expect-5.45.4 man page

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

     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:

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

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

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

               o   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.

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

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

          In general, Expect is useful for running any program which requires
          interaction between the program and the user.  All that is necessary
          is that the interaction can be characterized programmatically.  Expect

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          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.) Note that stdio-
          buffering may still take place however this shouldn't cause problems
          when reading from a fifo or stdin.

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          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.

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          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

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                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

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                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

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                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.

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                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

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                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.

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                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

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                    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

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                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}

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                        "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).

                                       - 13 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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

                                       - 14 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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 [clock format [clock seconds]]."}
                        \003   exit
                        foo    {send_user "bar"}
                        ~~
                    }

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

                                       - 15 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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

                                       - 16 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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

                                       - 17 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                        puts $log "[clock format [clock seconds]]: dialed $interact_out(1,string)"
                    }

                    interact -nobuffer "atd" lognumber

                During interact, previous use of log_user is ignored.  In
                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

                                       - 18 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                $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.

                                       - 19 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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.

                                       - 20 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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

                                       - 21 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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:

                                       - 22 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                    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.

                                       - 23 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

          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

                                       - 24 -       Formatted:  December 1, 2020

     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

                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.

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                                  29 December 1994

                (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

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                                  29 December 1994

                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

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                                  29 December 1994

                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

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                                  29 December 1994

                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.

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                                  29 December 1994

          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.

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                                  29 December 1994

          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.

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                                  29 December 1994

          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
              }

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                                  29 December 1994

          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

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                                  29 December 1994

          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

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     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

          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.

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     EXPECT(1)                                                         EXPECT(1)
                                  29 December 1994

          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.

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