1EXPECT(1)                   General Commands Manual                  EXPECT(1)
2
3
4

NAME

6       expect - programmed dialogue with interactive programs, Version 5
7

SYNOPSIS

9       expect [ -dDinN ] [ -c cmds ] [ [ -[f|b] ] cmdfile ] [ args ]
10

INTRODUCTION

12       Expect  is a program that "talks" to other interactive programs accord‐
13       ing to a script.  Following  the  script,  Expect  knows  what  can  be
14       expected  from  a  program and what the correct response should be.  An
15       interpreted language provides branching and high-level  control  struc‐
16       tures  to  direct the dialogue.  In addition, the user can take control
17       and interact directly when desired, afterward returning control to  the
18       script.
19
20       Expectk is a mixture of Expect and Tk.  It behaves just like Expect and
21       Tk's wish.  Expect can also be used directly in  C  or  C++  (that  is,
22       without Tcl).  See libexpect(3).
23
24       The name "Expect" comes from the idea of send/expect sequences popular‐
25       ized by uucp, kermit and other modem control programs.  However  unlike
26       uucp,  Expect is generalized so that it can be run as a user-level com‐
27       mand with any program and task in mind.  Expect can  actually  talk  to
28       several programs at the same time.
29
30       For example, here are some things Expect can do:
31
32              ·   Cause  your computer to dial you back, so that you can login
33                  without paying for the call.
34
35              ·   Start a game (e.g., rogue) and if the optimal  configuration
36                  doesn't  appear, restart it (again and again) until it does,
37                  then hand over control to you.
38
39              ·   Run fsck, and in response to its  questions,  answer  "yes",
40                  "no"  or  give  control  back to you, based on predetermined
41                  criteria.
42
43              ·   Connect to another network or  BBS  (e.g.,  MCI  Mail,  Com‐
44                  puServe)  and  automatically  retrieve  your mail so that it
45                  appears as if it was originally sent to your local system.
46
47              ·   Carry environment variables, current directory, or any  kind
48                  of information across rlogin, telnet, tip, su, chgrp, etc.
49
50       There  are  a  variety  of  reasons  why the shell cannot perform these
51       tasks.  (Try, you'll see.)  All are possible with Expect.
52
53       In general, Expect is useful for running  any  program  which  requires
54       interaction between the program and the user.  All that is necessary is
55       that the interaction can be characterized programmatically.  Expect can
56       also give the user back control (without halting the program being con‐
57       trolled) if desired.  Similarly, the user can  return  control  to  the
58       script at any time.
59

USAGE

61       Expect  reads  cmdfile  for  a list of commands to execute.  Expect may
62       also be invoked implicitly on systems which support the #! notation  by
63       marking  the  script  executable,  and  making  the  first line in your
64       script:
65
66           #!/usr/local/bin/expect -f
67
68       Of course, the  path  must  accurately  describe  where  Expect  lives.
69       /usr/local/bin is just an example.
70
71       The -c flag prefaces a command to be executed before any in the script.
72       The command should be quoted to prevent being broken up by  the  shell.
73       This  option may be used multiple times.  Multiple commands may be exe‐
74       cuted with a single -c by separating them  with  semicolons.   Commands
75       are  executed  in  the  order  they  appear.  (When using Expectk, this
76       option is specified as -command.)
77
78       The -d flag enables some diagnostic  output,  which  primarily  reports
79       internal  activity  of commands such as expect and interact.  This flag
80       has the same effect as "exp_internal 1" at the beginning of  an  Expect
81       script,  plus the version of Expect is printed.  (The strace command is
82       useful for tracing statements, and the  trace  command  is  useful  for
83       tracing  variable  assignments.)   (When  using Expectk, this option is
84       specified as -diag.)
85
86       The -D flag enables an interactive debugger.  An integer  value  should
87       follow.   The  debugger will take control before the next Tcl procedure
88       if the value is non-zero or if a ^C is pressed (or a breakpoint is hit,
89       or  other appropriate debugger command appears in the script).  See the
90       README file or SEE ALSO (below) for more information on  the  debugger.
91       (When using Expectk, this option is specified as -Debug.)
