
       ceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed in the environment, even if they occur after the  command  name.
       The following first prints a=b c and then c:

              echo a=b c
              set -k
              echo a=b c
       This  feature  is  intended for use with scripts written for early ver-
       sions of the shell and its use in new scripts is strongly  discouraged.
       It is likely to disappear someday.

   Functions.
       For  historical  reasons,  there  are two ways to define functions, the
       name() syntax and the function name syntax, described in  the  Commands
       section  above.   Shell  functions  are  read in and stored internally.
       Alias names are resolved when the function is read.  Functions are exe-
       cuted like commands with the arguments passed as positional parameters.
       (See Execution below.)

       Functions defined by the function name syntax and called by  name  exe-
       cute  in the same process as the caller and share all files and present
       working directory with the caller.  Traps  caught  by  the  caller  are
       reset  to  their  default action inside the function.  A trap condition
       that is not caught or ignored by the function causes  the  function  to
       terminate  and  the condition to be passed on to the caller.  A trap on
       EXIT set inside a function is executed in the environment of the caller
       after the function completes.  Ordinarily, variables are shared between
       the calling program and the function.   However,  the  typeset  special
       built-in  command  used within a function defines local variables whose
       scope includes the current function.  They can be passed  to  functions
       that they call in the variable assignment list the precedes the call or
       as arguments passed as name references.  Errors within functions return
       control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function name syntax that are invoked with the .  special built-in  are
       executed  in the caller’s environment and share all variables and traps
       with the caller.  Errors within these  function  executions  cause  the
       script that contains them to abort.

       The  special  built-in  command  return is used to return from function
       calls.

       Function names can be listed with the -f or +f option  of  the  typeset
       special  built-in command.  The text of functions, when available, will
       also be listed with -f.  Functions can be undefined with the -f  option
       of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions that need to be defined across separate  invocations  of  the
       shell  should  be  placed  in a directory and the FPATH variable should
       contain the name of this directory.  They may also be specified in  the
       ENV file.

   Discipline Functions.
       Each  variable  can  have  zero or more discipline functions associated
       with it.  The shell initially understands  the  discipline  names  get,
       set,  append,  and unset but on most systems others can be added at run
       time via the C programming interface extension provided by the  builtin
       built-in  utility.  If the get discipline is defined for a variable, it
       is invoked whenever the given variable is referenced.  If the  variable
       .sh.value  is assigned a value inside the discipline function, the ref-
       erenced variable will evaluate to this value instead.  If the set  dis-
       cipline  is  defined  for  a variable, it is invoked whenever the given
       variable is assigned a value.  If the append discipline is defined  for
       a  variable,  it  is  invoked whenever a value is appended to the given
       variable.  The variable .sh.value is given the value  of  the  variable
       before  invoking  the discipline, and the variable will be assigned the
       value of .sh.value after the discipline  completes.   If  .sh.value  is
       unset  inside  the  discipline,  then  that value is unchanged.  If the
       unset discipline is defined for a variable, it is invoked whenever  the
       given  variable  is unset.  The variable will not be unset unless it is
       unset explicitly from within this discipline function.

       The variable .sh.name contains the name of the variable for  which  the
       discipline  function  is  called, .sh.subscript is the subscript of the
       variable, and .sh.value will contain the value  being  assigned  inside
       the  .set  discipline  function.   For  the  set  discipline,  changing
       .sh.value will change the value that gets assigned.

   Jobs.
       If the monitor option of the set command is turned on,  an  interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs, printed by the jobs command, and assigns them small integer  num-
       bers.   When a job is started asynchronously with &, the shell prints a
       line which looks like:

            [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       This  paragraph  and the next require features that are not in all ver-
       sions of UNIX and may not apply.  If you are running a job and wish  to
       do something else you may hit the key ^Z (control-Z) which sends a STOP
       signal to the current job.  The shell will then normally indicate  that
       the  job  has  been  ‘Stopped’, and print another prompt.  You can then
       manipulate the state of this job, putting it in the background with the
       bg  command,  or  run some other commands and then eventually bring the
       job back into the foreground with the  foreground  command  fg.   A  ^Z
       takes  effect immediately and is like an interrupt in that pending out-
       put and unread input are discarded when it is typed.

       A job being run in the background will stop if it tries  to  read  from
       the  terminal.  Background jobs are normally allowed to produce output,
       but this can be disabled by giving the command stty tostop.  If you set
       this  tty  option, then background jobs will stop when they try to pro-
       duce output like they do when they try to read input.

       There are several ways to refer to jobs in the shell.   A  job  can  be
       referred  to  by  the process id of any process of the job or by one of
       the following:
       %number
              The job with the given number.
       %string
              Any job whose command line begins with string.
       %?string
              Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous job.

       The shell learns immediately whenever a process changes state.  It nor-
       mally  informs  you  whenever  a job becomes blocked so that no further
       progress is possible, but only just before it prints a prompt.  This is
       done  so  that  it  does  not  otherwise disturb your work.  The notify
       option of the set command causes the shell to print  these  job  change
       messages as soon as they occur.

       When  the  monitor  option  is  on,  each background job that completes
       triggers any trap set for CHLD.

       When you try to leave the shell while jobs are running or stopped,  you
       will  be warned that ‘You have stopped(running) jobs.’  You may use the
       jobs command to see what they are.  If  you  immediately  try  to  exit
       again,  the shell will not warn you a second time, and the stopped jobs
       will be terminated.  When a login shell receives a HUP signal, it sends
       a  HUP  signal  to  each job that has not been disowned with the disown
       built-in command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the com-
       mand is followed by & and the monitor option is not active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each  time  a command is read, the above substitutions are carried out.
       If the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.  Next, the com-
       mand name is checked to see if it matches a user defined function.   If
       it  does,  the  positional  parameters  are saved and then reset to the
       arguments of the function call.  A function is  also  executed  in  the
       current shell process.  When the function completes or issues a return,
       the positional parameter list is restored.  For functions defined  with
       the  function  name syntax, any trap set on EXIT within the function is
       executed.  The exit value of a function is the value of the  last  com-
       mand  executed.  If a command name is not a special built-in command or
       a user defined function, but it is one of the built-in commands  listed
       below, it is executed in the current shell process.

       The  shell variable PATH defines the search path for the directory con-
       taining the command.  Alternative directory names are  separated  by  a
       colon  (:).   The  default  path  is  /bin:/usr/bin:  (specifying /bin,
       /usr/bin, and the current directory in that order).  The current direc-
       tory  can be specified by two or more adjacent colons, or by a colon at
       the beginning or end of the path list.  If the command name contains  a
       /,  then the search path is not used.  Otherwise, each directory in the
       path is searched for an executable file of the given name that is not a
       directory.   If  found,  and  if  the  shell determines that there is a
       built-in version of a command corresponding to a given  pathname,  this
       built-in  is invoked in the current process.  If found, and this direc-
       tory is also contained in the value of the FPATH  variable,  then  this
       file  is  loaded  into  the current shell environment as if it were the
       argument to the . command except that only preset aliases are expanded,
       and  a  function  of the given name is executed as described above.  If
       not found, and the file .paths is found, and the this file  contains  a
       line of the form FPATH=path where path names an existing directory, and
       this directory contains a file of the given name,  then  this  file  is
       loaded into the current shell environment as if it were the argument to
       the . special built-in command and a function of the given name is exe-
       cuted.   Otherwise,  if  found,  a process is created and an attempt is
       made to execute the command via exec(2).

       When an executable is found, the directory where  it  is  found  in  is
       searched  for  a  file named .paths.  If this file is found and it con-
       tains a line of the form BUILTIN_LIB=value , then the library named  by
       value  will be searched for as if it were an option argument to builtin
       -f, and if it contains a built-in of the specified name  this  will  be
       executed instead of a command by this name.  Otherwise, if this file is
       found and it contains a line of the form name=value  in  the  first  or
       second line, then the environment variable name is modified by prepend-
       ing the directory specified by value to the directory list.   If  value
       is not an absolute directory, then it specifies a directory relative to
       the directory that the executable was found.  If the environment  vari-
       able  name  does  not already exist it will be added to the environment
       list for the specified command.

