expect



EXPECT(1)                                                            EXPECT(1)




NAME

       expect - programmed dialogue with interactive programs, Version 5


SYNOPSIS

       expect [ -dDinN ] [ -c cmds ] [ [ -[f|b] ] cmdfile ] [ args ]


INTRODUCTION

       Expect  is a program that "talks" to other interactive programs accord-
       ing to a script.  Following  the  script,  Expect  knows  what  can  be
       expected  from  a  program and what the correct response should be.  An
       interpreted language provides branching and high-level  control  struc-
       tures  to  direct the dialogue.  In addition, the user can take control
       and interact directly when desired, afterward returning control to  the
       script.

       Expectk is a mixture of Expect and Tk.  It behaves just like Expect and
       Tk’s wish.  Expect can also be used directly in  C  or  C++  (that  is,
       without Tcl).  See libexpect(3).

       The name "Expect" comes from the idea of send/expect sequences popular-
       ized by uucp, kermit and other modem control programs.  However  unlike
       uucp,  Expect is generalized so that it can be run as a user-level com-
       mand with any program and task in mind.  Expect can  actually  talk  to
       several programs at the same time.

       For example, here are some things Expect can do:

              ·   Cause  your computer to dial you back, so that you can login
                  without paying for the call.

              ·   Start a game (e.g., rogue) and if the optimal  configuration
                  doesn’t  appear, restart it (again and again) until it does,
                  then hand over control to you.

              ·   Run fsck, and in response to its  questions,  answer  "yes",
                  "no"  or  give  control  back to you, based on predetermined
                  criteria.

              ·   Connect to another network or  BBS  (e.g.,  MCI  Mail,  Com-
                  puServe)  and  automatically  retrieve  your mail so that it
                  appears as if it was originally sent to your local system.

              ·   Carry environment variables, current directory, or any  kind
                  of information across rlogin, telnet, tip, su, chgrp, etc.

       There  are  a  variety  of  reasons  why the shell cannot perform these
       tasks.  (Try, you’ll see.)  All are possible with Expect.

       In general, Expect is useful for running  any  program  which  requires
       interaction between the program and the user.  All that is necessary is
       that the interaction can be characterized programmatically.  Expect can
       also give the user back control (without halting the program being con-
       trolled) if desired.  Similarly, the user can  return  control  to  the
       script at any time.


USAGE

       Expect  reads  cmdfile  for  a list of commands to execute.  Expect may
       also be invoked implicitly on systems which support the #! notation  by
       marking  the  script  executable,  and  making  the  first line in your
       script:

           #!/usr/local/bin/expect -f

       Of course, the  path  must  accurately  describe  where  Expect  lives.
       /usr/local/bin is just an example.

       The -c flag prefaces a command to be executed before any in the script.
       The command should be quoted to prevent being broken up by  the  shell.
       This  option may be used multiple times.  Multiple commands may be exe-
       cuted with a single -c by separating them  with  semicolons.   Commands
       are  executed  in  the  order  they  appear.  (When using Expectk, this
       option is specified as -command.)

       The -d flag enables some diagnostic  output,  which  primarily  reports
       internal  activity  of commands such as expect and interact.  This flag
       has the same effect as "exp_internal 1" at the beginning of  an  Expect
       script,  plus the version of Expect is printed.  (The strace command is
       useful for tracing statements, and the  trace  command  is  useful  for
       tracing  variable  assignments.)   (When  using Expectk, this option is
       specified as -diag.)

       The -D flag enables an interactive debugger.  An integer  value  should
       follow.   The  debugger will take control before the next Tcl procedure
       if the value is non-zero or if a ^C is pressed (or a breakpoint is hit,
       or  other appropriate debugger command appears in the script).  See the
       README file or SEE ALSO (below) for more information on  the  debugger.
       (When using Expectk, this option is specified as -Debug.)

       The -f flag prefaces a file from which to read commands from.  The flag
       itself is optional as it is only useful when using the #! notation (see
       above),  so  that  other arguments may be supplied on the command line.
       (When using Expectk, this option is specified as -file.)

       By default, the command file is read into memory and  executed  in  its
       entirety.   It  is  occasionally  desirable to read files one line at a
       time.  For example, stdin is read this way.  In order  to  force  arbi-
       trary  files  to  be  handled  this  way, use the -b flag.  (When using
       Expectk, this option is specified as  -buffer.)Notethatstdio-buffering-
       maystilltakeplacehoweverthisshouldn’tcauseproblemswhenreadingfromafi-
       foorstdin.

       If the string "-" is supplied as a filename,  standard  input  is  read
       instead.  (Use "./-" to read from a file actually named "-".)

       The  -i flag causes Expect to interactively prompt for commands instead
       of reading them from a file.  Prompting is terminated via the exit com-
       mand or upon EOF.  See interpreter (below) for more information.  -i is
       assumed if neither a command file nor -c is used.  (When using Expectk,
       this option is specified as -interactive.)

       --  may  be  used to delimit the end of the options.  This is useful if
       you want to pass an option-like argument  to  your  script  without  it
       being  interpreted  by  Expect.   This can usefully be placed in the #!
       line to prevent any flag-like interpretation by Expect.   For  example,
       the  following  will leave the original arguments (including the script
       name) in the variable argv.

           #!/usr/local/bin/expect --

       Note that  the  usual  getopt(3)  and  execve(2)  conventions  must  be
       observed when adding arguments to the #! line.

       The  file  $exp_library/expect.rc  is sourced automatically if present,
       unless the -N flag is used.  (When using Expectk, this option is speci-
       fied  as  -NORC.)   Immediately  after  this,  the file ~/.expect.rc is
       sourced automatically, unless the -n flag is used.  If the  environment
       variable DOTDIR is defined, it is treated as a directory and .expect.rc
       is read from there.  (When using Expectk, this option is  specified  as
       -norc.)  This sourcing occurs only after executing any -c flags.

       -v  causes  Expect  to  print its version number and exit.  (The corre-
       sponding flag in Expectk, which uses long flag names, is -version.)

       Optional args are constructed into a list and stored  in  the  variable
       named argv.  argc is initialized to the length of argv.

       argv0  is  defined to be the name of the script (or binary if no script
       is used).  For example, the following prints out the name of the script
       and the first three arguments:

           send_user "$argv0 [lrange $argv 0 2]\n"



COMMANDS

       Expect  uses  Tcl  (Tool  Command Language).  Tcl provides control flow
       (e.g., if, for, break), expression evaluation and  several  other  fea-
       tures such as recursion, procedure definition, etc.  Commands used here
       but not defined (e.g., set, if, exec) are Tcl  commands  (see  tcl(3)).
       Expect supports additional commands, described below.  Unless otherwise
       specified, commands return the empty string.

       Commands are listed alphabetically so that they can be quickly located.
       However,  new users may find it easier to start by reading the descrip-
       tions of spawn, send, expect, and interact, in that order.

       Note that the best introduction to the language (both Expect  and  Tcl)
       is provided in the book "Exploring Expect" (see SEE ALSO below).  Exam-
       ples are included in this man page but they are very limited since this
       man page is meant primarily as reference material.

       Note  that in the text of this man page, "Expect" with an uppercase "E"
       refers to the Expect program  while  "expect"  with  a  lower-case  "e"
       refers to the expect command within the Expect program.)

       close [-slave] [-onexec 0|1] [-i spawn_id]
             closes  the  connection to the current process.  Most interactive
             programs will detect EOF on their stdin and exit; thus close usu-
             ally  suffices to kill the process as well.  The -i flag declares
             the process to close corresponding to the named spawn_id.

             Both expect and interact will detect  when  the  current  process
             exits and implicitly do a close.  But if you kill the process by,
             say, "exec kill $pid", you will need to explicitly call close.

             The -onexec flag determines whether the spawn id will  be  closed
             in  any new spawned processes or if the process is overlayed.  To
             leave a spawn id open, use the value 0.  A non-zero integer value
             will force the spawn closed (the default) in any new processes.

             The  -slave  flag  closes the slave associated with the spawn id.
             (See "spawn -pty".)  When the connection is closed, the slave  is
             automatically closed as well if still open.

             No  matter whether the connection is closed implicitly or explic-
             itly, you should call wait to clear up the  corresponding  kernel
             process slot.  close does not call wait since there is no guaran-
             tee that closing a process connection will cause it to exit.  See
             wait below for more info.

       debug [[-now] 0|1]
             controls  a Tcl debugger allowing you to step through statements,
             set breakpoints, etc.

             With no arguments, a  1  is  returned  if  the  debugger  is  not
             running, otherwise a 0 is returned.

             With  a  1 argument, the debugger is started.  With a 0 argument,
             the debugger is stopped.  If a 1 argument is preceded by the -now
             flag, the debugger is started immediately (i.e., in the middle of
             the debug command itself).  Otherwise, the  debugger  is  started
             with the next Tcl statement.

             The  debug  command  does  not change any traps.  Compare this to
             starting Expect with the -D flag (see above).