92
93       The -f flag prefaces a file from which to read commands from.  The flag
94       itself is optional as it is only useful when using the #! notation (see
95       above),  so  that  other arguments may be supplied on the command line.
96       (When using Expectk, this option is specified as -file.)
97
98       By default, the command file is read into memory and  executed  in  its
99       entirety.   It  is  occasionally  desirable to read files one line at a
100       time.  For example, stdin is read this way.  In order  to  force  arbi‐
101       trary  files  to  be  handled  this  way, use the -b flag.  (When using
102       Expectk, this option is specified as -buffer.)  Note that stdio-buffer‐
103       ing  may  still  take  place however this shouldn't cause problems when
104       reading from a fifo or stdin.
105
106       If the string "-" is supplied as a filename,  standard  input  is  read
107       instead.  (Use "./-" to read from a file actually named "-".)
108
109       The  -i flag causes Expect to interactively prompt for commands instead
110       of reading them from a file.  Prompting is terminated via the exit com‐
111       mand or upon EOF.  See interpreter (below) for more information.  -i is
112       assumed if neither a command file nor -c is used.  (When using Expectk,
113       this option is specified as -interactive.)
114
115       --  may  be  used to delimit the end of the options.  This is useful if
116       you want to pass an option-like argument  to  your  script  without  it
117       being  interpreted  by  Expect.   This can usefully be placed in the #!
118       line to prevent any flag-like interpretation by Expect.   For  example,
119       the  following  will leave the original arguments (including the script
120       name) in the variable argv.
121
122           #!/usr/local/bin/expect --
123
124       Note that  the  usual  getopt(3)  and  execve(2)  conventions  must  be
125       observed when adding arguments to the #! line.
126
127       The  file  $exp_library/expect.rc  is sourced automatically if present,
128       unless the -N flag is used.  (When using Expectk, this option is speci‐
129       fied  as  -NORC.)   Immediately  after  this,  the file ~/.expect.rc is
130       sourced automatically, unless the -n flag is used.  If the  environment
131       variable DOTDIR is defined, it is treated as a directory and .expect.rc
132       is read from there.  (When using Expectk, this option is  specified  as
133       -norc.)  This sourcing occurs only after executing any -c flags.
134
135       -v  causes  Expect  to  print its version number and exit.  (The corre‐
136       sponding flag in Expectk, which uses long flag names, is -version.)
137
138       Optional args are constructed into a list and stored  in  the  variable
139       named argv.  argc is initialized to the length of argv.
140
141       argv0  is  defined to be the name of the script (or binary if no script
142       is used).  For example, the following prints out the name of the script
143       and the first three arguments:
144
145           send_user "$argv0 [lrange $argv 0 2]\n"
146
147

COMMANDS

149       Expect  uses  Tcl  (Tool  Command Language).  Tcl provides control flow
150       (e.g., if, for, break), expression evaluation and  several  other  fea‐
151       tures such as recursion, procedure definition, etc.  Commands used here
152       but not defined (e.g., set, if, exec) are Tcl  commands  (see  tcl(3)).
153       Expect supports additional commands, described below.  Unless otherwise
154       specified, commands return the empty string.
155
156       Commands are listed alphabetically so that they can be quickly located.
157       However,  new users may find it easier to start by reading the descrip‐
158       tions of spawn, send, expect, and interact, in that order.
159
160       Note that the best introduction to the language (both Expect  and  Tcl)
161       is provided in the book "Exploring Expect" (see SEE ALSO below).  Exam‐
162       ples are included in this man page but they are very limited since this
163       man page is meant primarily as reference material.
164
165       Note  that in the text of this man page, "Expect" with an uppercase "E"
166       refers to the Expect program  while  "expect"  with  a  lower-case  "e"
167       refers to the expect command within the Expect program.)
168
169       close [-slave] [-onexec 0|1] [-i spawn_id]
170             closes  the  connection to the current process.  Most interactive
171             programs will detect EOF on their stdin and exit; thus close usu‐
172             ally  suffices to kill the process as well.  The -i flag declares
173             the process to close corresponding to the named spawn_id.