       If the file has execute permission but is not  an  a.out  file,  it  is
       assumed  to  be  a file containing shell commands.  A separate shell is
       spawned to read it.  All non-exported variables  are  removed  in  this
       case.   If  the  shell command file doesn’t have read permission, or if
       the setuid and/or setgid bits are set on the file, then the shell  exe-
       cutes  an  agent  whose job it is to set up the permissions and execute
       the shell with the shell command file passed down as an open  file.   A
       parenthesized  command is executed in a sub-shell without removing non-
       exported variables.

   Command Re-entry.
       The text of the last HISTSIZE (default 128)  commands  entered  from  a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is used if the HISTFILE variable is not set or if the file it names  is
       not  writable.   A  shell  can  access  the commands of all interactive
       shells which use the same named HISTFILE.  The built-in command hist is
       used  to  list or edit a portion of this file.  The portion of the file
       to be edited or listed can be selected by number or by giving the first
       character  or  characters of the command.  A single command or range of
       commands can be specified.  If you do not specify an editor program  as
       an  argument  to  hist then the value of the variable HISTEDIT is used.
       If HISTEDIT is unset, the obsolete variable FCEDIT is used.  If  FCEDIT
       is not defined, then /bin/ed is used.  The edited command(s) is printed
       and re-executed upon leaving the editor unless you quit  without  writ-
       ing.   The  -s  option (and in obsolete versions, the editor name -) is
       used to skip the editing phase and to re-execute the command.  In  this
       case a substitution parameter of the form old=new can be used to modify
       the command before execution.  For example, with the  preset  alias  r,
       which  is  aliased  to hist -s, typing ‘r bad=good c’ will re-execute
       the most recent command which starts with the letter c,  replacing  the
       first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally,  each  command  line entered from a terminal device is simply
       typed followed by a new-line (‘RETURN’ or ‘LINE FEED’).  If either  the
       emacs,  gmacs,  or  vi  option is active, the user can edit the command
       line.  To be in either  of  these  edit  modes  set  the  corresponding
       option.   An  editing  option  is  automatically selected each time the
       VISUAL or EDITOR variable is assigned a value ending in either of these
       option names.

       The  editing  features require that the user’s terminal accept ‘RETURN’
       as carriage return without line feed and that a space (‘ ’) must  over-
       write the current character on the screen.

       The editing modes implement a concept where the user is looking through
       a window at the current line.  The window width is the value of COLUMNS
       if  it  is  defined, otherwise 80.  If the window width is too small to
       display the prompt and leave at least 8 columns  to  enter  input,  the
       prompt is truncated from the left.  If the line is longer than the win-
       dow width minus two, a mark is displayed at the end of  the  window  to
       notify the user.  As the cursor moves and reaches the window boundaries
       the window will be centered about the cursor.  The mark is a >  (<,  *)
       if the line extends on the right (left, both) side(s) of the window.

       The  search  commands  in  each edit mode provide access to the history
       file.  Only strings are matched, not patterns, although a leading ^  in
       the  string  restricts the match to begin at the first character in the
       line.

       Each of the edit modes has an operation to list the files  or  commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, , &, or (, and  the  word  does
       not  begin  with   or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could  match  the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.  If the partially entered word does  not  con-
       tain  any  file expansion characters, a * is appended before generating
       these lists.  After displaying the generated list, the  input  line  is
       redrawn.   These  operations  are  called command name listing and file
       name listing, respectively.  There are additional operations,  referred
       to  as  command name completion and file name completion, which compute
       the list of matching commands or files, but  instead  of  printing  the
       list,  replace  the current word with a complete or partial match.  For
       file name completion, if the match is unique, a / is  appended  if  the
       file is a directory and a space is appended if the file is not a direc-
       tory.  Otherwise, the longest common prefix for all the matching  files
       replaces  the  word.   For command name completion, only the portion of
       the file names after the last / are used to find  the  longest  command
       prefix.   If  only  a single name matches this prefix, then the word is
       replaced with the command name followed by a space.

   Key Bindings.
       The KEYBD trap can be used to intercept keys  as  they  are  typed  and
       change  the  characters that are actually seen by the shell.  This trap
       is executed after each character (or sequence of  characters  when  the
       first  character is ESC) is entered while reading from a terminal.  The
       variable .sh.edchar contains the character or character sequence  which
       generated  the  trap.   Changing  the  value  of .sh.edchar in the trap
       action causes the shell to behave as if the new value were entered from
       the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor
       at the time of the input.  The variable .sh.edmode is set to  ESC  when
       in  vi  insert  mode  (see below) and is null otherwise.  By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar  it  will  cause  the
       shell to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only  difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the  point  needing  correction  and
       then inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation  for
       control  characters  is caret (^) followed by the character.  For exam-
       ple, ^F is the notation for control F.  This is entered  by  depressing
       ‘f’  while  holding  down the ‘CTRL’ (control) key.  The ‘SHIFT’ key is
       not depressed.  (The notation ^?  indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a  character.   For
       example,  M-f  (pronounced  Meta f) is entered by depressing ESC (ascii
       033) followed by ‘f’.  (M-F would be the notation for ESC  followed  by
       ‘SHIFT’ (capital) ‘F’.)

       All  edit  commands operate from any place on the line (not just at the
       beginning).  Neither the ‘RETURN’ nor the ‘LINE FEED’  key  is  entered
       after edit commands except when noted.