             See the README file or SEE ALSO (below) for more  information  on
             the debugger.

       disconnect
             disconnects  a  forked  process  from the terminal.  It continues
             running in the background.  The process is given its own  process
             group (if possible).  Standard I/O is redirected to /dev/null.

             The  following  fragment  uses disconnect to continue running the
             script in the background.

                 if {[fork]!=0} exit
                 disconnect
                 . . .

             The following script reads a password, and then  runs  a  program
             every  hour  that  demands  a  password each time it is run.  The
             script supplies the password so that you only  have  to  type  it
             once.   (See  the stty command which demonstrates how to turn off
             password echoing.)

                 send_user "password?\ "
                 expect_user -re "(.*)\n"
                 for {} 1 {} {
                     if {[fork]!=0} {sleep 3600;continue}
                     disconnect
                     spawn priv_prog
                     expect Password:
                     send "$expect_out(1,string)\r"
                     . . .
                     exit
                 }

             An advantage to using disconnect over the shell asynchronous pro-
             cess  feature (&) is that Expect can save the terminal parameters
             prior to disconnection, and then later apply them  to  new  ptys.
             With  &,  Expect  does  not  have a chance to read the terminal’s
             parameters since the terminal is already disconnected by the time
             Expect receives control.

       exit [-opts] [status]
             causes Expect to exit or otherwise prepare to do so.

             The  -onexit  flag causes the next argument to be used as an exit
             handler.  Without  an  argument,  the  current  exit  handler  is
             returned.

             The  -noexit flag causes Expect to prepare to exit but stop short
             of actually returning control to the operating system.  The user-
             defined exit handler is run as well as Expect’s own internal han-
             dlers.  No further Expect commands should be executed.   This  is
             useful  if you are running Expect with other Tcl extensions.  The
             current interpreter (and main window if in  the  Tk  environment)
             remain  so  that  other Tcl extensions can clean up.  If Expect’s
             exit is called again (however this might occur), the handlers are
             not rerun.

             Upon  exiting,  all  connections to spawned processes are closed.
             Closure will be detected as an EOF by  spawned  processes.   exit
             takes  no other actions beyond what the normal _exit(2) procedure
             does.  Thus, spawned processes that do not check for EOF may con-
             tinue  to  run.  (A variety of conditions are important to deter-
             mining, for example, what signals a spawned process will be sent,
             but   these  are  system-dependent,  typically  documented  under
             exit(3).)  Spawned processes that continue to run will be  inher-
             ited by init.

             status  (or 0 if not specified) is returned as the exit status of
             Expect.  exit is implicitly executed if the end of the script  is
             reached.

       exp_continue [-continue_timer]
             The command exp_continue allows expect itself to continue execut-
             ing rather than  returning  as  it  normally  would.  By  default
             exp_continue  resets  the timeout timer. The -continue_timer flag
             prevents timer from being restarted. (See expect for more  infor-
             mation.)

       exp_internal [-f file] value
             causes  further  commands to send diagnostic information internal
             to Expect to stderr if value is non-zero.  This  output  is  dis-
             abled  if  value is 0.  The diagnostic information includes every
             character received, and every attempt made to match  the  current
             output against the patterns.

             If the optional file is supplied, all normal and debugging output
             is written to that file (regardless of the value of value).   Any
             previous diagnostic output file is closed.

             The -info flag causes exp_internal to return a description of the
             most recent non-info arguments given.

       exp_open [args] [-i spawn_id]
             returns a Tcl file identifier that corresponds  to  the  original
             spawn  id.   The  file  identifier can then be used as if it were
             opened by Tcl’s open command.  (The spawn id should no longer  be
             used.  A wait should not be executed.

             The  -leaveopen  flag leaves the spawn id open for access through
             Expect commands.  A wait must be executed on the spawn id.

       exp_pid [-i spawn_id]
             returns the process id corresponding  to  the  currently  spawned
             process.  If the -i flag is used, the pid returned corresponds to
             that of the given spawn id.

       exp_send
             is an alias for send.

       exp_send_error
             is an alias for send_error.

       exp_send_log
             is an alias for send_log.

       exp_send_tty
             is an alias for send_tty.

       exp_send_user
             is an alias for send_user.

       exp_version [[-exit] version]
             is useful for assuring that the script  is  compatible  with  the
             current version of Expect.

             With  no  arguments,  the  current version of Expect is returned.
             This version may then be encoded in your script.  If you actually
             know  that you are not using features of recent versions, you can
             specify an earlier version.

             Versions consist of three numbers separated by  dots.   First  is
             the  major number.  Scripts written for versions of Expect with a
             different major number will almost certainly not work.   exp_ver-
             sion returns an error if the major numbers do not match.

             Second is the minor number.  Scripts written for a version with a
             greater minor number than the current  version  may  depend  upon
             some new feature and might not run.  exp_version returns an error
             if the major numbers  match,  but  the  script  minor  number  is
             greater than that of the running Expect.

             Third  is  a number that plays no part in the version comparison.
             However, it is incremented when the Expect software  distribution
             is  changed  in  any  way, such as by additional documentation or
             optimization.  It is reset to 0 upon each new minor version.

             With the -exit flag, Expect prints an error and exits if the ver-
             sion is out of date.

       expect [[-opts] pat1 body1] ... [-opts] patn [bodyn]
             waits  until  one of the patterns matches the output of a spawned
             process, a specified time period has passed, or an end-of-file is
             seen.  If the final body is empty, it may be omitted.

             Patterns  from  the most recent expect_before command are implic-
             itly used before any other  patterns.   Patterns  from  the  most
             recent  expect_after  command are implicitly used after any other
             patterns.

             If the arguments to the entire expect statement require more than
             one  line,  all  the  arguments may be "braced" into one so as to
             avoid terminating each line with a backslash.  In this one  case,
             the usual Tcl substitutions will occur despite the braces.

             If  a  pattern is the keyword eof, the corresponding body is exe-
             cuted upon end-of-file.  If a pattern is the keyword timeout, the
             corresponding  body is executed upon timeout.  If no timeout key-
             word is used, an implicit null action is executed  upon  timeout.
             The  default  timeout  period  is  10 seconds but may be set, for
             example to 30, by the command  "set  timeout  30".   An  infinite
             timeout  may  be designated by the value -1.  If a pattern is the
             keyword default, the corresponding body is executed  upon  either
             timeout or end-of-file.

             If  a  pattern  matches, then the corresponding body is executed.
             expect returns the result of the body (or the empty string if  no
             pattern matched).  In the event that multiple patterns match, the
             one appearing first is used to select a body.

             Each time new output arrives, it is compared to each  pattern  in
             the  order  they are listed.  Thus, you may test for absence of a
             match by making the last pattern something guaranteed to  appear,
             such  as  a  prompt.  In situations where there is no prompt, you
             must use timeout (just like you would  if  you  were  interacting
             manually).

             Patterns  are  specified in three ways.  By default, patterns are
             specified as with Tcl’s string match command.  (Such patterns are
             also  similar  to C-shell regular expressions usually referred to
             as "glob" patterns).  The -gl flag may may  be  used  to  protect
             patterns  that  might otherwise match expect flags from doing so.
             Any pattern beginning with a "-" should be  protected  this  way.
             (All  strings starting with "-" are reserved for future options.)


             For example, the following fragment looks for a successful login.
             (Note  that abort is presumed to be a procedure defined elsewhere
             in the script.)

                 expect {
                     busy               {puts busy\n ; exp_continue}
                     failed             abort
                     "invalid password" abort
                     timeout            abort
                     connected
                 }

             Quotes are necessary on the fourth pattern since  it  contains  a
             space,  which  would  otherwise  separate  the  pattern  from the
             action.  Patterns with the same action (such as the 3rd and  4th)
             require  listing  the  actions again.  This can be avoid by using
             regexp-style patterns (see below).  More information  on  forming
             glob-style patterns can be found in the Tcl manual.

             Regexp-style  patterns  follow the syntax defined by Tcl’s regexp
             (short for "regular expression") command.   regexp  patterns  are
             introduced  with  the  flag  -re.   The  previous  example can be
             rewritten using a regexp as:

                 expect {
                     busy       {puts busy\n ; exp_continue}
                     -re "failed|invalid password" abort
                     timeout    abort
                     connected
                 }

             Both types of patterns are "unanchored".  This  means  that  pat-
             terns  do  not have to match the entire string, but can begin and
             end the match anywhere in the string (as long as everything  else
             matches).   Use  ^  to  match the beginning of a string, and $ to
             match the end.  Note that if you do not wait for  the  end  of  a
             string,  your  responses  can  easily end up in the middle of the
             string as they are echoed from the spawned process.  While  still
             producing  correct results, the output can look unnatural.  Thus,
             use of $ is encouraged if you can exactly describe the characters
             at the end of a string.

             Note  that  in  many editors, the ^ and $ match the beginning and
             end of lines respectively. However, because expect  is  not  line
             oriented,  these  characters  match  the beginning and end of the
             data (as opposed to  lines)  currently  in  the  expect  matching
             buffer.  (Also, see the note below on "system indigestion.")