174
175             Both expect and interact will detect  when  the  current  process
176             exits and implicitly do a close.  But if you kill the process by,
177             say, "exec kill $pid", you will need to explicitly call close.
178
179             The -onexec flag determines whether the spawn id will  be  closed
180             in  any new spawned processes or if the process is overlayed.  To
181             leave a spawn id open, use the value 0.  A non-zero integer value
182             will force the spawn closed (the default) in any new processes.
183
184             The  -slave  flag  closes the slave associated with the spawn id.
185             (See "spawn -pty".)  When the connection is closed, the slave  is
186             automatically closed as well if still open.
187
188             No  matter whether the connection is closed implicitly or explic‐
189             itly, you should call wait to clear up the  corresponding  kernel
190             process slot.  close does not call wait since there is no guaran‐
191             tee that closing a process connection will cause it to exit.  See
192             wait below for more info.
193
194       debug [[-now] 0|1]
195             controls  a Tcl debugger allowing you to step through statements,
196             set breakpoints, etc.
197
198             With no arguments, a 1 is returned if the debugger  is  not  run‐
199             ning, otherwise a 0 is returned.
200
201             With  a  1 argument, the debugger is started.  With a 0 argument,
202             the debugger is stopped.  If a 1 argument is preceded by the -now
203             flag, the debugger is started immediately (i.e., in the middle of
204             the debug command itself).  Otherwise, the  debugger  is  started
205             with the next Tcl statement.
206
207             The  debug  command  does  not change any traps.  Compare this to
208             starting Expect with the -D flag (see above).
209
210             See the README file or SEE ALSO (below) for more  information  on
211             the debugger.
212
213       disconnect
214             disconnects  a  forked  process  from the terminal.  It continues
215             running in the background.  The process is given its own  process
216             group (if possible).  Standard I/O is redirected to /dev/null.
217
218             The  following  fragment  uses disconnect to continue running the
219             script in the background.
220
221                 if {[fork]!=0} exit
222                 disconnect
223                 . . .
224
225             The following script reads a password, and then  runs  a  program
226             every  hour  that  demands  a  password each time it is run.  The
227             script supplies the password so that you only  have  to  type  it
228             once.   (See  the stty command which demonstrates how to turn off
229             password echoing.)
230
231                 send_user "password?\ "
232                 expect_user -re "(.*)\n"
233                 for {} 1 {} {
234                     if {[fork]!=0} {sleep 3600;continue}
235                     disconnect
236                     spawn priv_prog
237                     expect Password:
238                     send "$expect_out(1,string)\r"
239                     . . .
240                     exit
241                 }
242
243             An advantage to using  disconnect  over  the  shell  asynchronous
244             process  feature (&) is that Expect can save the terminal parame‐
245             ters prior to disconnection, and then later  apply  them  to  new
246             ptys.   With  &, Expect does not have a chance to read the termi‐
247             nal's parameters since the terminal is  already  disconnected  by
248             the time Expect receives control.
249
250       exit [-opts] [status]
251             causes Expect to exit or otherwise prepare to do so.
252
253             The  -onexit  flag causes the next argument to be used as an exit
254             handler.  Without  an  argument,  the  current  exit  handler  is
255             returned.
256
257             The  -noexit flag causes Expect to prepare to exit but stop short
258             of actually returning control to the operating system.  The user-
259             defined exit handler is run as well as Expect's own internal han‐
260             dlers.  No further Expect commands should be executed.   This  is
261             useful  if you are running Expect with other Tcl extensions.  The
262             current interpreter (and main window if in  the  Tk  environment)
263             remain  so  that  other Tcl extensions can clean up.  If Expect's
264             exit is called again (however this might occur), the handlers are
265             not rerun.
266
267             Upon  exiting,  all  connections to spawned processes are closed.
268             Closure will be detected as an EOF by  spawned  processes.   exit
269             takes  no other actions beyond what the normal _exit(2) procedure
270             does.  Thus, spawned processes that do not check for EOF may con‐
271             tinue  to  run.  (A variety of conditions are important to deter‐
272             mining, for example, what signals a spawned process will be sent,
273             but   these  are  system-dependent,  typically  documented  under
274             exit(3).)  Spawned processes that continue to run will be  inher‐
275             ited by init.