       ^F        Move cursor forward (right) one character.
       M-[C      Move cursor forward (right) one character.
       M-f       Move  cursor forward one word.  (The emacs editor’s idea of a
                 word is a string of characters consisting  of  only  letters,
                 digits and underscores.)
       ^B        Move cursor backward (left) one character.
       M-[D      Move cursor backward (left) one character.
       M-b       Move cursor backward one word.
       ^A        Move cursor to start of line.
       M-[H      Move cursor to start of line.
       ^E        Move cursor to end of line.
       M-[Y      Move cursor to end of line.
       ^]char    Move cursor forward to character char on current line.
       M-^]char  Move cursor backward to character char on current line.
       ^X^X      Interchange the cursor and mark.
       erase     (User  defined erase character as defined by the stty(1) com-
                 mand, usually ^H or #.)  Delete previous character.
       ^D        Delete current character.
       M-d       Delete current word.
       M-^H      (Meta-backspace) Delete previous word.
       M-h       Delete previous word.
       M-^?      (Meta-DEL) Delete previous word (if your interrupt  character
                 is ^?  (DEL, the default) then this command will not work).
       ^T        Transpose  current  character  with  previous  character  and
                 advance the cursor in emacs  mode.   Transpose  two  previous
                 characters in gmacs mode.
       ^C        Capitalize current character.
       M-c       Capitalize current word.
       M-l       Change the current word to lower case.
       ^K        Delete  from  the cursor to the end of the line.  If preceded
                 by a numerical parameter whose value is less than the current
                 cursor  position,  then  delete from given position up to the
                 cursor.  If preceded by a numerical parameter whose value  is
                 greater  than  the  current cursor position, then delete from
                 cursor up to given cursor position.
       ^W        Kill from the cursor to the mark.
       M-p       Push the region from the cursor to the mark on the stack.
       kill      (User defined kill character as defined by the stty  command,
                 usually ^G or @.)  Kill the entire current line.  If two kill
                 characters are entered in  succession,  all  kill  characters
                 from  then on cause a line feed (useful when using paper ter-
                 minals).
       ^Y        Restore last item removed from line. (Yank item back  to  the
                 line.)
       ^L        Line feed and print current line.
       ^@        (Null character) Set mark.
       M-space   (Meta space) Set mark.
       ^J        (New line) Execute the current line.
       ^M        (Return) Execute the current line.
       eof       End-of-file  character,  normally ^D, is processed as an End-
                 of-file only if the current line is null.
       ^P        Fetch previous command.  Each time ^P is entered the previous
                 command  back  in time is accessed.  Moves back one line when
                 not on the first line of a multi-line command.
       M-[A      Equivalent to ^P.
       M-<       Fetch the least recent (oldest) history line.
       M->       Fetch the most recent (youngest) history line.
       ^N        Fetch next command line.  Each time ^N is  entered  the  next
                 command line forward in time is accessed.
       M-[B      Equivalent to ^N.
       ^Rstring  Reverse search history for a previous command line containing
                 string.  If a parameter of zero is given, the search is  for-
                 ward.   String is terminated by a ‘RETURN’ or ‘NEW LINE’.  If
                 string is preceded by a ^, the matched line must  begin  with
                 string.   If  string  is  omitted, then the next command line
                 containing the most recent string is accessed.  In this  case
                 a parameter of zero reverses the direction of the search.
       ^O        Operate  -  Execute  the current line and fetch the next line
                 relative to current line from the history file.
       M-digits  (Escape) Define numeric parameter, the digits are taken as  a
                 parameter  to  the  next command.  The commands that accept a
                 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
                 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter  Soft-key  -  Your  alias list is searched for an alias by the
                 name _letter and if an alias of this  name  is  defined,  its
                 value  will  be inserted on the input queue.  The letter must
                 not be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an  alias  by  the
                 name  __letter  and  if an alias of this name is defined, its
                 value will be inserted on the input queue.  The can  be  used
                 to program functions keys on many terminals.
       M-.       The  last  word  of  the  previous command is inserted on the
                 line.  If preceded by a numeric parameter, the value of  this
                 parameter  determines  which  word  to insert rather than the
                 last word.
       M-_       Same as M-..
       M-*       Attempt file name generation on the current word.  An  aster-
                 isk is appended if the word doesn’t match any file or contain
                 any special pattern characters.
       M-ESC     Command or file name completion as described above.
       ^I        Command or file name completion as described above.
       M-=       If not preceded by a numeric parameter, it generates the list
                 of  matching commands or file names as described above.  Oth-
                 erwise, the word under the cursor is  replaced  by  the  item
                 corresponding  to the value of the numeric parameter from the
                 most recently generated command or file list.  If the  cursor
                 is not on a word, it is inserted instead.
       ^U        Multiply parameter of next command by 4.
       \         Escape next character.  Editing characters, the user’s erase,
                 kill and interrupt (normally ^?)  characters may  be  entered
                 in  a  command line or in a search string if preceded by a \.
                 The \ removes the next character’s editing features (if any).
       ^V        Display version of the shell.
       M-#       If  the  line does not begin with a #, a # is inserted at the
                 beginning of the line and after each new-line, and  the  line
                 is entered.  This causes a comment to be inserted in the his-
                 tory file.  If the line begins with a #, the # is deleted and
                 one # after each new-line is also deleted.

   Vi Editing Mode.
       There  are  two  typing modes.  Initially, when you enter a command you
       are in the input mode.  To edit, the user enters control mode by typing
       ESC (033) and moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.   Most  control  com-
       mands accept an optional repeat count prior to the command.

       When  in  vi  mode  on  most systems, canonical processing is initially
       enabled and the command will be echoed again if the speed is 1200  baud
       or greater and it contains any control characters or less than one sec-
       ond has elapsed since the prompt was printed.  The ESC character termi-
       nates  canonical  processing  for  the remainder of the command and the
       user can then modify the command line.  This scheme has the  advantages
       of canonical processing with the type-ahead echoing of raw mode.

       If  the option viraw is also set, the terminal will always have canoni-
       cal processing disabled.  This mode is implicit for systems that do not
       support  two  alternate  end of line delimiters, and may be helpful for
       certain terminals.

        Input Edit Commands
              By default the editor is in input mode.
              erase     (User defined erase character as defined by  the  stty
                        command, usually ^H or #.)  Delete previous character.
              ^W        Delete the previous blank  separated  word.   On  some
                        systems  the  viraw option may be required for this to
                        work.
              eof       As the first character of the line causes the shell to
                        terminate  unless the ignoreeof option is set.  Other-
                        wise this character is ignored.
              ^V        Escape next character.   Editing  characters  and  the
                        user’s  erase  or  kill characters may be entered in a
                        command line or in a search string if  preceded  by  a
                        ^V.   The ^V removes the next character’s editing fea-
                        tures (if any).  On some systems the viraw option  may
                        be required for this to work.
              \         Escape the next erase or kill character.
        Motion Edit Commands
              These commands will move the cursor.
              [count]l  Cursor forward (right) one character.
              [count][C Cursor forward (right) one character.
              [count]w  Cursor forward one alpha-numeric word.
              [count]W  Cursor  to the beginning of the next word that follows
                        a blank.
              [count]e  Cursor to end of word.
              [count]E  Cursor to end of the current blank delimited word.
              [count]h  Cursor backward (left) one character.
              [count][D Cursor backward (left) one character.
              [count]b  Cursor backward one word.
              [count]B  Cursor to preceding blank separated word.
              [count]  Cursor to column count.
              [count]fc Find the next character c in the current line.
              [count]Fc Find the previous character c in the current line.
              [count]tc Equivalent to f followed by h.
              [count]Tc Equivalent to F followed by l.
              [count];  Repeats count times, the last  single  character  find
                        command, f, F, t, or T.
              [count],  Reverses  the last single character find command count
                        times.
              0         Cursor to start of line.
              ^         Cursor to start of line.
              [H        Cursor to first non-blank character in line.
              $         Cursor to end of line.
              [Y        Cursor to end of line.
              %         Moves to balancing (, ), {, }, [, or ].  If cursor  is
                        not  on  one of the above characters, the remainder of
                        the line is searched for the first occurrence  of  one
                        of the above characters first.
        Search Edit Commands
              These commands access your command history.
              [count]k  Fetch  previous  command.   Each time k is entered the
                        previous command back in time is accessed.
              [count]-  Equivalent to k.
              [count][A Equivalent to k.
              [count]j  Fetch next command.  Each time j is entered  the  next
                        command forward in time is accessed.
              [count]+  Equivalent to j.
              [count][B Equivalent to j.
              [count]G  The  command  number count is fetched.  The default is
                        the least recent history command.
              /string   Search backward through history for a previous command
                        containing string.  String is terminated by a ‘RETURN’
                        or ‘NEW LINE’.  If string is  preceded  by  a  ^,  the
                        matched  line  must  begin  with string.  If string is
                        null, the previous string will be used.
              ?string   Same as / except that search will be  in  the  forward
                        direction.
              n         Search  for  next  match of the last pattern to / or ?
                        commands.
              N         Search for next match of the last pattern to /  or  ?,
                        but in reverse direction.
        Text Modification Edit Commands
              These commands will modify the line.
              a         Enter  input  mode  and  enter  text after the current
                        character.
              A         Append text to the end of the line.  Equivalent to $a.
              [count]cmotion
              c[count]motion
                        Delete  current  character  through the character that
                        motion would move the cursor to and enter input  mode.
                        If  motion  is  c, the entire line will be deleted and
                        input mode entered.
              C         Delete the current character through the end  of  line
                        and enter input mode.  Equivalent to c$.
              S         Equivalent to cc.
              [count]s  Replace characters under the cursor in input mode.
              D         Delete  the current character through the end of line.
                        Equivalent to d$.
              [count]dmotion
              d[count]motion
                        Delete current character through  the  character  that
                        motion  would  move  to.   If motion is d , the entire
                        line will be deleted.
              i         Enter input mode and insert text  before  the  current
                        character.
              I         Insert text before the beginning of the line.  Equiva-
                        lent to 0i.
              [count]P  Place the previous text modification before  the  cur-
                        sor.
              [count]p  Place the previous text modification after the cursor.
              R         Enter input mode and replace characters on the  screen
                        with characters you type overlay fashion.
              [count]rc Replace the count character(s) starting at the current
                        cursor position with c, and advance the cursor.
              [count]x  Delete current character.
              [count]X  Delete preceding character.
              [count].  Repeat the previous text modification command.
              [count]  Invert the case of the count character(s) starting  at
                        the current cursor position and advance the cursor.
              [count]_  Causes  the  count  word of the previous command to be
                        appended and input mode entered.   The  last  word  is
                        used if count is omitted.
              *         Causes  an  *  to  be appended to the current word and
                        file name generation attempted.  If no match is found,
                        it rings the bell.  Otherwise, the word is replaced by
                        the matching pattern and input mode is entered.
              \         Command or file name completion as described above.
              ^I        Command or file name completion as described above.
        Other Edit Commands
              Miscellaneous commands.
              [count]ymotion
              y[count]motion
                        Yank current character through character  that  motion
                        would move the cursor to and puts them into the delete
                        buffer.  The text and cursor are unchanged.
              yy        Yanks the entire line.
              Y         Yanks from current position to end of  line.   Equiva-
                        lent to y$.
              u         Undo the last text modifying command.
              U         Undo  all the text modifying commands performed on the
                        line.
              [count]v  Returns the command hist  -e  ${VISUAL:-${EDITOR:-vi}}
                        count  in the input buffer.  If count is omitted, then
                        the current line is used.
              ^L        Line feed and print current line.  Has effect only  in
                        control mode.
              ^J        (New line)  Execute  the  current  line, regardless of
                        mode.
              ^M        (Return) Execute the current line, regardless of mode.
              #         If  the  first  character  of the command is a #, then
                        this command deletes this # and each # that follows  a
                        newline.   Otherwise, sends the line after inserting a
                        # in front of each line in the  command.   Useful  for
                        causing the current line to be inserted in the history
                        as a comment  and  uncommenting  previously  commented
                        commands in the history file.
              [count]=  If  count  is  not specified, it generates the list of
                        matching commands or file names  as  described  above.
                        Otherwise,  the  word under the the cursor is replaced
                        by the count item from  the  most  recently  generated
                        command or file list.  If the cursor is not on a word,
                        it is inserted instead.
              @letter   Your alias list is searched for an alias by  the  name
                        _letter  and  if an alias of this name is defined, its
                        value will be inserted on the input queue for process-
                        ing.
              ^V        Display version of the shell.