             The  -ex  flag  causes  the  pattern  to be matched as an "exact"
             string.  No interpretation of *, ^, etc  is  made  (although  the
             usual  Tcl  conventions  must still be observed).  Exact patterns
             are always unanchored.


             The -nocase flag causes uppercase characters  of  the  output  to
             compare as if they were lowercase characters.  The pattern is not
             affected.

             While reading output, more than  2000  bytes  can  force  earlier
             bytes  to  be "forgotten".  This may be changed with the function
             match_max.  (Note that excessively large values can slow down the
             pattern  matcher.)   If patlist is full_buffer, the corresponding
             body is executed if match_max bytes have  been  received  and  no
             other patterns have matched.  Whether or not the full_buffer key-
             word  is  used,  the  forgotten   characters   are   written   to
             expect_out(buffer).

             If  patlist  is  the keyword null, and nulls are allowed (via the
             remove_nulls command), the corresponding body is  executed  if  a
             single  ASCII  0 is matched.  It is not possible to match 0 bytes
             via glob or regexp patterns.

             Upon matching a pattern (or eof or full_buffer), any matching and
             previously   unmatched   output   is   saved   in   the  variable
             expect_out(buffer).  Up to 9 regexp substring matches  are  saved
             in      the      variables      expect_out(1,string)      through
             expect_out(9,string).  If the -indices flag is used before a pat-
             tern,  the  starting  and  ending indices (in a form suitable for
             lrange)  of  the  10  strings  are  stored   in   the   variables
             expect_out(X,start)  and  expect_out(X,end)  where  X is a digit,
             corresponds to the substring position in the buffer.  0 refers to
             strings  which  matched  the  entire pattern and is generated for
             glob patterns as well as regexp patterns.  For example, if a pro-
             cess has produced output of "abcdefgh\n", the result of:

                 expect "cd"

             is as if the following statements had executed:

                 set expect_out(0,string) cd
                 set expect_out(buffer) abcd

             and "efgh\n" is left in the output buffer.  If a process produced
             the output "abbbcabkkkka\n", the result of:

                 expect -indices -re "b(b*).*(k+)"

             is as if the following statements had executed:

                 set expect_out(0,start) 1
                 set expect_out(0,end) 10
                 set expect_out(0,string) bbbcabkkkk
                 set expect_out(1,start) 2
                 set expect_out(1,end) 3
                 set expect_out(1,string) bb
                 set expect_out(2,start) 10
                 set expect_out(2,end) 10
                 set expect_out(2,string) k
                 set expect_out(buffer) abbbcabkkkk

             and "a\n" is left in the output buffer.  The pattern "*" (and -re
             ".*")  will flush the output buffer without reading any more out-
             put from the process.

             Normally, the matched output is discarded from Expect’s  internal
             buffers.   This  may be prevented by prefixing a pattern with the
             -notransfer flag.  This flag is especially useful in  experiment-
             ing  (and  can  be  abbreviated  to  "-not" for convenience while
             experimenting).

             The spawn id associated with  the  matching  output  (or  eof  or
             full_buffer) is stored in expect_out(spawn_id).

             The  -timeout  flag  causes the current expect command to use the
             following value as a timeout instead of using the  value  of  the
             timeout variable.

             By  default, patterns are matched against output from the current
             process, however the -i flag declares the output from  the  named
             spawn_id  list  be  matched against any following patterns (up to
             the next -i).  The spawn_id list should either  be  a  whitespace
             separated  list  of  spawn_ids  or a variable referring to such a
             list of spawn_ids.

             For example, the following example waits for "connected" from the
             current  process,  or "busy", "failed" or "invalid password" from
             the spawn_id named by $proc2.

                 expect {
                     -i $proc2 busy {puts busy\n ; exp_continue}
                     -re "failed|invalid password" abort
                     timeout abort
                     connected
                 }

             The value of the global variable  any_spawn_id  may  be  used  to
             match  patterns to any spawn_ids that are named with all other -i
             flags in the current expect command.  The spawn_id from a -i flag
             with no associated pattern (i.e., followed immediately by another
             -i) is made available to any other patterns in  the  same  expect
             command associated with any_spawn_id.

             The  -i  flag  may  also name a global variable in which case the
             variable is read for a list of spawn ids.  The variable is reread
             whenever  it  changes.   This  provides a way of changing the I/O
             source while the command is in  execution.   Spawn  ids  provided
             this way are called "indirect" spawn ids.

             Actions  such  as  break  and  continue  cause control structures
             (i.e., for, proc) to  behave  in  the  usual  way.   The  command
             exp_continue  allows  expect  itself to continue executing rather
             than returning as it normally would.

             This is useful for avoiding explicit  loops  or  repeated  expect
             statements.  The following example is part of a fragment to auto-
             mate rlogin.  The exp_continue avoids having to  write  a  second
             expect  statement  (to  look  for the prompt again) if the rlogin
             prompts for a password.

                 expect {
                     Password: {
                         stty -echo
                         send_user "password (for $user) on $host: "
                         expect_user -re "(.*)\n"
                         send_user "\n"
                         send "$expect_out(1,string)\r"
                         stty echo
                         exp_continue
                     } incorrect {
                         send_user "invalid password or account\n"
                         exit
                     } timeout {
                         send_user "connection to $host timed out\n"
                         exit
                     } eof {
                         send_user \
                             "connection to host failed: $expect_out(buffer)"
                         exit
                     } -re $prompt
                 }

             For example, the following fragment might help a  user  guide  an
             interaction that is already totally automated.  In this case, the
             terminal is put into raw  mode.   If  the  user  presses  "+",  a
             variable  is incremented.  If "p" is pressed, several returns are
             sent to the process, perhaps to poke it in some way, and "i" lets
             the  user  interact  with  the process, effectively stealing away
             control from the script.  In each case, the  exp_continue  allows
             the  current  expect to continue pattern matching after executing
             the current action.

                 stty raw -echo
                 expect_after {
                     -i $user_spawn_id
                     "p" {send "\r\r\r"; exp_continue}
                     "+" {incr foo; exp_continue}
                     "i" {interact; exp_continue}
                     "quit" exit
                 }


             By default, exp_continue resets the timeout timer.  The timer  is
             not restarted, if exp_continue is called with the -continue_timer
             flag.

       expect_after [expect_args]
             works identically to the expect_before except  that  if  patterns
             from  both  expect and expect_after can match, the expect pattern
             is used.  See the expect_before command for more information.

       expect_background [expect_args]
             takes the same arguments as expect, however  it  returns  immedi-
             ately.  Patterns are tested whenever new input arrives.  The pat-
             tern timeout and default are meaningless to expect_background and
             are silently discarded.  Otherwise, the expect_background command
             uses expect_before and expect_after  patterns  just  like  expect
             does.

             When  expect_background  actions  are being evaluated, background
             processing for the same spawn id is blocked.  Background process-
             ing  is  unblocked  when  the action completes.  While background
             processing is blocked, it is possible to do a (foreground) expect
             on the same spawn id.

             It  is  not  possible  to execute an expect while an expect_back-
             ground is unblocked.  expect_background for a particular spawn id
             is  deleted  by  declaring  a new expect_background with the same
             spawn id.  Declaring expect_background with  no  pattern  removes
             the  given  spawn  id  from  the ability to match patterns in the
             background.

       expect_before [expect_args]
             takes the same arguments as expect, however  it  returns  immedi-
             ately.   Pattern-action  pairs from the most recent expect_before
             with the same spawn id are  implicitly  added  to  any  following
             expect  commands.   If  a pattern matches, it is treated as if it
             had been specified in the expect command itself, and the  associ-
             ated  body  is executed in the context of the expect command.  If
             patterns from  both  expect_before  and  expect  can  match,  the
             expect_before pattern is used.

             If  no  pattern is specified, the spawn id is not checked for any
             patterns.

             Unless overridden by a  -i  flag,  expect_before  patterns  match
             against  the  spawn id defined at the time that the expect_before
             command was executed (not when its pattern is matched).

             The -info flag causes expect_before to return the current  speci-
             fications of what patterns it will match.  By default, it reports
             on the current spawn id.  An optional spawn id specification  may
             be given for information on that spawn id.  For example

                 expect_before -info -i $proc

             At most one spawn id specification may be given.  The flag -indi-
             rect suppresses direct spawn ids that  come  only  from  indirect
             specifications.

             Instead  of  a spawn id specification, the flag "-all" will cause
             "-info" to report on all spawn ids.

             The output of the -info flag can be reused  as  the  argument  to
             expect_before.

       expect_tty [expect_args]
             is  like  expect  but  it  reads  characters  from /dev/tty (i.e.
             keystrokes from the user).  By default, reading is  performed  in
             cooked  mode.   Thus,  lines  must end with a return in order for
             expect to see them.  This may be changed via stty (see  the  stty
             command below).

       expect_user [expect_args]
             is   like  expect  but  it  reads  characters  from  stdin  (i.e.
             keystrokes from the user).  By default, reading is  performed  in
             cooked  mode.   Thus,  lines  must end with a return in order for
             expect to see them.  This may be changed via stty (see  the  stty
             command below).

       fork  creates  a  new process.  The new process is an exact copy of the
             current Expect process.  On success, fork returns 0  to  the  new
             (child)  process  and returns the process ID of the child process
             to the parent process.  On failure (invariably  due  to  lack  of
             resources, e.g., swap space, memory), fork returns -1 to the par-
             ent process, and no child process is created.