276
277             status  (or 0 if not specified) is returned as the exit status of
278             Expect.  exit is implicitly executed if the end of the script  is
279             reached.
280
281       exp_continue [-continue_timer]
282             The command exp_continue allows expect itself to continue execut‐
283             ing rather than  returning  as  it  normally  would.  By  default
284             exp_continue  resets  the timeout timer. The -continue_timer flag
285             prevents timer from being restarted. (See expect for more  infor‐
286             mation.)
287
288       exp_internal [-f file] value
289             causes  further  commands to send diagnostic information internal
290             to Expect to stderr if value is non-zero.  This  output  is  dis‐
291             abled  if  value is 0.  The diagnostic information includes every
292             character received, and every attempt made to match  the  current
293             output against the patterns.
294
295             If the optional file is supplied, all normal and debugging output
296             is written to that file (regardless of the value of value).   Any
297             previous diagnostic output file is closed.
298
299             The -info flag causes exp_internal to return a description of the
300             most recent non-info arguments given.
301
302       exp_open [args] [-i spawn_id]
303             returns a Tcl file identifier that corresponds  to  the  original
304             spawn  id.   The  file  identifier can then be used as if it were
305             opened by Tcl's open command.  (The spawn id should no longer  be
306             used.  A wait should not be executed.
307
308             The  -leaveopen  flag leaves the spawn id open for access through
309             Expect commands.  A wait must be executed on the spawn id.
310
311       exp_pid [-i spawn_id]
312             returns the process id corresponding  to  the  currently  spawned
313             process.  If the -i flag is used, the pid returned corresponds to
314             that of the given spawn id.
315
316       exp_send
317             is an alias for send.
318
319       exp_send_error
320             is an alias for send_error.
321
322       exp_send_log
323             is an alias for send_log.
324
325       exp_send_tty
326             is an alias for send_tty.
327
328       exp_send_user
329             is an alias for send_user.
330
331       exp_version [[-exit] version]
332             is useful for assuring that the script  is  compatible  with  the
333             current version of Expect.
334
335             With  no  arguments,  the  current version of Expect is returned.
336             This version may then be encoded in your script.  If you actually
337             know  that you are not using features of recent versions, you can
338             specify an earlier version.
339
340             Versions consist of three numbers separated by  dots.   First  is
341             the  major number.  Scripts written for versions of Expect with a
342             different major number will almost certainly not work.   exp_ver‐
343             sion returns an error if the major numbers do not match.
344
345             Second is the minor number.  Scripts written for a version with a
346             greater minor number than the current  version  may  depend  upon
347             some new feature and might not run.  exp_version returns an error
348             if the major numbers  match,  but  the  script  minor  number  is
349             greater than that of the running Expect.
350
351             Third  is  a number that plays no part in the version comparison.
352             However, it is incremented when the Expect software  distribution
353             is  changed  in  any  way, such as by additional documentation or
354             optimization.  It is reset to 0 upon each new minor version.
355
356             With the -exit flag, Expect prints an error and exits if the ver‐
357             sion is out of date.
358
359       expect [[-opts] pat1 body1] ... [-opts] patn [bodyn]
360             waits  until  one of the patterns matches the output of a spawned
361             process, a specified time period has passed, or an end-of-file is
362             seen.  If the final body is empty, it may be omitted.
363
364             Patterns  from  the most recent expect_before command are implic‐
365             itly used before any other  patterns.   Patterns  from  the  most
366             recent  expect_after  command are implicitly used after any other
367             patterns.
368
369             If the arguments to the entire expect statement require more than
370             one  line,  all  the  arguments may be "braced" into one so as to
371             avoid terminating each line with a backslash.  In this one  case,
372             the usual Tcl substitutions will occur despite the braces.
373
374             If  a  pattern is the keyword eof, the corresponding body is exe‐
375             cuted upon end-of-file.  If a pattern is the keyword timeout, the
376             corresponding  body is executed upon timeout.  If no timeout key‐
377             word is used, an implicit null action is executed  upon  timeout.
