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expect (1)


expect - programmed dialogue with interactive programs, Version 5


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


EXPECT(1)                   General Commands Manual                  EXPECT(1)

       expect - programmed dialogue with interactive programs, Version 5

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

       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

       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:

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

              o   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.

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

              o   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.

              o   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.

       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

           #!/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-

       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"

       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  run-
             ning, 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.

             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
                 . . .

             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}
                     spawn priv_prog
                     expect Password:
                     send "$expect_out(1,string)\r"
                     . . .

             An advantage to using  disconnect  over  the  shell  asynchronous
             process  feature (&) is that Expect can save the terminal parame-
             ters prior to disconnection, and then later  apply  them  to  new
             ptys.   With  &, Expect does not have a chance to read the termi-
             nal'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

             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

       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-

       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.

             is an alias for send.

             is an alias for send_error.

             is an alias for send_log.

             is an alias for send_tty.

             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

             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

             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

             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

             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 buf-
             fer.  (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

             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

             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
             process 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

             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

             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
                     } incorrect {
                         send_user "invalid password or account\n"
                     } timeout {
                         send_user "connection to $host timed out\n"
                     } eof {
                         send_user \
                             "connection to host failed: $expect_out(buffer)"
                     } -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 vari-
             able 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 cur-
             rent expect to continue pattern matching after executing the cur-
             rent 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

       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

             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

       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

             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

             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_tty [expect_args]
             is like expect but it reads characters from /dev/tty  (i.e.  key-
             strokes  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.  key-
             strokes  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  key-
             strokes  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
             process 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

                 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 [clock format [clock seconds]]."}
                     \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

             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

             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 \

             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
             process 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 "[clock format [clock seconds]]: 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

             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

             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

             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

       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-

             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

             The -ignore flag names a signal to  be  ignored  in  the  spawned
             process.   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

             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 {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-

             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

             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.

       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.

       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

       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.

       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

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

       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

       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

       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}

       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.

       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

       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 charac-
       ters 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 attributes(7) for descriptions of the following attributes:

       |Availability   | shell/expect     |
       |Stability      | Uncommitted      |

       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,
       "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.

       Don Libes, National Institute of Standards and Technology

       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.

       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source        was        downloaded        from         https://source-

       Further information about this software can be found on the open source
       community website at https://core.tcl.tk/expect/.

                               29 December 1994                      EXPECT(1)