   Built-in Commands.
       The  following  simple-commands  are  executed  in  the  shell process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output  is written on file descriptor 1 and the exit status, when there
       is no syntax error, is zero.  Except for :, true, false, echo,  newgrp,
       and  login, all built-in commands accept -- to indicate end of options.
       They also interpret the option --man as a request to  display  the  man
       page onto standard error and -?  as a help request which prints a usage
       message on standard error.  Commands that are preceded by one or two  †
       symbols  are special built-in commands and are treated specially in the
       following ways:
       1.     Variable assignment lists preceding the command remain in effect
              when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words  following a command preceded by †† that are in the format
              of a variable assignment are expanded with the same rules  as  a
              variable assignment.  This means that tilde substitution is per-
              formed after the = sign and field splitting and file name gener-
              ation are not performed.

       † : [ arg ... ]
              The command only expands parameters.

       † . name [ arg ... ]
              If  name  is  a function defined with the function name reserved
              word syntax, the function is executed in the current environment
              (as  if  it had been defined with the name() syntax.)  Otherwise
              if name refers to a file, the file is read in its  entirety  and
              the commands are executed in the current shell environment.  The
              search path specified by PATH is used to find the directory con-
              taining  the  file.  If any arguments arg are given, they become
              the positional parameters while processing the  .   command  and
              the original positional parameters are restored upon completion.
              Otherwise the positional parameters  are  unchanged.   The  exit
              status is the exit status of the last command executed.

       †† alias [ -ptx ]  [ name[ =value  ] ] ...
              alias  with  no arguments prints the list of aliases in the form
              name=value on standard output.  The -p option  causes  the  word
              alias  to  be  inserted before each one.  When one or more argu-
              ments are given, an alias is defined for each name  whose  value
              is  given.  A trailing space in value causes the next word to be
              checked for alias substitution.  The obsolete -t option is  used
              to  set  and list tracked aliases.  The value of a tracked alias
              is the full pathname corresponding to the given name.  The value
              becomes  undefined when the value of PATH is reset but the alias
              remains tracked.  Without the -t option, for each  name  in  the
              argument list for which no value is given, the name and value of
              the alias is printed.  The obsolete -x  option  has  no  effect.
              The  exit  status  is non-zero if a name is given, but no value,
              and no alias has been defined for the name.

       bg [ job... ]
              This command is only on systems that support job control.   Puts
              each  specified job into the background.  The current job is put
              in the background if job is  not  specified.   See  Jobs  for  a
              description of the format of job.

       † break [ n ]
              Exit  from  the  enclosing for, while, until, or select loop, if
              any.  If n is specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
              If name is not specified, and no -f  option  is  specified,  the
              built-ins  are printed on standard output.  The -s option prints
              only the special built-ins.  Otherwise, each name represents the
              pathname  whose basename is the name of the built-in.  The entry
              point function name is determined by prepending b_ to the built-
              in  name.   Special  built-ins  cannot be bound to a pathname or
              deleted.  The -d option deletes each of the given built-ins.  On
              systems  that  support  dynamic  loading,  the -f option names a
              shared library containing the code for  built-ins.   The  shared
              library prefix and/or suffix, which depend on the system, can be
              omitted.  Once a library is loaded, its symbols become available
              for  subsequent  invocations of builtin.  Multiple libraries can
              be specified with separate invocations of the  builtin  command.
              Libraries  are  searched  in the reverse order in which they are
              specified.  When a library is loaded, it looks for a function in
              the  library  whose name is lib_init() and invokes this function
              with an argument of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
              This command can be in either of two forms.  In the  first  form
              it changes the current directory to arg.  If arg is - the direc-
              tory is changed to the previous directory.  The  shell  variable
              HOME is the default arg.  The variable PWD is set to the current
              directory.  The shell variable CDPATH defines  the  search  path
              for  the  directory containing arg.  Alternative directory names
              are separated by a colon (:).  The default path is <null> (spec-
              ifying  the current directory).  Note that the current directory
              is specified by a null path name, which can  appear  immediately
              after  the  equal  sign or between the colon delimiters anywhere
              else in the path list.  If arg begins with a / then  the  search
              path  is  not  used.   Otherwise,  each directory in the path is
              searched for arg.
              The second form of cd substitutes the string new for the  string
              old  in  the current directory name, PWD, and tries to change to
              this new directory.
              By default, symbolic link names are treated literally when find-
              ing  the  directory  name.  This is equivalent to the -L option.
              The -P option causes symbolic links to be resolved  when  deter-
              mining the directory.  The last instance of -L or -P on the com-
              mand line determines which method is used.
              The cd command may not be executed by rksh.

       command [ -pvxV ] name [ arg ... ]
              Without the -v or -V options, command  executes  name  with  the
              arguments  given by arg.  The -p option causes a default path to
              be searched rather than the one defined by the  value  of  PATH.
              Functions  will not be searched for when finding name.  In addi-
              tion, if name refers to a special built-in, none of the  special
              properties  associated with the leading daggers will be honored.
              (For example, the predefined alias redirect=command exec  pre-
              vents  a  script from terminating when an invalid redirection is
              given.)  With the -x option, if command execution  would  result
              in  a failure because there are too many arguments, errno E2BIG,
              the shell will invoke command name multiple times with a  subset
              of the arguments on each invocation.  Arguments that occur prior
              to the first word that expands to multiple arguments  and  after
              the  last word that expands to multiple arguments will be passed
              on each invocation.  The exit status will be the maximum invoca-
              tion  exit status.  With the -v option, command is equivalent to
              the built-in whence command  described  below.   The  -V  option
              causes command to act like whence -v.