378             The  default  timeout  period  is  10 seconds but may be set, for
379             example to 30, by the command  "set  timeout  30".   An  infinite
380             timeout  may  be designated by the value -1.  If a pattern is the
381             keyword default, the corresponding body is executed  upon  either
382             timeout or end-of-file.
383
384             If  a  pattern  matches, then the corresponding body is executed.
385             expect returns the result of the body (or the empty string if  no
386             pattern matched).  In the event that multiple patterns match, the
387             one appearing first is used to select a body.
388
389             Each time new output arrives, it is compared to each  pattern  in
390             the  order  they are listed.  Thus, you may test for absence of a
391             match by making the last pattern something guaranteed to  appear,
392             such  as  a  prompt.  In situations where there is no prompt, you
393             must use timeout (just like you would  if  you  were  interacting
394             manually).
395
396             Patterns  are  specified in three ways.  By default, patterns are
397             specified as with Tcl's string match command.  (Such patterns are
398             also  similar  to C-shell regular expressions usually referred to
399             as "glob" patterns).  The -gl flag may may  be  used  to  protect
400             patterns  that  might otherwise match expect flags from doing so.
401             Any pattern beginning with a "-" should be  protected  this  way.
402             (All strings starting with "-" are reserved for future options.)
403
404
405             For example, the following fragment looks for a successful login.
406             (Note that abort is presumed to be a procedure defined  elsewhere
407             in the script.)
408
409                 expect {
410                     busy               {puts busy\n ; exp_continue}
411                     failed             abort
412                     "invalid password" abort
413                     timeout            abort
414                     connected
415                 }
416
417             Quotes  are  necessary  on the fourth pattern since it contains a
418             space, which  would  otherwise  separate  the  pattern  from  the
419             action.   Patterns with the same action (such as the 3rd and 4th)
420             require listing the actions again.  This can be  avoid  by  using
421             regexp-style  patterns  (see below).  More information on forming
422             glob-style patterns can be found in the Tcl manual.
423
424             Regexp-style patterns follow the syntax defined by  Tcl's  regexp
425             (short  for  "regular  expression") command.  regexp patterns are
426             introduced with the  flag  -re.   The  previous  example  can  be
427             rewritten using a regexp as:
428
429                 expect {
430                     busy       {puts busy\n ; exp_continue}
431                     -re "failed|invalid password" abort
432                     timeout    abort
433                     connected
434                 }
435
436             Both  types  of  patterns are "unanchored".  This means that pat‐
437             terns do not have to match the entire string, but can  begin  and
438             end  the match anywhere in the string (as long as everything else
439             matches).  Use ^ to match the beginning of a  string,  and  $  to
440             match  the  end.   Note  that if you do not wait for the end of a
441             string, your responses can easily end up in  the  middle  of  the
442             string  as they are echoed from the spawned process.  While still
443             producing correct results, the output can look unnatural.   Thus,
444             use of $ is encouraged if you can exactly describe the characters
445             at the end of a string.
446
447             Note that in many editors, the ^ and $ match  the  beginning  and
448             end  of  lines  respectively. However, because expect is not line
449             oriented, these characters match the beginning  and  end  of  the
450             data  (as opposed to lines) currently in the expect matching buf‐
451             fer.  (Also, see the note below on "system indigestion.")
452
453             The -ex flag causes the pattern  to  be  matched  as  an  "exact"
454             string.   No  interpretation  of  *, ^, etc is made (although the
455             usual Tcl conventions must still be  observed).   Exact  patterns
456             are always unanchored.
457
458
459             The  -nocase  flag  causes  uppercase characters of the output to
460             compare as if they were lowercase characters.  The pattern is not
461             affected.
462
463             While  reading  output,  more  than  2000 bytes can force earlier
464             bytes to be "forgotten".  This may be changed with  the  function
465             match_max.  (Note that excessively large values can slow down the
466             pattern matcher.)  If patlist is full_buffer,  the  corresponding
467             body  is  executed  if  match_max bytes have been received and no
468             other patterns have matched.  Whether or not the full_buffer key‐
469             word   is   used,   the   forgotten  characters  are  written  to
470             expect_out(buffer).