             Forked processes exit via the exit command, just like the  origi-
             nal  process.   Forked  processes are allowed to write to the log
             files.  If you do not disable debugging or logging in most of the
             processes, the result can be confusing.

             Some  pty implementations may be confused by multiple readers and
             writers, even momentarily.  Thus, it is  safest  to  fork  before
             spawning processes.

       interact [string1 body1] ... [stringn [bodyn]]
             gives  control  of  the  current  process  to  the  user, so that
             keystrokes are sent to the current process, and  the  stdout  and
             stderr of the current process are returned.

             String-body  pairs  may  be specified as arguments, in which case
             the body is executed when the corresponding  string  is  entered.
             (By  default,  the  string  is  not sent to the current process.)
             The interpreter command is assumed, if the final body is missing.

             If  the  arguments  to the entire interact statement require more
             than one line, all the arguments may be "braced" into one  so  as
             to  avoid  terminating  each  line with a backslash.  In this one
             case, the usual Tcl substitutions will occur despite the  braces.

             For example, the following command runs interact with the follow-
             ing string-body pairs defined:  When ^Z  is  pressed,  Expect  is
             suspended.   (The -reset flag restores the terminal modes.)  When
             ^A is pressed, the user sees "you typed a control-A" and the pro-
             cess  is  sent  a ^A.  When $ is pressed, the user sees the date.
             When ^C is pressed, Expect exits.  If "foo" is entered, the  user
             sees  "bar".   When  ~~  is  pressed, the Expect interpreter runs
             interactively.

                 set CTRLZ \032
                 interact {
                     -reset $CTRLZ {exec kill -STOP [pid]}
                     \001   {send_user "you typed a control-A\n";
                             send "\001"
                            }
                     $      {send_user "The date is [exec date]."}
                     \003   exit
                     foo    {send_user "bar"}
                     ~~
                 }


             In string-body pairs, strings are matched in the order  they  are
             listed  as  arguments.  Strings that partially match are not sent
             to the current process in anticipation of the  remainder  coming.
             If characters are then entered such that there can no longer pos-
             sibly be a match, only the part of the string will be sent to the
             process  that cannot possibly begin another match.  Thus, strings
             that are substrings of partial matches can match  later,  if  the
             original  strings  that  was  attempting  to  be match ultimately
             fails.

             By default, string matching is exact with  no  wild  cards.   (In
             contrast,   the   expect  command  uses  glob-style  patterns  by
             default.)  The -ex flag may be  used  to  protect  patterns  that
             might  otherwise match interact flags from doing so.  Any pattern
             beginning with a  "-"  should  be  protected  this  way.     (All
             strings starting with "-" are reserved for future options.)

             The  -re  flag  forces  the string to be interpreted as a regexp-
             style pattern.  In this case, matching substrings are  stored  in
             the  variable interact_out similarly to the way expect stores its
             output in the variable expect_out.  The -indices  flag  is  simi-
             larly supported.

             The  pattern  eof introduces an action that is executed upon end-
             of-file.  A separate eof pattern may also follow the -output flag
             in  which  case it is matched if an eof is detected while writing
             output.  The default eof action is  "return",  so  that  interact
             simply returns upon any EOF.

             The  pattern timeout introduces a timeout (in seconds) and action
             that is executed after no characters have been read for  a  given
             time.  The timeout pattern applies to the most recently specified
             process.  There is no  default  timeout.   The  special  variable
             "timeout"  (used  by  the  expect  command) has no affect on this
             timeout.

             For example, the following statement could be used to  autologout
             users  who  have not typed anything for an hour but who still get
             frequent system messages:

                 interact -input $user_spawn_id timeout 3600 return -output \
                     $spawn_id


             If the pattern is the keyword null, and nulls  are  allowed  (via
             the  remove_nulls command), the corresponding body is executed if
             a single ASCII 0 is matched.  It is not possible to match 0 bytes
             via glob or regexp patterns.

             Prefacing  a  pattern  with  the flag -iwrite causes the variable
             interact_out(spawn_id) to be set to the  spawn_id  which  matched
             the pattern (or eof).

             Actions  such  as  break  and  continue  cause control structures
             (i.e., for, proc) to behave in the  usual  way.   However  return
             causes  interact  to  return  to  its  caller, while inter_return
             causes interact to cause a return in its caller.  For example, if
             "proc  foo"  called  interact  which  then  executed  the  action
             inter_return, proc foo would return.  (This means that if  inter-
             act  calls interpreter interactively typing return will cause the
             interact to continue, while inter_return will cause the  interact
             to return to its caller.)

             During  interact,  raw mode is used so that all characters may be
             passed to the current process.  If the current process  does  not
             catch job control signals, it will stop if sent a stop signal (by
             default ^Z).  To restart it, send a continue signal (such  as  by
             "kill  -CONT  <pid>").   If  you really want to send a SIGSTOP to
             such a process (by ^Z), consider spawning csh first and then run-
             ning  your  program.   On  the  other hand, if you want to send a
             SIGSTOP to Expect itself,  first  call  interpreter  (perhaps  by
             using an escape character), and then press ^Z.

             String-body  pairs can be used as a shorthand for avoiding having
             to enter the interpreter and execute commands interactively.  The
             previous  terminal  mode  is used while the body of a string-body
             pair is being executed.

             For speed, actions execute in raw mode by  default.   The  -reset
             flag  resets  the terminal to the mode it had before interact was
             executed (invariably, cooked mode).  Note that characters entered
             when  the mode is being switched may be lost (an unfortunate fea-
             ture of the terminal driver on some systems).  The only reason to
             use -reset is if your action depends on running in cooked mode.

             The  -echo flag sends characters that match the following pattern
             back to the process that generated  them  as  each  character  is
             read.   This  may  be  useful when the user needs to see feedback
             from partially typed patterns.

             If a pattern is being echoed but eventually fails to  match,  the
             characters  are sent to the spawned process.  If the spawned pro-
             cess then echoes them, the user will see  the  characters  twice.
             -echo  is  probably only appropriate in situations where the user
             is unlikely to not complete the pattern.  For example,  the  fol-
             lowing  excerpt is from rftp, the recursive-ftp script, where the
             user is prompted to enter ~g, ~p, or ~l, to get, put, or list the
             current  directory  recursively.   These are so far away from the
             normal ftp commands, that the user is unlikely to type ~ followed
             by anything else, except mistakenly, in which case, they’ll prob-
             ably just ignore the result anyway.

                 interact {
                     -echo ~g {getcurdirectory 1}
                     -echo ~l {getcurdirectory 0}
                     -echo ~p {putcurdirectory}
                 }

             The -nobuffer flag sends characters that match the following pat-
             tern on to the output process as characters are read.

             This  is useful when you wish to let a program echo back the pat-
             tern.  For example, the following might be used to monitor  where
             a  person  is  dialing (a Hayes-style modem).  Each time "atd" is
             seen the script logs the rest of the line.

                 proc lognumber {} {
                     interact -nobuffer -re "(.*)\r" return
                     puts $log "[exec date]: dialed $interact_out(1,string)"
                 }

                 interact -nobuffer "atd" lognumber


             During interact, previous use of log_user is ignored.  In partic-
             ular,  interact  will  force its output to be logged (sent to the
             standard output) since it is presumed the user  doesn’t  wish  to
             interact blindly.

             The  -o flag causes any following key-body pairs to be applied to
             the output of the current process.  This can be useful, for exam-
             ple, when dealing with hosts that send unwanted characters during
             a telnet session.

             By default, interact expects the user to  be  writing  stdin  and
             reading  stdout  of  the Expect process itself.  The -u flag (for
             "user") makes interact look for the user as the process named  by
             its argument (which must be a spawned id).

             This allows two unrelated processes to be joined together without
             using an explicit loop.  To aid in debugging, Expect  diagnostics
             always  go to stderr (or stdout for certain logging and debugging
             information).  For the same reason, the interpreter command  will
             read interactively from stdin.

             For  example,  the  following  fragment  creates a login process.
             Then it dials the user (not shown), and finally connects the  two
             together.   Of  course, any process may be substituted for login.
             A shell, for example, would allow the user to work  without  sup-
             plying an account and password.

                 spawn login
                 set login $spawn_id
                 spawn tip modem
                 # dial back out to user
                 # connect user to login
                 interact -u $login

             To  send  output  to  multiple processes, list each spawn id list
             prefaced by a -output flag.  Input for a group  of  output  spawn
             ids  may  be  determined  by a spawn id list prefaced by a -input
             flag.  (Both -input and -output may take lists in the  same  form
             as the -i flag in the expect command, except that any_spawn_id is
             not meaningful in interact.)  All following flags and strings (or
             patterns)  apply to this input until another -input flag appears.
             If no -input  appears,  -output  implies  "-input  $user_spawn_id
             -output".   (Similarly,  with  patterns that do not have -input.)
             If one -input is specified, it overrides  $user_spawn_id.   If  a
             second  -input  is specified, it overrides $spawn_id.  Additional
             -input flags may be specified.

