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CentOS 7.0 - man page for expect (centos section 1)

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EXPECT(1)										EXPECT(1)

NAME
       expect - programmed dialogue with interactive programs, Version 5

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

INTRODUCTION
       Expect  is  a  program  that  "talks" to other interactive programs according to a script.
       Following the script, Expect knows what can be expected from a program and what	the  cor-
       rect  response  should be.  An interpreted language provides branching and high-level con-
       trol structures to direct the dialogue.	In addition, the user can take control and inter-
       act 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	automati-
		  cally  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 character-
       ized programmatically.  Expect can also give the user back control  (without  halting  the
       program	being  controlled)  if	desired.   Similarly,  the user can return control to the
       script at any time.

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

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

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

       The  -c	flag  prefaces	a  command  to be executed before any in the script.  The command
       should be quoted to prevent being broken up by the shell.  This option may be used  multi-
       ple  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 debug-
       ger 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.

       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 use-
       fully  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 argu-
       ments 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  envi-
       ronment	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 exam-
       ple, 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 def-
       inition, etc.  Commands used here but not defined (e.g., set, if, exec) are  Tcl  commands
       (see  tcl(3)).	Expect	supports  additional commands, described below.  Unless otherwise
       specified, commands return the empty string.

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

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

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

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

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

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

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

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

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

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

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

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

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

       disconnect
	     disconnects  a  forked process from the terminal.	It continues running in the back-
	     ground.  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 back-
	     ground.

		 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 termi-
	     nal's parameters since the terminal is  already  disconnected  by	the  time  Expect
	     receives control.

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

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

	     The -noexit flag causes Expect to prepare to exit but stop short of actually return-
	     ing  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-depen-
	     dent,  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 infor-
	     mation includes every character received, and every attempt made to match	the  cur-
	     rent output against the patterns.

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

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

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

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

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

       exp_send
	     is an alias for send.

       exp_send_error
	     is an alias for send_error.

       exp_send_log
	     is an alias for send_log.

       exp_send_tty
	     is an alias for send_tty.

       exp_send_user
	     is an alias for send_user.

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

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

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

	     Second is the minor number.  Scripts written for a version with a greater minor num-
	     ber 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 ver-
	     sion.

	     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 back-
	     slash.  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  some-
	     thing  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 pat-
	     tern beginning with a "-" should be protected this way.  (All strings starting  with
	     "-" are reserved for future options.)

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

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

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

	     Regexp-style patterns follow the syntax defined by Tcl's regexp (short for  "regular
	     expression") command.  regexp patterns are introduced with the flag -re.  The previ-
	     ous 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 unnatu-
	     ral.  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 respec-
	     tively. 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  interpreta-
	     tion  of  *,  ^,  etc  is	made  (although  the  usual Tcl conventions must still be
	     observed).  Exact patterns are always unanchored.

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

	     While  reading  output,  more than 2000 bytes can force earlier bytes to be "forgot-
	     ten".  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 forgot-
	     ten characters are written to expect_out(buffer).

	     If patlist is the keyword null, and nulls are allowed  (via  the  remove_nulls  com-
	     mand), 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 sub-
	     string  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, corre-
	     sponds 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  "abbb-
	     cabkkkka\n", the result of:

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

	     is as if the following statements had executed:

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

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

	     Normally, the matched output is discarded from Expect's internal buffers.	This  may
	     be  prevented  by prefixing a pattern with the -notransfer flag.  This flag is espe-
	     cially 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 white-
	     space 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 asso-
	     ciated with any_spawn_id.

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

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

	     This  is useful for avoiding explicit loops or repeated expect statements.  The fol-
	     lowing 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 exe-
	     cuting the current action.

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

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

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

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

	     When expect_background actions are being evaluated, background  processing  for  the
	     same  spawn  id is blocked.  Background processing is unblocked when the action com-
	     pletes.  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 pat-
	     tern removes the given spawn id from the ability to  match  patterns  in  the  back-
	     ground.

       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 pat-
	     tern is matched).

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

		 expect_before -info -i $proc

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	     If the pattern is the keyword null, and nulls are allowed (via the remove_nulls com-
	     mand), 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 inter-
	     act to return to its caller.)

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

	     String-body pairs can be used as a shorthand for avoiding having to enter the inter-
	     preter 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 ter-
	     minal 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 unfor-
	     tunate 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 any-
	     thing 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 out-
	     put process as characters are read.

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

		 proc lognumber {} {
		     interact -nobuffer -re "(.*)\r" return
		     puts $log "[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 speci-
	     fied, it overrides $spawn_id.  Additional -input flags may be specified.

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

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

	     It is possible to change the processes that are being interacted with by using indi-
	     rect spawn ids.  (Indirect spawn ids are described in the section on the expect com-
	     mand.)   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  proce-
	     dure  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 (begin-
	     ning at that point) in the file.  log_file will stop recording  if  no  argument  is
	     given.  Any previous log file is closed.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       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 com-
	     plex strings.)