471
472             If patlist is the keyword null, and nulls are  allowed  (via  the
473             remove_nulls  command),  the  corresponding body is executed if a
474             single ASCII 0 is matched.  It is not possible to match  0  bytes
475             via glob or regexp patterns.
476
477             Upon matching a pattern (or eof or full_buffer), any matching and
478             previously  unmatched   output   is   saved   in   the   variable
479             expect_out(buffer).   Up  to 9 regexp substring matches are saved
480             in      the      variables      expect_out(1,string)      through
481             expect_out(9,string).  If the -indices flag is used before a pat‐
482             tern, the starting and ending indices (in  a  form  suitable  for
483             lrange)   of   the   10  strings  are  stored  in  the  variables
484             expect_out(X,start) and expect_out(X,end) where  X  is  a  digit,
485             corresponds to the substring position in the buffer.  0 refers to
486             strings which matched the entire pattern  and  is  generated  for
487             glob  patterns  as  well  as  regexp patterns.  For example, if a
488             process has produced output of "abcdefgh\n", the result of:
489
490                 expect "cd"
491
492             is as if the following statements had executed:
493
494                 set expect_out(0,string) cd
495                 set expect_out(buffer) abcd
496
497             and "efgh\n" is left in the output buffer.  If a process produced
498             the output "abbbcabkkkka\n", the result of:
499
500                 expect -indices -re "b(b*).*(k+)"
501
502             is as if the following statements had executed:
503
504                 set expect_out(0,start) 1
505                 set expect_out(0,end) 10
506                 set expect_out(0,string) bbbcabkkkk
507                 set expect_out(1,start) 2
508                 set expect_out(1,end) 3
509                 set expect_out(1,string) bb
510                 set expect_out(2,start) 10
511                 set expect_out(2,end) 10
512                 set expect_out(2,string) k
513                 set expect_out(buffer) abbbcabkkkk
514
515             and "a\n" is left in the output buffer.  The pattern "*" (and -re
516             ".*") will flush the output buffer without reading any more  out‐
517             put from the process.
518
519             Normally,  the matched output is discarded from Expect's internal
520             buffers.  This may be prevented by prefixing a pattern  with  the
521             -notransfer  flag.  This flag is especially useful in experiment‐
522             ing (and can be  abbreviated  to  "-not"  for  convenience  while
523             experimenting).
524
525             The  spawn  id  associated  with  the  matching output (or eof or
526             full_buffer) is stored in expect_out(spawn_id).
527
528             The -timeout flag causes the current expect command  to  use  the
529             following  value  as  a timeout instead of using the value of the
530             timeout variable.
531
532             By default, patterns are matched against output from the  current
533             process,  however  the -i flag declares the output from the named
534             spawn_id list be matched against any following  patterns  (up  to
535             the  next  -i).   The spawn_id list should either be a whitespace
536             separated list of spawn_ids or a variable  referring  to  such  a
537             list of spawn_ids.
538
539             For example, the following example waits for "connected" from the
540             current process, or "busy", "failed" or "invalid  password"  from
541             the spawn_id named by $proc2.
542
543                 expect {
544                     -i $proc2 busy {puts busy\n ; exp_continue}
545                     -re "failed|invalid password" abort
546                     timeout abort
547                     connected
548                 }
549
550             The  value  of  the  global  variable any_spawn_id may be used to
551             match patterns to any spawn_ids that are named with all other  -i
552             flags in the current expect command.  The spawn_id from a -i flag
553             with no associated pattern (i.e., followed immediately by another
554             -i)  is  made  available to any other patterns in the same expect
555             command associated with any_spawn_id.
556
557             The -i flag may also name a global variable  in  which  case  the
558             variable is read for a list of spawn ids.  The variable is reread
559             whenever it changes.  This provides a way  of  changing  the  I/O
560             source  while  the  command  is in execution.  Spawn ids provided
561             this way are called "indirect" spawn ids.
562
563             Actions such as  break  and  continue  cause  control  structures
564             (i.e.,  for,  proc)  to  behave  in  the  usual way.  The command
565             exp_continue allows expect itself to  continue  executing  rather
566             than returning as it normally would.