       † continue [ n ]
              Resume the next iteration of the enclosing for, while, until, or
              select loop.  If n is specified, then resume at the n-th enclos-
              ing loop.

       disown [ job... ]
              Causes  the shell not to send a HUP signal to each given job, or
              all active jobs if job is omitted, when  a  login  shell  termi-
              nates.

       echo [ arg ... ]
              When  the  first  arg  does  not begin with a -, and none of the
              arguments contain a \, then echo prints each  of  its  arguments
              separated  by  a space and terminated by a new-line.  Otherwise,
              the behavior of echo is system dependent  and  print  or  printf
              described  below  should  be  used.   See  echo(1) for usage and
              description.

       † eval [ arg ... ]
              The arguments are read as input to the shell and  the  resulting
              command(s) executed.

       † exec [ -c ] [ -a name ] [ arg ... ]
              If  arg is given, the command specified by the arguments is exe-
              cuted in place of this shell without  creating  a  new  process.
              The -c option causes the environment to be cleared before apply-
              ing variable assignments associated with  the  exec  invocation.
              The  -a  option causes name rather than the first arg, to become
              argv[0] for the new process.  Input/output arguments may  appear
              and affect the current process.  If arg is not given, the effect
              of this command is to modify file descriptors as  prescribed  by
              the  input/output  redirection  list.   In  this  case, any file
              descriptor numbers greater than 2  that  are  opened  with  this
              mechanism are closed when invoking another program.

       † exit [ n ]
              Causes  the  shell  to exit with the exit status specified by n.
              The value will be the least significant 8 bits of the  specified
              status.   If  n  is omitted, then the exit status is that of the
              last command executed.  An end-of-file will also cause the shell
              to  exit  except for a shell which has the ignoreeof option (see
              set below) turned on.

       †† export [ -p ] [ name[=value] ] ...
              If name is not given, the names and values of each variable with
              the  export  attribute  are  printed with the values quoted in a
              manner that allows them to be re-input.  The  -p  option  causes
              the  word export to be inserted before each one.  Otherwise, the
              given names are marked for automatic export to  the  environment
              of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
              This  command is only on systems that support job control.  Each
              job specified is brought to the foreground and waited for in the
              specified order.  Otherwise, the current job is brought into the
              foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
              Prints the current value of the configuration parameter given by
              name.   The  configuration  parameters  are  defined by the IEEE
              POSIX 1003.1 and IEEE POSIX 1003.2 standards.  (See  pathconf(2)
              and  sysconf(2).)  The pathname argument is required for parame-
              ters whose value depends on the location in the file system.  If
              no  arguments  are given, getconf prints the names and values of
              the current configuration parameters.  The pathname  /  is  used
              for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
              Checks arg for legal options.  If arg is omitted, the positional
              parameters are used.  An option argument begins with a + or a -.
              An  option not beginning with + or - or the argument -- ends the
              options.  optstring contains the  letters  that  getopts  recog-
              nizes.   If a letter is followed by a :, that option is expected
              to have an argument.  The options  can  be  separated  from  the
              argument by blanks.  The option -?  causes getopts to generate a
              usage message on standard error.  The -a argument can be used to
              specify the name to use for the usage message, which defaults to
              $0.
              getopts places the next option letter it finds  inside  variable
              vname  each  time  it  is  invoked.   The  option letter will be
              prepended with a + when arg begins with a +.  The index  of  the
              next arg is stored in OPTIND.  The option argument, if any, gets
              stored in OPTARG.
              A leading : in optstring causes getopts to store the  letter  of
              an  invalid  option  in  OPTARG,  and  to set vname to ?  for an
              unknown option and to : when a required option argument is miss-
              ing.  Otherwise, getopts prints an error message.  The exit sta-
              tus is non-zero when there are no more options.
              There is no way to specify any of the options :, +, -, ?, [, and
              ].  The option # can only be specified as the first option.

       hist [ -e ename  ] [ -nlr ] [ first [ last ] ]
       hist -s  [ old=new ] [ command ]
              In  the  first  form,  a range of commands from first to last is
              selected from the last HISTSIZE commands that were typed at  the
              terminal.   The  arguments  first and last may be specified as a
              number or as a string.  A string is  used  to  locate  the  most
              recent  command starting with the given string.  A negative num-
              ber is used as an offset to the current command number.  If  the
              -l  option is selected, the commands are listed on standard out-
              put.  Otherwise, the editor program ename is invoked on  a  file
              containing  these  keyboard commands.  If ename is not supplied,
              then the value of the variable HISTEDIT is used.  If HISTEDIT is
              not  set,  then  FCEDIT (default /bin/ed) is used as the editor.
              When editing is complete, the edited command(s) is  executed  if
              the  changes have been saved.  If last is not specified, then it
              will be set to first.  If first is not specified, the default is
              the  previous  command  for  editing  and  -16 for listing.  The
              option -r reverses the order of the commands and the  option  -n
              suppresses  command  numbers  when listing.  In the second form,
              command is interpreted as first described above and defaults  to
              the  last  command  executed.  The resulting command is executed
              after the optional substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
              Lists information about each given job; or all  active  jobs  if
              job  is omitted.  The -l option lists process ids in addition to
              the normal information.  The -n option only displays  jobs  that
              have  stopped  or  exited  since  last  notified.  The -p option
              causes only the process group to be  listed.   See  Jobs  for  a
              description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -l [ sig ... ]
              Sends either the TERM (terminate) signal or the specified signal
              to the specified jobs or processes.  Signals are either given by
              number  with  the  -n  option  or by name with the -s option (as
              given in <signal.h>, stripped of the  prefix  ‘‘SIG’’  with  the
              exception  that SIGCLD is named CHLD).  For backward compatibil-
              ity, the n and s can be omitted and the number  or  name  placed
              immediately after the -.  If the signal being sent is TERM (ter-
              minate) or HUP (hangup), then the job or process will be sent  a
              CONT  (continue)  signal if it is stopped.  The argument job can
              be the process id of a process that is not a member  of  one  of
              the  active  jobs.   See Jobs for a description of the format of
              job.  In the third form, kill -l, if sig is not  specified,  the
              signal  names  are  listed.   Otherwise,  for each sig that is a
              name, the corresponding signal number is listed.  For  each  sig
              that  is  a  number,  the signal name corresponding to the least
              significant 8 bits of sig is listed.

       let arg ...
              Each arg is a separate arithmetic expression  to  be  evaluated.
              See Arithmetic Evaluation above, for a description of arithmetic
              expression evaluation.
              The exit status is 0 if the value of the last expression is non-
              zero, and 1 otherwise.

       † newgrp [ arg ... ]
              Equivalent to exec /bin/newgrp arg ....

       print [ -Renprs ] [ -u unit] [ -f format ] [ arg ... ]
              With  no  options or with option - or --, each arg is printed on
              standard output.  The -f  option  causes  the  arguments  to  be
              printed  as  described  by printf.  In this case, any e, n, r, R
              options are ignored.  Otherwise, unless the -R or -r, are speci-
              fied, the following escape conventions will be applied:
              \a     The alert character (ascii 07).
              \b     The backspace character (ascii 010).
              \c     Causes print to end without processing more arguments and
                     not adding a new-line.
              \f     The formfeed character (ascii 014).
              \n     The new-line character (ascii 012).
              \r     The carriage return character (ascii 015).
              \t     The tab character (ascii 011).
              \v     The vertical tab character (ascii 013).
              \E     The escape character (ascii 033).
              \\     The backslash character \.
              \0x    The character defined by  the  1,  2,  or  3-digit  octal
                     string given by x.

