expect

EXPECT(1)                   General Commands Manual                  EXPECT(1)



NAME
       expect - programmed dialogue with interactive programs, Version 5

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

INTRODUCTION
       Expect is a program that "talks" to other interactive programs
       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
                  criteria.

              •   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.

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

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

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

       The -c flag prefaces a command to be executed before any in the script.
       The command should be quoted to prevent being broken up by the shell.
       This option may be used multiple times.  Multiple commands may be
       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-
       bufferingmaystilltakeplacehoweverthisshouldn'tcauseproblemswhenreadingfromafifoorstdin.

       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/local/bin/expect --

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

       The file $exp_library/expect.rc is sourced automatically if present,
       unless the -N flag is used.  (When using Expectk, this option is
       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
       -version.)

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

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

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


COMMANDS
       Expect uses Tcl (Tool Command Language).  Tcl provides control flow
       (e.g., if, for, break), expression evaluation and several other
       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
             spawn_id.

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

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

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

             No matter whether the connection is closed implicitly or
             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.

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

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

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

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

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

             An advantage to using disconnect over the shell asynchronous
             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
             returned.

             The -noexit flag causes Expect to prepare to exit but stop short
             of actually returning control to the operating system.  The user-
             defined exit handler is run as well as Expect's own internal
             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
             reached.

       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
             information.)

       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.

       exp_send
             is an alias for send.

       exp_send_error
             is an alias for send_error.

       exp_send_log
             is an alias for send_log.

       exp_send_tty
             is an alias for send_tty.

       exp_send_user
             is an alias for send_user.

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

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

             Versions consist of three numbers separated by dots.  First is
             the major number.  Scripts written for versions of Expect with a
             different major number will almost certainly not work.
             exp_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
             manually).

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


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

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

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

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

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

             Both types of patterns are "unanchored".  This means that
             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
             affected.

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

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

             Upon matching a pattern (or eof or full_buffer), any matching and
             previously unmatched output is saved in the variable
             expect_out(buffer).  Up to 9 regexp substring matches are saved
             in the variables expect_out(1,string) through
             expect_out(9,string).  If the -indices flag is used before a
             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
                     connected
                 }

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

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

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

             This is useful for avoiding explicit loops or repeated expect
             statements.  The following example is part of a fragment to
             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
                         exp_continue
                     } incorrect {
                         send_user "invalid password or account\n"
                         exit
                     } timeout {
                         send_user "connection to $host timed out\n"
                         exit
                     } eof {
                         send_user \
                             "connection to host failed: $expect_out(buffer)"
                         exit
                     } -re $prompt
                 }

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

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


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

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

       expect_background [expect_args]
             takes the same arguments as expect, however it returns
             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
             patterns.

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

             The -info flag causes expect_before to return the current
             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
             example

                 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_before.

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

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

       fork  creates a new process.  The new process is an exact copy of the
             current Expect process.  On success, fork returns 0 to the new
             (child) process and returns the process ID of the child process
             to the parent process.  On failure (invariably due to lack of
             resources, e.g., swap space, memory), fork returns -1 to the
             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
             interactively.

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


             In string-body pairs, strings are matched in the order they are
             listed as arguments.  Strings that partially match are not sent
             to the current process in anticipation of the remainder coming.
             If characters are then entered such that there can no longer
             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
             timeout.

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

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


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

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

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

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

             If a pattern is being echoed but eventually fails to match, the
             characters are sent to the spawned process.  If the spawned
             process then echoes them, the user will see the characters twice.
             -echo is probably only appropriate in situations where the user
             is unlikely to not complete the pattern.  For example, the
             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
             "prompt2".

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

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

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

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

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

             By default, the log_file command appends to old files rather than
             truncating them, for the convenience of being able to turn
             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
             process.

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

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

                 send "hello world\r"

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

             Characters are sent immediately although programs with line-
             buffered input will not read the characters until a return
             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 very.secure.gov
                 sleep 5
                 send password\r

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

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

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

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

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

       sleep seconds
             causes the script to sleep for the given number of seconds.
             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
             identifiers.

             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
             -slave".

             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:

                 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
             signal.

             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
             wait.

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


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

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

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

           vgrind -lexpect file


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

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

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


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

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

       Ultrix 4.1 (at least the latest versions around here) considers
       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/local/bin



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

           spawn date
           sleep 20
           expect

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

       On the other hand, Cray UNICOS ptys throw away any unread output
       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}
               $prompt
           }


       trap -code will not work with any command that sits in Tcl's event
       loop, such as sleep.  The problem is that in the event loop, Tcl
       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.


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

       A common expect problem is how to recognize shell prompts.  Since these
       are customized differently by differently people and different shells,
       portably automating rlogin can be difficult without knowing the prompt.
       A reasonable convention is to have users store a regular expression
       describing their prompt (in particular, the end of it) in the
       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.

SEE ALSO
       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,
       1990.
       "Tcl: An Embeddable Command Language" by John Ousterhout, Proceedings
       of the Winter 1990 USENIX Conference, Washington, D.C., January 22-26,
       1990.
       "expect: Scripts for Controlling Interactive Programs" by Don Libes,
       Computing Systems, Vol. 4, No. 2, University of California Press
       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.

AUTHOR
       Don Libes, National Institute of Standards and Technology

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

       The HISTORY file documents much of the evolution of expect.  It makes
       interesting reading and might give you further insight to this
       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                      EXPECT(1)