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

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

	     The -i flag declares that the string be sent to the named spawn_id.  If the spawn_id
	     is user_spawn_id, and the terminal is in raw mode, newlines in the string are trans-
	     lated  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 num-
	     ber that describes the number of seconds by which the atomic  sends  must	be  sepa-
	     rated.  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 sim-
	     ulate 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 val-
	     ues.

	     As an example, the following command emulates a fast and consistent typist:

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

	     while the following might be more suitable after a hangover:

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

	     Note that errors are not simulated, although you can set up error correction  situa-
	     tions 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 pur-
	     pose.  exp_send is provided for compatibility between environments.  Similar aliases
	     are provided for other Expect's other send commands.

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

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

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

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

       sleep seconds
	     causes  the script to sleep for the given number of seconds.  Seconds may be a deci-
	     mal 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 con-
	     nected 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 cur-
	     rent process.  spawn_id may be read or written, in effect providing job control.

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

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

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

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

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

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

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

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

	     Normally, spawn takes little time to execute.  If you notice spawn taking a signifi-
	     cant 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 behav-
	     ior  is  a  natural  consequence  of the implementation of spawn.	Internally, spawn
	     forks, after which the spawned process has no way to communicate with  the  original
	     Expect process except by communication via the spawn_id.

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

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

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

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

       strace level
	     causes following statements to be printed before being executed.  (Tcl's trace  com-
	     mand  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 argu-
	     ments  -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  ter-
	     minal.   Expect waits until the shell terminates.	The return status from sh is han-
	     dled 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 possi-
	     ble to use programs which must talk directly to /dev/tty.	For the same reason,  the
	     results of system are not recorded in the log.

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

	     The -format flag introduces a string which is returned but with  substitutions  made
	     according	to the POSIX rules for strftime.  For example %a is replaced by an abbre-
	     viated 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 sig-
	     nals.  The command is executed in the global scope.  If command is absent, the  sig-
	     nal  action is returned.  If command is the string SIG_IGN, the signals are ignored.
	     If command is the string SIG_DFL, the signals are	result	to  the  system  default.
	     signals  is  either  a single signal or a list of signals.  Signals may be specified
	     numerically or symbolically as per signal(3).  The "SIG" prefix may be omitted.

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

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

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

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

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

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

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

		 trap exit {SIGINT SIGTERM}

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

		 trap {exp_debug 1} SIGINT

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

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

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

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

	     Alternatively, you can trap to the debugger using some other signal.

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

	     See signal(3) for more info.

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

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

	     Additional  elements  may	appear	at  the  end  of  the return value from wait.  An
	     optional fifth element identifies a class of information.	Currently, the only  pos-
	     sible  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 suc-
	     cessful wait.  When the process exits (later), it will automatically disappear with-
	     out the need for an explicit wait.

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

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

       exp_library  contains architecture-independent files.  exp_exec_library contains architec-
       ture-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 dis-
       tribution.  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  corre-
       sponding 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 com-
       patibility between environments.

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

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

       Terminal parameters can have a big effect on scripts.  For example, if a script is written
       to  look for echoing, it will misbehave if echoing is turned off.  For this reason, Expect
       forces sane terminal parameters by default.  Unfortunately, this can make things  unpleas-
       ant  for  other programs.  As an example, the emacs shell wants to change the "usual" map-
       pings: 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  argu-
       ment  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 sin-
       gle  argument  to  be  handled  as a single argument.  This could conceivably be used with
       machine-generated Expect code.  Similarly, -brace forces a single argument to be handle as
       multiple patterns/actions.

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

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

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

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

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

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

	   set env(TERM) vt100

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

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

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

	   spawn date
	   sleep 20
	   expect

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

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

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

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

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

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

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

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

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

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

       expect has no way of knowing that further output is coming unless  your	pattern  specifi-
       cally 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  prob-
       lem,  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 exe-
       cutable but unreadable.	Systems which support setgid shell scripts may	indirectly  simu-
       late 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,  Col-
       orado, 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, Proceed-
       ings of the Summer 1992 USENIX Conference, pp. 135-144, San Antonio, TX, June 12-15, 1992.
       "Kibitz - Connecting Multiple Interactive Programs Together", by  Don  Libes,  Software	-
       Practice & Experience, John Wiley & Sons, West Sussex, England, Vol. 23, No. 5, May, 1993.
       "A  Debugger for Tcl Applications", by Don Libes, Proceedings of the 1993 Tcl/Tk Workshop,
       Berkeley, CA, June 10-11, 1993.

AUTHOR
       Don Libes, National Institute of Standards and Technology

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

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

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

					 29 December 1994				EXPECT(1)
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