              The  -R  option  will print all subsequent arguments and options
              other than -n.  The -e causes the above escape conventions to be
              applied This is the default behavior.  It reverses the effect of
              an earlier -r.  The -p option causes the arguments to be written
              onto the pipe of the process spawned with & instead of standard
              output.  The -s option causes the arguments to be  written  onto
              the  history file instead of standard output.  The -u option can
              be used to specify a one digit file descriptor unit number  unit
              on  which  the output will be placed.  The default is 1.  If the
              option -n is used, no new-line is added to the output.

       printf format [ arg ... ]
              The arguments arg are printed on standard output  in  accordance
              with  the  ANSI-C  formatting  rules  associated with the format
              string format.  If the number of arguments exceeds the number of
              format  specifications,  the  format  string is reused to format
              remaining arguments.  The following extensions can also be used:
              A  %b format can be used instead of %s to cause escape sequences
              in the corresponding arg to be expanded as described  in  print.
              A  %B option causes each of the arguments to be treated as vari-
              able names and the binary value of  variable  will  be  printed.
              This  is  most useful for variables whose attribute is -b.  A %H
              format can be used instead of %s to cause characters in arg that
              are  special  in HTML and XML to be output to be output as their
              entity name.  A %P format can be used instead of %s to cause arg
              to  be  interpreted  as  an  extended  regular expression and be
              printed as a shell pattern.  A %R format can be used instead  of
              %s to cause arg interpreted as a shell pattern and to be printed
              as an extended regular expression.  A  %q  format  can  be  used
              instead  of  %s  to cause the resulting string to be quoted in a
              manner than can be reinput to the shell.  A %(date-format)T for-
              mat can be use to treat an argument as a date/time string and to
              format the date/time according to the date-format as defined for
              the date(1) command.  A %Z format will output a byte whose value
              is 0.  The precision field of the %d format can be followed by a
              .  and the output base.

       pwd [ -LP ]
              Outputs  the  value  of  the  current working directory.  The -L
              option is the default; it prints the logical name of the current
              directory.   If  the  -P option is given, all symbolic links are
              resolved from the name.  The last instance of -L or  -P  on  the
              command line determines which method is used.

       read [ -Aprs ] [ -d delim] [ -n n] [ [ -N n] [ [ -t timeout] [ -u unit]
       [ vname?prompt ] [ vname ... ]
              The  shell  input  mechanism.  One line is read and is broken up
              into fields using the characters  in  IFS  as  separators.   The
              escape  character,  \, is used to remove any special meaning for
              the next character and for line  continuation.   The  -d  option
              causes  the  read  to  continue  to the first character of delim
              rather than new-line.  The -n option causes at most n  bytes  to
              read rather a full line but will return when reading from a slow
              device as soon as any characters have been read.  The -N  option
              causes  exactly  n  to  be  read  unless an end-of-file has been
              encountered or the read times out because of the -t option.   In
              raw  mode,  -r,  the  \ character is not treated specially.  The
              first field is assigned to the first vname, the second field  to
              the  second  vname,  etc.,  with leftover fields assigned to the
              last vname.  When vname has the binary attribute and -n or -N is
              specified,  the bytes that are read are stored directly into the
              variable.  The -A option causes the variable vname to  be  unset
              and  each field that is read to be stored in successive elements
              of the indexed array vname.  The -p option causes the input line
              to  be  taken  from  the  input pipe of a process spawned by the
              shell using &.  If the -s option is present, the input will  be
              saved  as  a  command in the history file.  The option -u can be
              used to specify a one digit file descriptor unit  unit  to  read
              from.   The  file descriptor can be opened with the exec special
              built-in command.  The default value of unit n is 0.  The option
              -t  is  used to specify a timeout in seconds when reading from a
              terminal or pipe.  If vname is omitted, then REPLY  is  used  as
              the  default  vname.   An  end-of-file with the -p option causes
              cleanup for this process so that another can be spawned.  If the
              first  argument contains a ?, the remainder of this word is used
              as a prompt on standard error when  the  shell  is  interactive.
              The  exit  status  is  0 unless an end-of-file is encountered or
              read has timed out.

       †† readonly [ -p ] [ vname[=value] ] ...
              If vname is not given, the names and  values  of  each  variable
              with the readonly attribute is printed with the values quoted in
              a manner that allows them to  be  re-inputted.   The  -p  option
              causes the word readonly to be inserted before each one.  Other-
              wise, the given vnames are marked readonly and these names  can-
              not be changed by subsequent assignment.

       † return [ n ]
              Causes  a  shell function or .  script to return to the invoking
              script with the exit status specified by n.  The value  will  be
              the  least  significant 8 bits of the specified status.  If n is
              omitted, then the return status is that of the last command exe-
              cuted.   If  return  is  invoked  while not in a function or a .
              script, then it behaves the same as exit.

       † set [ CGabefhkmnopstuvx ] [ o [ option ] ] ... [ A vname ]  [  arg
       ... ]
              The options for this command have meaning as follows:
              -A      Array assignment.  Unset the variable vname  and  assign
                      values  sequentially  from the arg list.  If +A is used,
                      the variable vname is not unset first.
              -C      Prevents redirection > from truncating  existing  files.
                      Files  that are created are opened with the O_EXCL mode.
                      Requires > to truncate a file when turned on.
              -G      Causes the pattern  by itself to match files and  zero
                      or  more  directories  and sub-directories when used for
                      file name generation.  If followed by a / only  directo-
                      ries and sub-directories are matched.
              -a      All  subsequent variables that are defined are automati-
                      cally exported.
              -b      Prints job completion messages as soon as  a  background
                      job  changes  state  rather  than  waiting  for the next
                      prompt.
              -e      If a command has a non-zero exit status, execute the ERR
                      trap,  if  set,  and  exit.  This mode is disabled while
                      reading profiles.
              -f      Disables file name generation.
              -h      Each command becomes a tracked alias when first  encoun-
                      tered.
              -k      (Obsolete). All variable assignment arguments are placed
                      in the environment for a command, not  just  those  that
                      precede the command name.
              -m      Background jobs will run in a separate process group and
                      a line will print upon completion.  The exit  status  of
                      background jobs is reported in a completion message.  On
                      systems with job control, this option is turned on auto-
                      matically for interactive shells.
              -n      Read  commands  and check them for syntax errors, but do
                      not execute them.  Ignored for interactive shells.
              -o      The following argument  can  be  one  of  the  following
                      option names:
                      allexport
                              Same as -a.
                      errexit Same as -e.
                      bgnice  All background jobs are run at a lower priority.
                              This is the default mode.
                      emacs   Puts you in an emacs style  in-line  editor  for
                              command entry.
                      globstar
                              Same as -G.
                      gmacs   Puts  you  in  a  gmacs style in-line editor for
                              command entry.
                      ignoreeof
                              The shell will not  exit  on  end-of-file.   The
                              command exit must be used.
                      keyword Same as -k.
                      markdirs
                              All  directory  names  resulting  from file name
                              generation have a trailing / appended.
                      monitor Same as -m.
                      noclobber
                              Same as -C.
                      noexec  Same as -n.
                      noglob  Same as -f.
                      nolog   Do not save function definitions in the  history
                              file.
                      notify  Same as -b.
                      nounset Same as -u.
                      pipefail
                              A  pipeline  will  not complete until all compo-
                              nents of the pipeline have  completed,  and  the
                              return  value will be the value of the last non-
                              zero command to fail or zero of no  command  has
                              failed.
                      privileged
                              Same as -p.
                      verbose Same as -v.
                      trackall
                              Same as -h.
                      vi      Puts  you  in  insert mode of a vi style in-line
                              editor until you hit the escape  character  033.
                              This  puts  you in control mode.  A return sends
                              the line.
                      viraw   Each character is processed as it is typed in vi
                              mode.
                      xtrace  Same as -x.
                      If  no  option name is supplied, then the current option
                      settings are printed.
              -p      Disables  processing of the $HOME/.profile file and uses
                      the file /etc/suid_profile  instead  of  the  ENV  file.
                      This  mode is on whenever the effective uid (gid) is not
                      equal to the real uid (gid).  Turning  this  off  causes
                      the  effective uid and gid to be set to the real uid and
                      gid.
              -s      Sort the positional parameters lexicographically.
              -t      (Obsolete).  Exit after reading and executing  one  com-
                      mand.
              -u      Treat unset parameters as an error when substituting.
              -v      Print shell input lines as they are read.
              -x      Print commands and their arguments as they are executed.
              --      Do not change any of the options; useful in  setting  $1
                      to  a  value  beginning  with -.  If no arguments follow
                      this option then the positional parameters are unset.