             The two implied input processes default to having  their  outputs
             specified  as  $spawn_id  and  $user_spawn_id (in reverse).  If a
             -input flag appears with no -output flag,  characters  from  that
             process are discarded.

             The  -i  flag  introduces  a replacement for the current spawn_id
             when no other -input or  -output  flags  are  used.   A  -i  flag
             implies a -o flag.

             It  is possible to change the processes that are being interacted
             with by using  indirect  spawn  ids.   (Indirect  spawn  ids  are
             described  in the section on the expect command.)  Indirect spawn
             ids may be specified with the -i, -u, -input, or -output flags.

       interpreter  [args]
             causes the user to be interactively prompted for Expect  and  Tcl
             commands.  The result of each command is printed.

             Actions  such  as  break  and  continue  cause control structures
             (i.e., for, proc) to behave in the  usual  way.   However  return
             causes  interpreter  to  return to its caller, while inter_return
             causes interpreter to cause a return in its caller.  For example,
             if  "proc  foo" called interpreter which then executed the action
             inter_return, proc foo would return.  Any  other  command  causes
             interpreter to continue prompting for new commands.

             By  default, the prompt contains two integers.  The first integer
             describes the depth of the evaluation stack (i.e., how many times
             Tcl_Eval has been called).  The second integer is the Tcl history
             identifier.  The prompt can be set by defining a procedure called
             "prompt1"  whose  return  value  becomes  the  next prompt.  If a
             statement has open quotes, parens, braces, or  brackets,  a  sec-
             ondary  prompt  (by  default  "+> ") is issued upon newline.  The
             secondary prompt may  be  set  by  defining  a  procedure  called
             "prompt2".

             During  interpreter,  cooked mode is used, even if the its caller
             was using raw mode.

             If stdin is closed, interpreter will return unless the -eof  flag
             is used, in which case the subsequent argument is invoked.

       log_file [args] [[-a] file]
             If  a  filename is provided, log_file will record a transcript of
             the session (beginning at that point) in the file.  log_file will
             stop recording if no argument is given.  Any previous log file is
             closed.

             Instead of a filename, a Tcl file identifier may be  provided  by
             using  the  -open  or  -leaveopen  flags.  This is similar to the
             spawn command.  (See spawn for more info.)

             The -a flag forces output to be logged that was suppressed by the
             log_user command.

             By default, the log_file command appends to old files rather than
             truncating them, for the convenience of being able to  turn  log-
             ging  off  and  on  multiple  times  in one session.  To truncate
             files, use the -noappend flag.

             The -info flag causes log_file to return  a  description  of  the
             most recent non-info arguments given.

       log_user -info|0|1
             By  default,  the send/expect dialogue is logged to stdout (and a
             logfile if open).  The logging to stdout is disabled by the  com-
             mand  "log_user 0" and reenabled by "log_user 1".  Logging to the
             logfile is unchanged.

             The -info flag causes log_user to return  a  description  of  the
             most recent non-info arguments given.

       match_max [-d] [-i spawn_id] [size]
             defines  the  size  of  the  buffer (in bytes) used internally by
             expect.  With no size argument, the current size is returned.

             With the -d flag, the default size is set.  (The initial  default
             is  2000.)  With the -i flag, the size is set for the named spawn
             id, otherwise it is set for the current process.

       overlay [-# spawn_id] [-# spawn_id] [...] program [args]
             executes program args in place of  the  current  Expect  program,
             which  terminates.   A  bare  hyphen  argument forces a hyphen in
             front of the command name as  if  it  was  a  login  shell.   All
             spawn_ids  are closed except for those named as arguments.  These
             are mapped onto the named file identifiers.

             Spawn_ids are mapped to file identifiers for the new  program  to
             inherit.   For  example, the following line runs chess and allows
             it to be controlled by the current process - say, a chess master.

                 overlay -0 $spawn_id -1 $spawn_id -2 $spawn_id chess

             This is more efficient than "interact -u", however, it sacrifices
             the ability to do programmed interaction since the Expect process
             is no longer in control.

             Note that no controlling terminal is provided.  Thus, if you dis-
             connect or remap standard input, programs  that  do  job  control
             (shells, login, etc) will not function properly.

       parity [-d] [-i spawn_id] [value]
             defines  whether  parity  should be retained or stripped from the
             output of  spawned  processes.   If  value  is  zero,  parity  is
             stripped,  otherwise it is not stripped.  With no value argument,
             the current value is returned.

             With the -d flag, the default parity value is set.  (The  initial
             default  is  1, i.e., parity is not stripped.)  With the -i flag,
             the parity value is set for the named spawn id, otherwise  it  is
             set for the current process.

       remove_nulls [-d] [-i spawn_id] [value]
             defines  whether nulls are retained or removed from the output of
             spawned processes before pattern matching or storing in the vari-
             able  expect_out  or  interact_out.   If  value  is  1, nulls are
             removed.  If value is 0, nulls are not removed.   With  no  value
             argument, the current value is returned.

             With the -d flag, the default value is set.  (The initial default
             is 1, i.e., nulls are removed.)  With the -i flag, the  value  is
             set  for  the named spawn id, otherwise it is set for the current
             process.

             Whether or not nulls are removed, Expect will record  null  bytes
             to the log and stdout.

       send [-flags] string
             Sends string to the current process.  For example, the command

                 send "hello world\r"

             sends the characters, h e l l o <blank> w o r l d <return> to the
             current process.  (Tcl includes  a  printf-like  command  (called
             format) which can build arbitrarily complex strings.)

             Characters  are  sent  immediately  although  programs with line-
             buffered input will not read the characters until a return  char-
             acter is sent.  A return character is denoted "\r".

             The  --  flag  forces  the  next  argument to be interpreted as a
             string rather than a flag.  Any string can be  preceded  by  "--"
             whether  or  not  it actually looks like a flag.  This provides a
             reliable mechanism to  specify  variable  strings  without  being
             tripped  up  by  those  that  accidentally look like flags.  (All
             strings starting with "-" are reserved for future options.)

             The -i flag declares  that  the  string  be  sent  to  the  named
             spawn_id.   If the spawn_id is user_spawn_id, and the terminal is
             in raw mode, newlines in the string are translated to return-new-
             line  sequences  so  that  they  appear as if the terminal was in
             cooked mode.  The -raw flag disables this translation.

             The -null flag sends null characters (0 bytes).  By default,  one
             null  is  sent.   An integer may follow the -null to indicate how
             many nulls to send.

             The -break flag generates a break  condition.   This  only  makes
             sense  if  the  spawn id refers to a tty device opened via "spawn
             -open".  If you have spawned a process such as  tip,  you  should
             use tip’s convention for generating a break.

             The  -s  flag  forces  output to be sent "slowly", thus avoid the
             common situation where a computer outtypes an input  buffer  that
             was designed for a human who would never outtype the same buffer.
             This  output  is  controlled  by  the  value  of   the   variable
             "send_slow" which takes a two element list.  The first element is
             an integer that describes the number of bytes to send atomically.
             The  second element is a real number that describes the number of
             seconds by which the atomic sends must be separated.   For  exam-
             ple,  "set  send_slow  {10  .001}"  would force "send -s" to send
             strings with 1 millisecond in between each 10 characters sent.

             The -h flag forces output to be  sent  (somewhat)  like  a  human
             actually  typing.   Human-like  delays appear between the charac-
             ters.  (The algorithm is based upon a Weibull distribution,  with
             modifications  to suit this particular application.)  This output
             is controlled by the value of  the  variable  "send_human"  which
             takes  a  five  element list.  The first two elements are average
             interarrival time of characters in seconds.  The first is used by
             default.   The  second  is  used at word endings, to simulate the
             subtle pauses that occasionally occur at such  transitions.   The
             third  parameter  is  a  measure of variability where .1 is quite
             variable, 1 is reasonably variable, and 10 is  quite  invariable.
             The  extremes  are  0  to infinity.  The last two parameters are,
             respectively, a minimum and maximum interarrival time.  The mini-
             mum  and  maximum  are  used last and "clip" the final time.  The
             ultimate average can be quite different from the given average if
             the minimum and maximum clip enough values.

             As  an example, the following command emulates a fast and consis-
             tent typist:

                 set send_human {.1 .3 1 .05 2}
                 send -h "I’m hungry.  Let’s do lunch."

             while the following might be more suitable after a hangover:

                 set send_human {.4 .4 .2 .5 100}
                 send -h "Goodd party lash night!"

             Note that errors are not simulated, although you can set up error
             correction  situations yourself by embedding mistakes and correc-
             tions in a send argument.

             The flags for sending null characters, for  sending  breaks,  for
             forcing  slow  output  and  for  human-style  output are mutually
             exclusive. Only the one specified last will be used. Furthermore,
             no  string  argument  can be specified with the flags for sending
             null characters or breaks.

