getopt



GETOPT(1)                                                            GETOPT(1)




NAME

       getopt - parse command options (enhanced)


SYNOPSIS

       getopt optstring parameters

       getopt [options] [--] optstring parameters

       getopt [options] -o|--options optstring [options] [--] parameters


DESCRIPTION

       getopt  is  used  to break up (parse) options in command lines for easy
       parsing by shell procedures, and to check for legal options.   It  uses
       the GNU getopt(3) routines to do this.

       The  parameters  getopt  is  called with can be divided into two parts:
       options  which  modify  the  way  getopt  will   parse   (options   and
       -o|--options  optstring  in the SYNOPSIS), and the parameters which are
       to be parsed (parameters in the SYNOPSIS).  The second part will  start
       at  the  first  non-option parameter that is not an option argument, or
       after the first occurrence of ‘--’.  If no ‘-o’ or  ‘--options’  option
       is  found  in the first part, the first parameter of the second part is
       used as the short options string.

       If the environment variable GETOPT_COMPATIBLE is set, or if  its  first
       parameter  is  not  an  option  (does not start with a ‘-’, this is the
       first format in the SYNOPSIS), getopt will generate output that is com-
       patible  with  that  of  other versions of getopt(1).  It will still do
       parameter shuffling and recognize optional arguments (see section  COM-
       PATIBILITY for more information).

       Traditional  implementations  of  getopt(1)  are  unable  to  cope with
       whitespace and other (shell-specific) special characters  in  arguments
       and  non-option  parameters. To solve this problem, this implementation
       can generate quoted output which must once again be interpreted by  the
       shell  (usually by using the eval command). This has the effect of pre-
       serving those characters, but you must call getopt in a way that is  no
       longer  compatible  with  other versions (the second or third format in
       the SYNOPSIS).  To determine whether this enhanced version of getopt(1)
       is installed, a special test option (-T) can be used.


OPTIONS

       -a, --alternative
              Allow long options to start with a single ‘-’.

       -h, --help
              Output a small usage guide and exit succesfully. No other output
              is generated.

       -l, --longoptions longopts
              The long (multi-character) options to be recognized.  More  than
              one  option  name  may  be  specified at once, by separating the
              names with commas. This option may be given more than once,  the
              longopts  are cumulative.  Each long option name in longopts may
              be followed by one colon to indicate it  has  a  required  argu-
              ment,and  by two colons to indicate it has an optional argument.

       -n, --name progname
              The name that will be used by the  getopt(3)  routines  when  it
              reports errors. Note that errors of getopt(1) are still reported
              as coming from getopt.

       -o, --options shortopts
              The short (one-character) options  to  be  recognized.  If  this
              option is not found, the first parameter of getopt that does not
              start with a ‘-’ (and is not an option argument) is used as  the
              short  options string.  Each short option character in shortopts
              may be followed by one colon to indicate it has a required argu-
              ment, and by two colons to indicate it has an optional argument.
              The first character of shortopts may be ‘+’ or ‘-’ to  influence
              the  way options are parsed and output is generated (see section
              SCANNING MODES for details).

       -q, --quiet
              Disable error reporting by getopt(3).

       -Q, --quiet-output
              Do not generate normal output.  Errors  are  still  reported  by
              getopt(3), unless you also use -q.

       -s, --shell shell
              Set  quoting conventions to those of shell. If no -s argument is
              found, the BASH conventions are used. Valid arguments  are  cur-
              rently ‘sh’ ‘bash’, ‘csh’, and ‘tcsh’.

       -u, --unquoted
              Do  not  quote  the  output.  Note  that  whitespace and special
              (shell-dependent) characters can cause havoc in this mode  (like
              they do with other getopt(1) implementations).

       -T --test
              Test  if  your getopt(1) is this enhanced version or an old ver-
              sion. This generates no output, and sets the error status to  4.
              Other  implementations  of  getopt(1),  and  this version if the
              environment variable GETOPT_COMPATIBLE is set, will return  ‘--’
              and error status 0.

       -V, --version
              Output version information and exit succesfully. No other output
              is generated.


