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       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
       according 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
       structures  to  direct  the  dialogue.   In addition, the user can take
       control and interact directly when desired, afterward returning control
       to the script.

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

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

       For example, here are some things Expect can do:

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

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

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

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

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

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

       In general, Expect is useful for running  any  program  which  requires
       interaction between the program and the user.  All that is necessary is
       that the interaction can be characterized programmatically.  Expect can
       also  give  the  user  back  control (without halting the program being
       controlled) 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/bin/expect -f

       Of course, the  path  must  accurately  describe  where  Expect  lives.
       /usr/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
       executed 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
       arbitrary  files  to be handled this way, use the -b flag.  (When using
       Expectk,  this   option   is   specified   as   -buffer.)Notethatstdio-
       bufferingmaystilltakeplacehoweverthis  shouldn’t  cause  problems  when
       reading from a fifo or stdin.

       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
       command 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/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
       specified  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
       corresponding  flag  in  Expectk,  which  uses  long  flag  names,   is

       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
       features 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
       descriptions 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).
       Examples  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
             usually suffices to kill  the  process  as  well.   The  -i  flag
             declares   the  process  to  close  corresponding  to  the  named

             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
             explicitly, you should call wait to clear  up  the  corresponding
             kernel  process slot.  close does not call wait since there is no
             guarantee that closing a process  connection  will  cause  it  to
             exit.  See wait below for more info.

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

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

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

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

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

             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
             parameters prior to disconnection, and then later apply  them  to
             new  ptys.   With  &,  Expect  does not have a chance to read the
             terminal’s parameters since the terminal is already  disconnected
             by the time Expect receives control.

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

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

             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
             handlers.  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
             continue  to  run.   (A  variety  of  conditions are important to
             determining, 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
             inherited 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
             executing 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

       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
             disabled  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_version 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
             version 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
             implicitly used before any other  patterns.   Patterns  from  the
             most  recent  expect_after  command are implicitly used after any
             other patterns.

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

             If  a  pattern  is  the  keyword  eof,  the corresponding body is
             executed upon end-of-file.  If a pattern is the keyword  timeout,
             the  corresponding  body is executed upon timeout.  If no timeout
             keyword 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
             patterns  do  not  have to match the entire string, but can begin
             and end the match anywhere in the string (as long  as  everything
             else  matches).   Use ^ to match the beginning of a string, and $
             to match the end.  Note that if you do not wait for the end of  a
             string,  your  responses  can  easily end up in the middle of the
             string as they are echoed from the spawned process.  While  still
             producing  correct results, the output can look unnatural.  Thus,
             use of $ is encouraged if you can exactly describe the characters
             at the end of a string.

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

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

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

             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
             keyword  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
             pattern,  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
             output 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
             experimenting  (and  can be abbreviated to "-not" for convenience
             while experimenting).

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

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

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

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

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

             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
             automate 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
             variable  is incremented.  If "p" is pressed, several returns are
             sent to the process, perhaps to poke it in some way, and "i" lets
             the  user  interact  with  the process, effectively stealing away
             control from the script.  In each case, the  exp_continue  allows
             the  current  expect to continue pattern matching after executing
             the current action.

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

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

       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
             immediately.   Patterns  are  tested  whenever new input arrives.
             The   pattern   timeout   and   default   are   meaningless    to
             expect_background  and  are  silently  discarded.  Otherwise, the
             expect_background command  uses  expect_before  and  expect_after
             patterns just like expect does.

             When  expect_background  actions  are being evaluated, background
             processing  for  the  same  spawn  id  is  blocked.    Background
             processing   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_background  is   unblocked.    expect_background   for   a
             particular   spawn   id   is   deleted   by   declaring   a   new
             expect_background   with   the   same   spawn   id.     Declaring
             expect_background with no pattern removes the given spawn id from
             the ability to match patterns in the background.

       expect_before [expect_args]
             takes  the  same  arguments  as  expect,   however   it   returns
             immediately.    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
             associated 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
             specifications  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

                 expect_before -info -i $proc

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

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

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

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

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

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

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

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

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

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

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

             For  example,  the  following  command  runs  interact  with  the
             following  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 [exec date]."}
                     \003   exit
                     foo    {send_user "bar"}

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

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

             The -re flag forces the string to be  interpreted  as  a  regexp-
             style  pattern.   In this case, matching substrings are stored in
             the variable interact_out similarly to the way expect stores  its
             output   in  the  variable  expect_out.   The  -indices  flag  is
             similarly 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
             interact 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
             running 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
             feature of the terminal driver on some systems).  The only reason
             to use -reset is if your action  depends  on  running  in  cooked

             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
             following  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 probably 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
             pattern on to the output process as characters are read.

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

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

                 interact -nobuffer "atd" lognumber

             During  interact,  previous  use  of  log_user  is  ignored.   In
             particular,  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
             example,  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
             supplying 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
             secondary  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
             logging  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
             command  "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
             disconnect 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
             variable  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
             character 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-
             newline  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
             example,  "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
             characters.  (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
             minimum 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
             consistent 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
             corrections 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
             initial 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
                 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.
             Seconds  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

             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
             further 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
             encountering  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
             communicate  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
             identifier 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
             corresponding  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
             command 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
             terminals  can  be  accessed  by appending "< /dev/tty..." to the
             command.  (Note that the arguments should not be grouped  into  a
             single argument.)

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

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

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

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

       system args
             gives args to sh(1) as input, just as if it had been typed  as  a
             command   from   a   terminal.   Expect  waits  until  the  shell
             terminates.  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
             current 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
             command  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 signal(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
             signal 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
             following 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
             variable 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
             debugger 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

             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
             disable 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
             integer  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
       accompanying 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
       compatibility between environments.

       Expect  takes  a  rather  liberal  view  of  scoping.   In  particular,
       variables  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 procedure you write that uses  expect.   On  the  other  hand,
       variables  written  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
       equivalent),  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
       terminal 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
       multiple 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
       timeouts 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
       usually 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/bin

       Some implementations of ptys are designed so  that  the  kernel  throws
       away  any  unread  output  after  10  to  15  seconds (actual number is
       implementation-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
       immediately  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
       discards  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
       environment  variable  EXPECT_PROMPT.   Code  like the following can be
       used.  If EXPECT_PROMPT doesn’t exist, the code still has a good chance
       of functioning 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
       whatever 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
       programs  rarely make promises about the type of buffering they do, but
       system indigestion can break output lines up so  that  lines  break  at
       seemingly  random  places.   Thus,  if  you  can  express  the last few
       characters of a prompt when writing patterns, it is wise to do so.

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

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

       A  similar  translation  occurs  when  reading  from  the   user,   via
       expect_user.   In  this  case,  when  you  press  return,  it  will  be
       translated 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  forgiving  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,
       interactively 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.


       Tcl(3), libexpect(3)
       "Exploring  Expect:  A  Tcl-Based  Toolkit  for  Automating Interactive
       Programs" by Don Libes,  pp.  602,  ISBN  1-56592-090-2,  O’Reilly  and
       Associates, 1995.
       "expect:  Curing  Those  Uncontrollable  Fits  of Interactivity" by Don
       Libes, Proceedings of  the  Summer  1990  USENIX  Conference,  Anaheim,
       California, June 11-15, 1990.
       "Using  expect  to  Automate System Administration Tasks" by Don Libes,
       Proceedings   of   the   1990   USENIX   Large   Installation   Systems
       Administration  Conference,  Colorado Springs, Colorado, October 17-19,
       "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
       Journals, 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
       Sussex, 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
       software.  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
       portions of them are used.

                               29 December 1994