             It is a good idea to precede the first send to a  process  by  an
             expect.   expect  will  wait for the process to start, while send
             cannot.  In particular, if the first send  completes  before  the
             process  starts  running,  you  run  the risk of having your data
             ignored.  In situations where interactive programs offer no  ini-
             tial prompt, you can precede send by a delay as in:

                 # To avoid giving hackers hints on how to break in,
                 # this system does not prompt for an external password.
                 # Wait for 5 seconds for exec to complete
                 spawn telnet very.secure.gov
                 sleep 5
                 send password\r

             exp_send  is an alias for send.  If you are using Expectk or some
             other variant of Expect in the Tk environment, send is defined by
             Tk  for  an entirely different purpose.  exp_send is provided for
             compatibility between environments.  Similar aliases are provided
             for other Expect’s other send commands.

       send_error [-flags] string
             is  like  send,  except  that the output is sent to stderr rather
             than the current process.

       send_log [--] string
             is like send, except that the string is only sent to the log file
             (see  log_file.)   The  arguments  are  ignored if no log file is
             open.

       send_tty [-flags] string
             is like send, except that the output is sent to  /dev/tty  rather
             than the current process.

       send_user [-flags] string
             is  like  send,  except  that the output is sent to stdout rather
             than the current process.

       sleep seconds
             causes the script to sleep for the given number of seconds.  Sec-
             onds  may  be a decimal number.  Interrupts (and Tk events if you
             are using Expectk) are processed while Expect sleeps.

       spawn [args] program [args]
             creates a new process running program args.   Its  stdin,  stdout
             and  stderr are connected to Expect, so that they may be read and
             written by other Expect commands.  The connection  is  broken  by
             close  or  if  the  process itself closes any of the file identi-
             fiers.

             When a process is started by spawn, the variable spawn_id is  set
             to a descriptor referring to that process.  The process described
             by spawn_id is considered the current process.  spawn_id  may  be
             read or written, in effect providing job control.

             user_spawn_id  is a global variable containing a descriptor which
             refers to the user.  For example, when spawn_id is  set  to  this
             value, expect behaves like expect_user.

             error_spawn_id is a global variable containing a descriptor which
             refers to the standard error.  For example, when spawn_id is  set
             to this value, send behaves like send_error.

             tty_spawn_id  is  a global variable containing a descriptor which
             refers to /dev/tty.  If /dev/tty does not exist  (such  as  in  a
             cron,  at,  or  batch  script), then tty_spawn_id is not defined.
             This may be tested as:

                 if {[info vars tty_spawn_id]} {
                     # /dev/tty exists
                 } else {
                     # /dev/tty doesn’t exist
                     # probably in cron, batch, or at script
                 }


             spawn returns the UNIX process id.  If no process is  spawned,  0
             is  returned.   The  variable spawn_out(slave,name) is set to the
             name of the pty slave device.

             By default, spawn echoes the command  name  and  arguments.   The
             -noecho flag stops spawn from doing this.

             The  -console  flag causes console output to be redirected to the
             spawned process.  This is not supported on all systems.

             Internally, spawn uses a pty, initialized the  same  way  as  the
             user’s tty.  This is further initialized so that all settings are
             "sane" (according to stty(1)).   If  the  variable  stty_init  is
             defined, it is interpreted in the style of stty arguments as fur-
             ther configuration.  For example, "set stty_init raw" will  cause
             further  spawned  processes’s  terminals  to  start  in raw mode.
             -nottycopy skips the initialization  based  on  the  user’s  tty.
             -nottyinit skips the "sane" initialization.

             Normally,  spawn  takes  little  time  to execute.  If you notice
             spawn taking a significant amount of time, it is probably encoun-
             tering  ptys  that are wedged.  A number of tests are run on ptys
             to avoid entanglements with errant  processes.   (These  take  10
             seconds  per wedged pty.)  Running Expect with the -d option will
             show if Expect is encountering many ptys in odd states.   If  you
             cannot  kill the processes to which these ptys are attached, your
             only recourse may be to reboot.

             If program cannot be spawned successfully because  exec(2)  fails
             (e.g.  when  program  doesn’t  exist),  an  error message will be
             returned by the next interact or expect command as if program had
             run and produced the error message as output.  This behavior is a
             natural consequence of the implementation of spawn.   Internally,
             spawn forks, after which the spawned process has no way to commu-
             nicate with the original Expect process except  by  communication
             via the spawn_id.

             The  -open  flag  causes the next argument to be interpreted as a
             Tcl file identifier (i.e., returned by open.)  The spawn  id  can
             then  be used as if it were a spawned process.  (The file identi-
             fier should no longer be used.)  This lets you treat raw devices,
             files, and pipelines as spawned processes without using a pty.  0
             is returned to indicate there is no associated process.  When the
             connection  to  the spawned process is closed, so is the Tcl file
             identifier.  The -leaveopen flag is similar to -open except  that
             -leaveopen  causes the file identifier to be left open even after
             the spawn id is closed.

             The -pty flag causes a pty to be opened but no  process  spawned.
             0  is  returned  to  indicate  there  is  no  associated process.
             Spawn_id is set as usual.

             The variable spawn_out(slave,fd) is set to a file identifier cor-
             responding  to  the  pty  slave.   It  can be closed using "close
             -slave".

             The -ignore flag names a signal to be ignored in the spawned pro-
             cess.   Otherwise, signals get the default behavior.  Signals are
             named as in the trap command, except that each signal requires  a
             separate flag.

       strace level
             causes  following statements to be printed before being executed.
             (Tcl’s trace command traces variables.)  level indicates how  far
             down in the call stack to trace.  For example, the following com-
             mand runs Expect while tracing the first 4 levels of  calls,  but
             none below that.

                 expect -c "strace 4" script.exp


             The  -info flag causes strace to return a description of the most
             recent non-info arguments given.

       stty args
             changes terminal modes similarly to the external stty command.

             By default, the controlling terminal is accessed.   Other  termi-
             nals can be accessed by appending "< /dev/tty..." to the command.
             (Note that the arguments should not  be  grouped  into  a  single
             argument.)

             Requests  for  status return it as the result of the command.  If
             no status is requested and the controlling terminal is  accessed,
             the  previous  status of the raw and echo attributes are returned
             in a form which can later be used by the command.

             For example, the arguments raw or -cooked put the  terminal  into
             raw  mode.   The  arguments  -raw or cooked put the terminal into
             cooked mode.  The arguments echo and -echo put the terminal  into
             echo and noecho mode respectively.

             The  following  example  illustrates  how  to temporarily disable
             echoing.  This could be used in  otherwise-automatic  scripts  to
             avoid  embedding passwords in them.  (See more discussion on this
             under EXPECT HINTS below.)

                 stty -echo
                 send_user "Password: "
                 expect_user -re "(.*)\n"
                 set password $expect_out(1,string)
                 stty echo


       system args
             gives args to sh(1) as input, just as if it had been typed  as  a
             command  from  a  terminal.   Expect waits until the shell termi-
             nates.  The return status from sh is handled the  same  way  that
             exec handles its return status.

             In  contrast  to  exec  which  redirects  stdin and stdout to the
             script, system performs no redirection (other than that indicated
             by  the  string  itself).   Thus,  it is possible to use programs
             which must talk directly to /dev/tty.  For the same  reason,  the
             results of system are not recorded in the log.

       timestamp [args]
             returns  a  timestamp.   With no arguments, the number of seconds
             since the epoch is returned.

             The -format flag introduces a string which is returned  but  with
             substitutions  made  according  to  the POSIX rules for strftime.
             For example %a is replaced by an abbreviated weekday name  (i.e.,
             Sat).  Others are:
                 %a      abbreviated weekday name
                 %A      full weekday name
                 %b      abbreviated month name
                 %B      full month name
                 %c      date-time as in: Wed Oct  6 11:45:56 1993
                 %d      day of the month (01-31)
                 %H      hour (00-23)
                 %I      hour (01-12)
                 %j      day (001-366)
                 %m      month (01-12)
                 %M      minute (00-59)
                 %p      am or pm
                 %S      second (00-61)
                 %u      day (1-7, Monday is first day of week)
                 %U      week (00-53, first Sunday is first day of week one)
                 %V      week (01-53, ISO 8601 style)
                 %w      day (0-6)
                 %W      week (00-53, first Monday is first day of week one)
                 %x      date-time as in: Wed Oct  6 1993
                 %X      time as in: 23:59:59
                 %y      year (00-99)
                 %Y      year as in: 1993
                 %Z      timezone (or nothing if not determinable)
                 %%      a bare percent sign

             Other  %  specifications are undefined.  Other characters will be
             passed through untouched.  Only the C locale is supported.

             The -seconds flag introduces a number of seconds since the  epoch
             to be used as a source from which to format.  Otherwise, the cur-
             rent time is used.