PARSING

       This section specifies the format of the second part of the  parameters
       of  getopt (the parameters in the SYNOPSIS).  The next section (OUTPUT)
       describes the output that is generated. These parameters were typically
       the  parameters  a  shell function was called with.  Care must be taken
       that each parameter the shell function was called with  corresponds  to
       exactly  one  parameter  in the parameter list of getopt (see the EXAM-
       PLES).  All parsing is done by the GNU getopt(3) routines.

       The parameters are parsed from left to right. Each parameter is classi-
       fied  as  a short option, a long option, an argument to an option, or a
       non-option parameter.

       A simple short option is a ‘-’ followed by a short option character. If
       the  option  has  a required argument, it may be written directly after
       the option character or as the next parameter (ie. separated by whites-
       pace  on  the command line). If the option has an optional argument, it
       must be written directly after the option character if present.

       It is possible to specify several short options after one ‘-’, as  long
       as  all  (except  possibly  the  last) do not have required or optional
       arguments.

       A long option normally begins with ‘--’ followed  by  the  long  option
       name.   If  the  option  has  a  required  argument,  it may be written
       directly after the long option name, separated by ‘=’, or as  the  next
       argument  (ie.  separated  by  whitespace on the command line).  If the
       option has an optional argument, it must be written directly after  the
       long  option name, separated by ‘=’, if present (if you add the ‘=’ but
       nothing behind it, it is interpreted as if  no  argument  was  present;
       this  is a slight bug, see the BUGS).  Long options may be abbreviated,
       as long as the abbreviation is not ambiguous.

       Each parameter not starting with a ‘-’, and not a required argument  of
       a  previous  option,  is a non-option parameter. Each parameter after a
       ‘--’ parameter is always interpreted as a non-option parameter.  If the
       environment  variable  POSIXLY_CORRECT  is  set, or if the short option
       string started with a ‘+’, all remaining parameters are interpreted  as
       non-option  parameters  as  soon  as  the first non-option parameter is
       found.


OUTPUT

       Output is generated for each element described in the previous section.
       Output  is  done in the same order as the elements are specified in the
       input, except for non-option parameters. Output can be done in compati-
       ble  (unquoted)  mode, or in such way that whitespace and other special
       characters within arguments and  non-option  parameters  are  preserved
       (see  QUOTING).   When  the output is processed in the shell script, it
       will seem to be composed of distinct elements that can be processed one
       by  one  (by  using the shift command in most shell languages). This is
       imperfect in unquoted mode, as elements  can  be  split  at  unexpected
       places if they contain whitespace or special characters.

       If  there  are  problems  parsing the parameters, for example because a
       required argument is not found or an option is not recognized, an error
       will  be  reported on stderr, there will be no output for the offending
       element, and a non-zero error status is returned.

       For a short option, a single ‘-’ and the option character are generated
       as  one  parameter.  If  the option has an argument, the next parameter
       will be the argument. If the option takes  an  optional  argument,  but
       none  was  found,  the next parameter will be generated but be empty in
       quoting mode, but no second parameter will  be  generated  in  unquoted
       (compatible)  mode.   Note  that many other getopt(1) implemetations do
       not support optional arguments.

       If several short options were specified after a single ‘-’,  each  will
       be present in the output as a separate parameter.

       For  a  long option, ‘--’ and the full option name are generated as one
       parameter. This is done regardless whether the option  was  abbreviated
       or  specified  with a single ‘-’ in the input. Arguments are handled as
       with short options.

       Normally, no  non-option  parameters  output  is  generated  until  all
       options and their arguments have been generated. Then ‘--’ is generated
       as a single parameter, and after it the non-option  parameters  in  the
       order they were found, each as a separate parameter.  Only if the first
       character of the short options string was a ‘-’,  non-option  parameter
       output  is  generated at the place they are found in the input (this is
       not supported if the first format of the SYNOPSIS is used; in that case
       all preceding occurrences of ‘-’ and ‘+’ are ignored).