              As an obsolete feature, if the first arg is - then the -x and -v
              options  are turned off and the next arg is treated as the first
              argument.  Using + rather than -  causes  these  options  to  be
              turned  off.   These options can also be used upon invocation of
              the shell.  The current set of  options  may  be  found  in  $-.
              Unless  -A  is specified, the remaining arguments are positional
              parameters and are assigned, in order, to  $1  $2  ....   If  no
              arguments  are given, then the names and values of all variables
              are printed on the standard output.

       † shift [ n ]
              The positional parameters from $n+1 ...  are renamed  $1  ...  ,
              default  n  is 1.  The parameter n can be any arithmetic expres-
              sion that evaluates to a non-negative number less than or  equal
              to $#.

       sleep seconds
              Suspends  execution  for  the number of decimal seconds or frac-
              tions of a second given by seconds.

       † trap [ -p ] [ action ] [ sig ] ...
              The -p option causes the trap action associated with  each  trap
              as  specified  by  the  arguments to be printed with appropriate
              quoting.  Otherwise, action will be processed as if it  were  an
              argument  to  eval  when the shell receives signal(s) sig.  Each
              sig can be given as a number or as the name of the signal.  Trap
              commands are executed in order of signal number.  Any attempt to
              set a trap on a signal that was ignored on entry to the  current
              shell is ineffective.  If action is omitted and the first sig is
              a number, or if action is -, then the trap(s) for each  sig  are
              reset  to  their  original values.  If action is the null string
              then this signal is ignored by the shell and by the commands  it
              invokes.   If sig is ERR then action will be executed whenever a
              command has a non-zero exit status.  If sig is DEBUG then action
              will  be executed before each command.  The variable .sh.command
              will contain the contents  of  the  current  command  line  when
              action  is  running.  If sig is 0 or EXIT and the trap statement
              is executed inside the body of a function defined with the func-
              tion  name syntax, then the command action is executed after the
              function completes.  If sig is 0 or EXIT for a trap set  outside
              any  function  then  the command action is executed on exit from
              the shell.  If sig is KEYBD, then action will be executed  when-
              ever  a key is read while in emacs, gmacs, or vi mode.  The trap
              command with no arguments prints a list of  commands  associated
              with each signal number.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       †† typeset [ AHflbnprtux ] [ EFLRZi[n] ]  [ vname[=value ]  ] ...
              Sets  attributes  and  values for shell variables and functions.
              When invoked inside a function defined with  the  function  name
              syntax, a new instance of the variable vname is created, and the
              variable’s value and type are restored when  the  function  com-
              pletes.  The following list of attributes may be specified:
              -A     Declares  vname  to  be an associative array.  Subscripts
                     are strings rather than arithmetic expressions.
              -E     Declares vname to be a double  precision  floating  point
                     number.   If n is non-zero, it defines the number of sig-
                     nificant figures that  are  used  when  expanding  vname.
                     Otherwise, ten significant figures will be used.
              -F     Declares  vname  to  be a double precision floating point
                     number.  If n is  non-zero,  it  defines  the  number  of
                     places after the decimal point that are used when expand-
                     ing vname.  Otherwise ten places after the decimal  point
                     will be used.
              -H     This  option  provides  UNIX to host-name file mapping on
                     non-UNIX machines.
              -L     Left justify and remove leading blanks from value.  If  n
                     is non-zero, it defines the width of the field, otherwise
                     it is determined by the  width  of  the  value  of  first
                     assignment.   When  the  variable  is  assigned to, it is
                     filled on the right with blanks or truncated,  if  neces-
                     sary,  to  fit  into  the field.  The -R option is turned
                     off.
              -R     Right justify and fill with leading blanks.  If n is non-
                     zero,  it defines the width of the field, otherwise it is
                     determined by the width of the value of first assignment.
                     The  field  is  left filled with blanks or truncated from
                     the end if the variable is reassigned.  The -L option  is
                     turned off.
              -Z     Right  justify  and  fill with leading zeros if the first
                     non-blank character is a digit and the -L option has  not
                     been  set.  Remove leading zeros if the -L option is also
                     set.  If n is non-zero,  it  defines  the  width  of  the
                     field,  otherwise  it  is  determined by the width of the
                     value of first assignment.
              -f     The names refer to function names  rather  than  variable
                     names.   No  assignments  can  be made and the only other
                     valid options are -t, -u and -x.  The -t option turns  on
                     execution  tracing  for  this  function.   The  -u option
                     causes this function to be marked undefined.   The  FPATH
                     variable will be searched to find the function definition
                     when the function is referenced.   If  no  options  other
                     than  -f  is specified, then the function definition will
                     be displayed on standard output.   If  +f  is  specified,
                     then  a  line  containing the function name followed by a
                     shell comment containing the line number and path name of
                     the file where this function was defined, if any, is dis-
                     played.
              -b     The variable can hold any number of bytes of  data.   The
                     data  can be text or binary.  The value is represented by
                     the base64 encoding of the data.  If -Z  is  also  speci-
                     fied, the size in bytes of the data in the buffer will be
                     determined by the size associated with the  -Z.   If  the
                     base64  string  assigned results in more data, it will be
                     truncated.  Otherwise, it will be filled with bytes whose
                     value  is zero.  The printf format %B can be used to out-
                     put the actual data in this buffer instead of the  base64
                     encoding of the data.
              -i     Declares  vname  to be represented internally as integer.
                     The right hand side of an assignment is evaluated  as  an
                     arithmetic expression when assigning to an integer.  If n
                     is non-zero, it defines the output arithmetic base,  oth-
                     erwise the output base will be ten.
              -l     All  upper-case  characters  are converted to lower-case.
                     The upper-case option, -u, is turned off.
              -n     Declares vname to be a reference to  the  variable  whose
                     name  is defined by the value of variable vname.  This is
                     usually used to reference a variable  inside  a  function
                     whose name has been passed as an argument.
              -r     The given vnames are marked readonly and these names can-
                     not be changed by subsequent assignment.
              -t     Tags the variables.  Tags are user definable and have  no
                     special meaning to the shell.
              -u     All  lower-case  characters  are converted to upper-case.
                     The lower-case option, -l, is turned off.
              -x     The given vnames are marked for automatic export  to  the
                     environment of subsequently-executed commands.  Variables
                     whose names contain a .  cannot be exported.

              The -i attribute cannot be specified along with -R, -L,  -Z,  or
              -f.

              Using + rather than - causes these options to be turned off.  If
              no vname arguments are given, a list of vnames  (and  optionally
              the values) of the variables is printed.  (Using + rather than -
              keeps the values from being  printed.)   The  -p  option  causes
              typeset followed by the option letters to be printed before each
              name rather than the names of the options.  If any option  other
              than  -p  is  given,  only those variables which have all of the
              given options are printed.  Otherwise, the vnames and attributes
              of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
              Set  or display a resource limit.  The available resource limits
              are listed below.  Many systems do not support one  or  more  of
              these  limits.   The  limit for a specified resource is set when
              limit is specified.  The value of limit can be a number  in  the
              unit specified below with each resource, or the value unlimited.
              The -H and -S options specify whether the hard limit or the soft
              limit  for  the  given  resource is set.  A hard limit cannot be
              increased once it is set.  A soft limit can be increased  up  to
              the  value of the hard limit.  If neither the H nor S options is
              specified, the limit applies  to  both.   The  current  resource
              limit  is printed when limit is omitted.  In this case, the soft
              limit is printed unless H is  specified.   When  more  than  one
              resource  is  specified, then the limit name and unit is printed
              before the value.
              -a     Lists all of the current resource limits.
              -c     The number of 512-byte blocks on the size of core  dumps.
              -d     The number of K-bytes on the size of the data area.
              -f     The  number of 512-byte blocks on files that can be writ-
                     ten by the current process or by child  processes  (files
                     of any size may be read).
              -m     The number of K-bytes on the size of physical memory.
              -n     The number of file descriptors plus 1.
              -p     The number of 512-byte blocks for pipe buffering.
              -s     The number of K-bytes on the size of the stack area.
              -t     The number of CPU seconds to be used by each process.
              -v     The number of K-bytes for virtual memory.