             The -gmt flag forces timestamp output to use  the  GMT  timezone.
             With no flag, the local timezone is used.

       trap [[command] signals]
             causes  the  given  command to be executed upon future receipt of
             any of the given signals.  The command is executed in the  global
             scope.   If command is absent, the signal action is returned.  If
             command is the string SIG_IGN, the signals are ignored.  If  com-
             mand  is the string SIG_DFL, the signals are result to the system
             default.  signals is either a single signal or a list of signals.
             Signals  may be specified numerically or symbolically as per sig-
             nal(3).  The "SIG" prefix may be omitted.

             With no arguments (or the argument  -number),  trap  returns  the
             signal number of the trap command currently being executed.

             The  -code  flag  uses the return code of the command in place of
             whatever code Tcl was about to return when the command originally
             started running.

             The  -interp  flag  causes  the command to be evaluated using the
             interpreter active at the time the command started running rather
             than when the trap was declared.

             The  -name flag causes the trap command to return the signal name
             of the trap command currently being executed.

             The -max flag causes the trap command to return the largest  sig-
             nal number that can be set.

             For  example,  the command "trap {send_user "Ouch!"} SIGINT" will
             print "Ouch!"  each time the user presses ^C.

             By default, SIGINT (which can usually be  generated  by  pressing
             ^C) and SIGTERM cause Expect to exit.  This is due to the follow-
             ing trap, created by default when Expect starts.

                 trap exit {SIGINT SIGTERM}

             If you use the -D flag to start the debugger, SIGINT is redefined
             to  start the interactive debugger.  This is due to the following
             trap:

                 trap {exp_debug 1} SIGINT

             The debugger trap can be changed by setting the environment vari-
             able EXPECT_DEBUG_INIT to a new trap command.

             You  can,  of  course, override both of these just by adding trap
             commands to your script.  In particular, if  you  have  your  own
             "trap  exit  SIGINT", this will override the debugger trap.  This
             is useful if you want to prevent users from getting to the debug-
             ger at all.

             If  you  want to define your own trap on SIGINT but still trap to
             the debugger when it is running, use:

                 if {![exp_debug]} {trap mystuff SIGINT}

             Alternatively, you can trap to the debugger using some other sig-
             nal.

             trap  will not let you override the action for SIGALRM as this is
             used internally to Expect.  The disconnect command  sets  SIGALRM
             to  SIG_IGN  (ignore).  You can reenable this as long as you dis-
             able it during subsequent spawn commands.

             See signal(3) for more info.

       wait [args]
             delays until a spawned process (or the current process if none is
             named) terminates.

             wait normally returns a list of four integers.  The first integer
             is the pid of the process that was waited upon.  The second inte-
             ger is the corresponding spawn id.  The third integer is -1 if an
             operating system error occurred, or 0 otherwise.   If  the  third
             integer  was  0, the fourth integer is the status returned by the
             spawned process.  If the third integer was -1, the fourth integer
             is  the  value  of errno set by the operating system.  The global
             variable errorCode is also set.

             Additional elements may appear at the end  of  the  return  value
             from  wait.   An  optional  fifth  element  identifies a class of
             information.  Currently, the only possible value for this element
             is  CHILDKILLED in which case the next two values are the C-style
             signal name and a short textual description.

             The -i flag declares the process to  wait  corresponding  to  the
             named  spawn_id  (NOT the process id).  Inside a SIGCHLD handler,
             it is possible to wait for any spawned process by using the spawn
             id -1.

             The  -nowait  flag causes the wait to return immediately with the
             indication of a successful wait.  When the process exits (later),
             it  will automatically disappear without the need for an explicit
             wait.

             The wait command may also be used wait for a forked process using
             the  arguments  "-i  -1".  Unlike its use with spawned processes,
             this command can be executed at any time.  There  is  no  control
             over  which  process is reaped.  However, the return value can be
             checked for the process id.



LIBRARIES

       Expect automatically knows about  two  built-in  libraries  for  Expect
       scripts.   These  are defined by the directories named in the variables
       exp_library and exp_exec_library.  Both are meant  to  contain  utility
       files that can be used by other scripts.

       exp_library  contains architecture-independent files.  exp_exec_library
       contains architecture-dependent files.  Depending on your system,  both
       directories   may   be  totally  empty.   The  existence  of  the  file
       $exp_exec_library/cat-buffers describes whether your  /bin/cat  buffers
       by default.


PRETTY-PRINTING

       A  vgrind  definition  is available for pretty-printing Expect scripts.
       Assuming the vgrind definition supplied with the Expect distribution is
       correctly installed, you can use it as:

           vgrind -lexpect file



EXAMPLES

       It  many  not  be  apparent how to put everything together that the man
       page describes.  I encourage you to read and try out  the  examples  in
       the  example  directory  of  the Expect distribution.  Some of them are
       real programs.  Others are simply illustrative of  certain  techniques,
       and  of  course, a couple are just quick hacks.  The INSTALL file has a
       quick overview of these programs.

       The Expect papers (see SEE ALSO) are also useful.   While  some  papers
       use  syntax corresponding to earlier versions of Expect, the accompany-
       ing rationales are still valid and go into a lot more detail than  this
       man page.


CAVEATS

       Extensions  may collide with Expect’s command names.  For example, send
       is defined by Tk for an entirely different purpose.  For  this  reason,
       most of the Expect commands are also available as "exp_XXXX".  Commands
       and variables beginning with "exp", "inter", "spawn", and "timeout"  do
       not have aliases.  Use the extended command names if you need this com-
       patibility between environments.

       Expect takes a rather liberal view of scoping.   In  particular,  vari-
       ables  read  by  commands specific to the Expect program will be sought
       first from the local scope, and if not found, in the global scope.  For
       example, this obviates the need to place "global timeout" in every pro-
       cedure you write that uses expect.  On the other hand, variables  writ-
       ten  are  always in the local scope (unless a "global" command has been
       issued).  The most common problem this causes is when spawn is executed
       in  a  procedure.  Outside the procedure, spawn_id no longer exists, so
       the spawned process is no longer accessible simply because of  scoping.
       Add a "global spawn_id" to such a procedure.

       If  you  cannot  enable the multispawning capability (i.e., your system
       supports neither select (BSD *.*), poll (SVR>2), nor something  equiva-
       lent),  Expect will only be able to control a single process at a time.
       In this case, do not attempt to set spawn_id, nor  should  you  execute
       processes  via  exec  while a spawned process is running.  Furthermore,
       you will not be able to expect from multiple processes  (including  the
       user as one) at the same time.

       Terminal  parameters can have a big effect on scripts.  For example, if
       a script is written to look for echoing, it will misbehave  if  echoing
       is turned off.  For this reason, Expect forces sane terminal parameters
       by default.  Unfortunately, this can make things unpleasant  for  other
       programs.   As  an example, the emacs shell wants to change the "usual"
       mappings: newlines get mapped to newlines  instead  of  carriage-return
       newlines,  and  echoing  is  disabled.  This allows one to use emacs to
       edit the input line.  Unfortunately, Expect cannot possibly guess this.

       You  can request that Expect not override its default setting of termi-
       nal parameters, but you must then be very careful when writing  scripts
       for  such  environments.   In  the  case of emacs, avoid depending upon
       things like echoing and end-of-line mappings.

       The commands that accepted arguments braced into  a  single  list  (the
       expect  variants and interact) use a heuristic to decide if the list is
       actually one argument or many.  The heuristic can fail only in the case
       when  the list actually does represent a single argument which has mul-
       tiple embedded \n’s with non-whitespace characters between them.   This
       seems  sufficiently  improbable, however the argument "-nobrace" can be
       used to force a single argument to be handled  as  a  single  argument.
       This  could  conceivably  be  used  with machine-generated Expect code.
       Similarly, -brace forces a single argument to  be  handle  as  multiple
       patterns/actions.



BUGS

       It  was  really  tempting  to name the program "sex" (for either "Smart
       EXec" or "Send-EXpect"), but good sense (or  perhaps  just  Puritanism)
       prevailed.

       On  some systems, when a shell is spawned, it complains about not being
       able to access the tty but runs anyway.  This means your system  has  a
       mechanism  for  gaining  the  controlling  tty that Expect doesn’t know
       about.  Please find out what it is, and send this information  back  to
       me.

       Ultrix  4.1  (at least the latest versions around here) considers time-
       outs of above 1000000 to be equivalent to 0.

       Digital UNIX 4.0A (and probably other  versions)  refuses  to  allocate
       ptys  if you define a SIGCHLD handler.  See grantpt page for more info.

       IRIX 6.0 does not handle pty permissions correctly so  that  if  Expect
       attempts  to  allocate a pty previously used by someone else, it fails.
       Upgrade to IRIX 6.1.