QUOTING

       In  compatible mode, whitespace or ’special’ characters in arguments or
       non-option parameters are not handled correctly. As the output  is  fed
       to  the  shell  script,  the script does not know how it is supposed to
       break the output into separate parameters.  To circumvent this problem,
       this  implementation  offers quoting. The idea is that output is gener-
       ated with quotes around each parameter. When this output is once  again
       fed  to  the  shell (usually by a shell eval command), it is split cor-
       rectly into separate parameters.

       Quoting is not enabled if the environment variable GETOPT_COMPATIBLE is
       set,  if  the first form of the SYNOPSIS is used, or if the option ‘-u’
       is found.

       Different shells use different quoting conventions.  You  can  use  the
       ‘-s’ option to select the shell you are using. The following shells are
       currently supported: ‘sh’, ‘bash’, ‘csh’ and  ‘tcsh’.   Actually,  only
       two  ‘flavors’  are  distinguished:  sh-like  quoting  conventions  and
       csh-like quoting conventions. Chances are that if you use another shell
       script language, one of these flavors can still be used.



SCANNING MODES

       The  first  character of the short options string may be a ‘-’ or a ‘+’
       to indicate a special scanning mode. If the first calling form  in  the
       SYNOPSIS   is   used   they   are  ignored;  the  environment  variable
       POSIXLY_CORRECT is still examined, though.

       If  the  first  character  is  ‘+’,  or  if  the  environment  variable
       POSIXLY_CORRECT  is  set, parsing stops as soon as the first non-option
       parameter (ie. a parameter that does not start with  a  ‘-’)  is  found
       that is not an option argument. The remaining parameters are all inter-
       preted as non-option parameters.

       If the first character is a ‘-’, non-option parameters are outputed  at
       the  place where they are found; in normal operation, they are all col-
       lected at the end of output after a ‘--’ parameter has been  generated.
       Note that this ‘--’ parameter is still generated, but it will always be
       the last parameter in this mode.


COMPATIBILITY

       This version of getopt(1) is written to be as compatible as possible to
       other  versions.  Usually  you  can just replace them with this version
       without any modifications, and with some advantages.

       If the first character of the first parameter of getopt is not  a  ‘-’,
       getopt goes into compatibility mode. It will interpret its first param-
       eter as the string of short options, and all other  arguments  will  be
       parsed. It will still do parameter shuffling (ie. all non-option param-
       eters are  outputed  at  the  end),  unless  the  environment  variable
       POSIXLY_CORRECT is set.

       The  environment variable GETOPT_COMPATIBLE forces getopt into compati-
       bility mode. Setting both this environment variable and POSIXLY_CORRECT
       offers  100%  compatibility  for ‘difficult’ programs. Usually, though,
       neither is needed.

       In compatibility mode, leading ‘-’ and  ‘+’  characters  in  the  short
       options string are ignored.


RETURN CODES

       getopt  returns  error  code  0  for  succesful parsing, 1 if getopt(3)
       returns errors, 2 if it does not understand its own parameters, 3 if an
       internal  error  occurs  like out-of-memory, and 4 if it is called with
       -T.


EXAMPLES

       Example scripts for (ba)sh and (t)csh are provided with  the  getopt(1)
       distribution,  and are optionally installed in /usr/local/lib/getopt or
       /usr/lib/getopt.


ENVIRONMENT

       POSIXLY_CORRECT
              This environment variable is examined by the getopt(3) routines.
              If it is set, parsing stops as soon as a parameter is found that
              is not an option or an option argument. All remaining parameters
              are   also  interpreted  as  non-option  parameters,  regardless
              whether they start with a ‘-’.

       GETOPT_COMPATIBLE
              Forces getopt to use the first calling format  as  specified  in
              the SYNOPSIS.


BUGS

       getopt(3) can parse long options with optional arguments that are given
       an empty optional argument (but can not do  this  for  short  options).
       This getopt(1) treats optional arguments that are empty as if they were
       not present.

       The syntax if you do not want any short option variables at all is  not
       very  intuitive (you have to set them explicitely to the empty string).



AUTHOR

       Frodo Looijaard <frodol@dds.nl>


SEE ALSO

       getopt(3), bash(1), tcsh(1).




Linux                            May 31, 1997                        GETOPT(1)

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