              If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
              The user file-creation mask is set to mask (see umask(2)).  mask
              can either be an octal number or a symbolic value  as  described
              in  chmod(1).  If a symbolic value is given, the new umask value
              is the complement of the result of applying mask to the  comple-
              ment  of the previous umask value.  If mask is omitted, the cur-
              rent value of the mask is printed.  The  -S  option  causes  the
              mode  to be printed as a symbolic value.  Otherwise, the mask is
              printed in octal.

       † unalias [ -a ] name ...
              The aliases given by the list of  names  are  removed  from  the
              alias list.  The -a option causes all the aliases to be unset.

       †unset [ -fnv ] vname ...
              The  variables given by the list of vnames are unassigned, i.e.,
              their values and attributes are erased.  Readonly variables can-
              not  be unset.  If the -f option is set, then the names refer to
              function names.  If the -v option is set, then the  names  refer
              to  variable  names.   The -f option overrides -v.  If -n is set
              and name is a name reference, then name  will  be  unset  rather
              than the variable that it references.  The default is equivalent
              to -v.  Unsetting LINENO,  MAILCHECK,  OPTARG,  OPTIND,  RANDOM,
              SECONDS, TMOUT, and _ removes their special meaning even if they
              are subsequently assigned to.

       wait [ job ... ]
              Wait for the specified job and report  its  termination  status.
              If  job  is not given, then all currently active child processes
              are waited for.  The exit status from this command  is  that  of
              the last process waited for if job is specified; otherwise it is
              zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
              For each name, indicate how it would be interpreted if used as a
              command name.
              The  -v  option  produces a more verbose report.  The -f options
              skips the search for functions.   The  -p  option  does  a  path
              search  for  name  even  if  name  is an alias, a function, or a
              reserved word.  The -a option is similar to the  -v  option  but
              causes all interpretations of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero ($0) is -, then the shell is assumed to be a login shell and  com-
       mands  are  read from /etc/profile and then from either .profile in the
       current directory or $HOME/.profile, if either file exists.  Next,  for
       interactive shells, commands are read from the file named by performing
       parameter expansion, command substitution, and arithmetic  substitution
       on  the  value  of the environment variable ENV if the file exists.  If
       the -s option is not present and arg and a file  by  the  name  of  arg
       exits, then it reads and executes this script.  Otherwise, if the first
       arg does not contain a /, a path search is performed on the  first  arg
       to  determine  the  name of the script to execute.  The script arg must
       have execute permission and any setuid  and  setgid  settings  will  be
       ignored.   If  the script is not found on the path, arg is processed as
       if it named a built-in command or function.  Commands are then read  as
       described  below;  the  following  options are interpreted by the shell
       when it is invoked:

       -c        If the -c option is present, then commands are read from  the
                 first arg.  Any remaining arguments become positional parame-
                 ters starting at 0.
       -s        If the -s option is present or if no arguments  remain,  then
                 commands  are  read  from  the standard input.  Shell output,
                 except for the output of the Special Commands  listed  above,
                 is written to file descriptor 2.
       -i        If  the -i option is present or if the shell input and output
                 are attached to a terminal (as told  by  tcgetattr(2)),  then
                 this  shell is interactive.  In this case TERM is ignored (so
                 that kill 0 does not kill an interactive shell) and  INTR  is
                 caught  and  ignored (so that wait is interruptible).  In all
                 cases, QUIT is ignored by the shell.
       -r        If the -r option is present, the shell is a restricted shell.
       -D        A  list of all double quoted strings that are preceded by a $
                 will be printed on standard output and the shell  will  exit.
                 This  set  of strings will be subject to language translation
                 when the locale is not C or POSIX.  No commands will be  exe-
                 cuted.

       -P        If  -P or -o profile is present, the shell is a profile shell
                 (see pfexec(1)).

       -R filename
                 The -R filename option is used to generate a cross  reference
                 database that can be used by a separate utility to find defi-
                 nitions and references for variables and commands.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh  is  used  to  set up login names and execution environments whose
       capabilities are more controlled than those of the standard shell.  The
       actions  of rksh are identical to those of ksh, except that the follow-
       ing are disallowed:
              changing directory (see cd(1)),
              setting or unsetting the value  or  attributes  of  SHELL,  ENV,
              FPATH, or PATH,
              specifying path or command names containing /,
              redirecting output (>, >|, <>, and >>).
              adding or deleting built-in commands.
              using command -p to invoke a command.

       The  restrictions  above  are enforced after .profile and the ENV files
       are interpreted.

       When a command to be executed is found to be a  shell  procedure,  rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user shell procedures that have access to the full power of  the  stan-
       dard  shell,  while  imposing  a  limited menu of commands; this scheme
       assumes that the end-user does not have write and  execute  permissions
       in the same directory.

       The  net  effect  of these rules is that the writer of the .profile has
       complete control over user  actions,  by  performing  guaranteed  setup
       actions  and leaving the user in an appropriate directory (probably not
       the login directory).

       The system administrator often sets up a directory of  commands  (e.g.,
       /usr/rbin) that can be safely invoked by rksh.


EXIT STATUS

       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-interac-
       tively,  then execution of the shell file is abandoned unless the error
       occurs inside a subshell in which case the subshell is abandoned.  Oth-
       erwise,  the shell returns the exit status of the last command executed
       (see also the exit command above).  Run time  errors  detected  by  the
       shell  are  reported  by  printing the command or function name and the
       error condition.  If the line number that  the  error  occurred  on  is
       greater than one, then the line number is also printed in square brack-
       ets ([]) after the command or function name.


FILES

       /etc/passwd
       /etc/profile
       /etc/suid_profile
       $HOME/.profile
       /tmp/sh∗
       /dev/null


SEE ALSO

       cat(1), cd(1), chmod(1), cut(1), echo(1), emacs(1),  env(1),  gmacs(1),
       newgrp(1),   pfexec(1),  stty(1),  test(1),  umask(1),  vi(1),  dup(2),
       exec(2), fork(2), ioctl(2), lseek(2), paste(1),  pathconf(2),  pipe(2),
       sysconf(2),  umask(2),  ulimit(2),  wait(2),  rand(3),  a.out(5),  pro-
       file(5), environ(7).

       Morris I. Bolsky and David G. Korn, The New KornShell Command and  Pro-
       gramming Language, Prentice Hall, 1995.

       POSIX  -  Part  2:  Shell  and Utilities, IEEE Std 1003.2-1992, ISO/IEC
       9945-2, IEEE, 1993.


CAVEATS

       If a command is executed, and then a command  with  the  same  name  is
       installed  in a directory in the search path before the directory where
       the original command was found, the shell will  continue  to  exec  the
       original  command.   Use  the -t option of the alias command to correct
       this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe char-
       acter .

       Using  the  hist  built-in command within a compound command will cause
       the whole command to disappear from the history file.

       The built-in command . file reads the whole file  before  any  commands
       are  executed.   Therefore, alias and unalias commands in the file will
       not apply to any commands defined in the file.

       Traps are not processed while a job is waiting for  a  foreground  pro-
       cess.   Thus, a trap on CHLD won’t be executed until the foreground job
       terminates.

       It is a good idea to leave a space after the comma operator  in  arith-
       metic  expressions  to  prevent the comma from being interpreted as the
       decimal point character in certain locales.



RDS Standard              User Environment Utilities                    KSH(1)

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