       Telnet (verified only under SunOS 4.1.2) hangs  if  TERM  is  not  set.
       This  is  a  problem  under  cron,  at and in cgi scripts, which do not
       define TERM.  Thus, you must set it explicitly - to what type  is  usu-
       ally  irrelevant.   It  just has to be set to something!  The following
       probably suffices for most cases.

           set env(TERM) vt100


       Tip (verified only under BSDI BSD/OS 3.1 i386) hangs if SHELL and  HOME
       are  not  set.   This  is  a problem under cron, at and in cgi scripts,
       which do not define these environment variables.  Thus,  you  must  set
       them  explicitly  - to what type is usually irrelevant.  It just has to
       be set to something!  The following probably suffices for most cases.

           set env(SHELL) /bin/sh
           set env(HOME) /usr/local/bin



       Some implementations of ptys are designed so  that  the  kernel  throws
       away  any unread output after 10 to 15 seconds (actual number is imple-
       mentation-dependent) after the process has closed the file  descriptor.
       Thus Expect programs such as

           spawn date
           sleep 20
           expect

       will  fail.   To  avoid this, invoke non-interactive programs with exec
       rather than spawn.  While such situations are conceivable, in  practice
       I  have  never  encountered  a situation in which the final output of a
       truly interactive program would be lost due to this behavior.

       On the other hand, Cray UNICOS ptys throw away any unread output  imme-
       diately  after  the  process  has  closed  the file descriptor.  I have
       reported this to Cray and they are working on a fix.

       Sometimes a delay is required between a prompt and a response, such  as
       when  a  tty interface is changing UART settings or matching baud rates
       by looking for start/stop bits.  Usually, all this  is  require  is  to
       sleep  for  a second or two.  A more robust technique is to retry until
       the hardware is ready to receive input.   The  following  example  uses
       both strategies:

           send "speed 9600\r";
           sleep 1
           expect {
               timeout {send "\r"; exp_continue}
               $prompt
           }


       trap  -code  will  not  work  with any command that sits in Tcl’s event
       loop, such as sleep.  The problem is that in the event loop,  Tcl  dis-
       cards  the  return codes from async event handlers.  A workaround is to
       set a flag in the trap code.  Then check the flag immediately after the
       command (i.e., sleep).

       The  expect_background  command  ignores  -timeout arguments and has no
       concept of timeouts in general.



EXPECT HINTS

       There are a couple of things about Expect that  may  be  non-intuitive.
       This  section attempts to address some of these things with a couple of
       suggestions.

       A common expect problem is how to recognize shell prompts.  Since these
       are  customized differently by differently people and different shells,
       portably automating rlogin can be difficult without knowing the prompt.
       A  reasonable  convention  is  to have users store a regular expression
       describing their prompt (in particular, the end of it) in the  environ-
       ment  variable EXPECT_PROMPT.  Code like the following can be used.  If
       EXPECT_PROMPT doesn’t exist, the code still has a good chance of  func-
       tioning correctly.

           set prompt "(%|#|\\$) $"          ;# default prompt
           catch {set prompt $env(EXPECT_PROMPT)}

           expect -re $prompt

       I  encourage you to write expect patterns that include the end of what-
       ever you expect to see.  This avoids the  possibility  of  answering  a
       question  before  seeing  the entire thing.  In addition, while you may
       well be able to answer questions before seeing them  entirely,  if  you
       answer  early,  your answer may appear echoed back in the middle of the
       question.  In other words, the resulting dialogue will be  correct  but
       look scrambled.

       Most  prompts  include  a space character at the end.  For example, the
       prompt from ftp is ’f’, ’t’, ’p’,  ’>’  and  <blank>.   To  match  this
       prompt,  you must account for each of these characters.  It is a common
       mistake not to include the blank.  Put the blank in explicitly.

       If you use a pattern of the form X*, the * will match  all  the  output
       received  from  the  end  of X to the last thing received.  This sounds
       intuitive but can be somewhat confusing because the phrase "last  thing
       received"  can  vary  depending  upon the speed of the computer and the
       processing of I/O both by the kernel and the device driver.

       In particular, humans tend to  see  program  output  arriving  in  huge
       chunks  (atomically)  when  in reality most programs produce output one
       line at a time.  Assuming this is the case, the * in the pattern of the
       previous  paragraph  may  only  match  the end of the current line even
       though there seems to be more, because at the time of  the  match  that
       was all the output that had been received.

       expect  has no way of knowing that further output is coming unless your
       pattern specifically accounts for it.

       Even depending on line-oriented buffering is unwise.  Not only do  pro-
       grams  rarely  make  promises  about the type of buffering they do, but
       system indigestion can break output lines up so  that  lines  break  at
       seemingly  random  places.   Thus,  if  you  can  express  the last few
       characters of a prompt when writing patterns, it is wise to do so.

       If you are waiting for a pattern in the last output of  a  program  and
       the  program  emits  something  else  instead,  you will not be able to
       detect that with the timeout keyword.  The reason is that  expect  will
       not timeout - instead it will get an eof indication.  Use that instead.
       Even better, use both.  That way if that line is ever moved around, you
       won’t have to edit the line itself.

       Newlines  are  usually converted to carriage return, linefeed sequences
       when output by the terminal driver.  Thus, if you want a  pattern  that
       explicitly  matches  the  two lines, from, say, printf("foo\nbar"), you
       should use the pattern "foo\r\nbar".

       A  similar  translation  occurs  when  reading  from  the   user,   via
       expect_user.   In  this  case, when you press return, it will be trans-
       lated to a newline.  If Expect then passes that to a program which sets
       its terminal to raw mode (like telnet), there is going to be a problem,
       as the program expects a true return.  (Some programs are actually for-
       giving  in  that they will automatically translate newlines to returns,
       but most don’t.)  Unfortunately, there is no way to  find  out  that  a
       program put its terminal into raw mode.

       Rather  than  manually replacing newlines with returns, the solution is
       to use the command "stty raw", which will stop the translation.   Note,
       however,  that  this means that you will no longer get the cooked line-
       editing features.

       interact implicitly sets your terminal to raw mode so this problem will
       not arise then.

       It is often useful to store passwords (or other private information) in
       Expect scripts.  This is not recommended since anything that is  stored
       on a computer is susceptible to being accessed by anyone.  Thus, inter-
       actively prompting for passwords from a script is a smarter  idea  than
       embedding them literally.  Nonetheless, sometimes such embedding is the
       only possibility.

       Unfortunately, the UNIX file system  has  no  direct  way  of  creating
       scripts  which  are  executable  but unreadable.  Systems which support
       setgid shell scripts may indirectly simulate this as follows:

       Create the Expect script (that contains  the  secret  data)  as  usual.
       Make  its permissions be 750 (-rwxr-x---) and owned by a trusted group,
       i.e., a group which is allowed to read it.  If necessary, create a  new
       group for this purpose.  Next, create a /bin/sh script with permissions
       2751 (-rwxr-s--x) owned by the same group as before.

       The result is a script which may be  executed  (and  read)  by  anyone.
       When invoked, it runs the Expect script.


SEE ALSO

       Tcl(3), libexpect(3)
       "Exploring  Expect: A Tcl-Based Toolkit for Automating Interactive Pro-
       grams" by Don Libes, pp. 602, ISBN 1-56592-090-2,  O’Reilly  and  Asso-
       ciates, 1995.
       "expect:  Curing  Those  Uncontrollable  Fits  of Interactivity" by Don
       Libes, Proceedings of the Summer 1990 USENIX Conference, Anaheim, Cali-
       fornia, June 11-15, 1990.
       "Using  expect  to  Automate System Administration Tasks" by Don Libes,
       Proceedings of the 1990 USENIX Large Installation  Systems  Administra-
       tion Conference, Colorado Springs, Colorado, October 17-19, 1990.
       "Tcl:  An  Embeddable Command Language" by John Ousterhout, Proceedings
       of the Winter 1990 USENIX Conference, Washington, D.C., January  22-26,
       1990.
       "expect:  Scripts  for  Controlling Interactive Programs" by Don Libes,
       Computing Systems, Vol. 4, No. 2, University of California Press  Jour-
       nals, November 1991.
       "Regression  Testing  and Conformance Testing Interactive Programs", by
       Don Libes, Proceedings  of  the  Summer  1992  USENIX  Conference,  pp.
       135-144, San Antonio, TX, June 12-15, 1992.
       "Kibitz  -  Connecting  Multiple Interactive Programs Together", by Don
       Libes, Software - Practice & Experience, John Wiley & Sons,  West  Sus-
       sex, England, Vol. 23, No. 5, May, 1993.
       "A  Debugger  for  Tcl  Applications", by Don Libes, Proceedings of the
       1993 Tcl/Tk Workshop, Berkeley, CA, June 10-11, 1993.


AUTHOR

       Don Libes, National Institute of Standards and Technology


ACKNOWLEDGMENTS

       Thanks to John Ousterhout for Tcl, and Scott Paisley  for  inspiration.
       Thanks to Rob Savoye for Expect’s autoconfiguration code.

       The  HISTORY  file documents much of the evolution of expect.  It makes
       interesting reading and might give you further insight  to  this  soft-
       ware.   Thanks  to the people mentioned in it who sent me bug fixes and
       gave other assistance.

       Design and implementation of Expect was paid for in part  by  the  U.S.
       government  and  is therefore in the public domain.  However the author
       and NIST would like credit if this program and  documentation  or  por-
       tions of them are used.



                               29 December 1994                      EXPECT(1)

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