567
568             This  is  useful  for  avoiding explicit loops or repeated expect
569             statements.  The following example is part of a fragment to auto‐
570             mate  rlogin.   The  exp_continue avoids having to write a second
571             expect statement (to look for the prompt  again)  if  the  rlogin
572             prompts for a password.
573
574                 expect {
575                     Password: {
576                         stty -echo
577                         send_user "password (for $user) on $host: "
578                         expect_user -re "(.*)\n"
579                         send_user "\n"
580                         send "$expect_out(1,string)\r"
581                         stty echo
582                         exp_continue
583                     } incorrect {
584                         send_user "invalid password or account\n"
585                         exit
586                     } timeout {
587                         send_user "connection to $host timed out\n"
588                         exit
589                     } eof {
590                         send_user \
591                             "connection to host failed: $expect_out(buffer)"
592                         exit
593                     } -re $prompt
594                 }
595
596             For  example,  the  following fragment might help a user guide an
597             interaction that is already totally automated.  In this case, the
598             terminal  is put into raw mode.  If the user presses "+", a vari‐
599             able is incremented.  If "p" is pressed, several returns are sent
600             to  the process, perhaps to poke it in some way, and "i" lets the
601             user interact with the process, effectively stealing away control
602             from  the script.  In each case, the exp_continue allows the cur‐
603             rent expect to continue pattern matching after executing the cur‐
604             rent action.
605
606                 stty raw -echo
607                 expect_after {
608                     -i $user_spawn_id
609                     "p" {send "\r\r\r"; exp_continue}
610                     "+" {incr foo; exp_continue}
611                     "i" {interact; exp_continue}
612                     "quit" exit
613                 }
614
615
616             By  default, exp_continue resets the timeout timer.  The timer is
617             not restarted, if exp_continue is called with the -continue_timer
618             flag.
619
620       expect_after [expect_args]
621             works  identically  to  the expect_before except that if patterns
622             from both expect and expect_after can match, the  expect  pattern
623             is used.  See the expect_before command for more information.
624
625       expect_background [expect_args]
626             takes  the  same  arguments as expect, however it returns immedi‐
627             ately.  Patterns are tested whenever new input arrives.  The pat‐
628             tern timeout and default are meaningless to expect_background and
629             are silently discarded.  Otherwise, the expect_background command
630             uses  expect_before  and  expect_after  patterns just like expect
631             does.
632
633             When expect_background actions are  being  evaluated,  background
634             processing for the same spawn id is blocked.  Background process‐
635             ing is unblocked when the  action  completes.   While  background
636             processing is blocked, it is possible to do a (foreground) expect
637             on the same spawn id.
638
639             It is not possible to execute an  expect  while  an  expect_back‐
640             ground is unblocked.  expect_background for a particular spawn id
641             is deleted by declaring a new  expect_background  with  the  same
642             spawn  id.   Declaring  expect_background with no pattern removes
643             the given spawn id from the ability  to  match  patterns  in  the
644             background.
645
646       expect_before [expect_args]
647             takes  the  same  arguments as expect, however it returns immedi‐
648             ately.  Pattern-action pairs from the most  recent  expect_before
649             with  the  same  spawn  id  are implicitly added to any following
650             expect commands.  If a pattern matches, it is treated  as  if  it
651             had  been specified in the expect command itself, and the associ‐
652             ated body is executed in the context of the expect  command.   If
653             patterns  from  both  expect_before  and  expect  can  match, the
654             expect_before pattern is used.
655
656             If no pattern is specified, the spawn id is not checked  for  any
657             patterns.
658
659             Unless  overridden  by  a  -i  flag, expect_before patterns match
660             against the spawn id defined at the time that  the  expect_before
661             command was executed (not when its pattern is matched).
662
663             The  -info flag causes expect_before to return the current speci‐
664             fications of what patterns it will match.  By default, it reports
665             on  the current spawn id.  An optional spawn id specification may
666             be given for information on that spawn id.  For example
667
668                 expect_before -info -i $proc
669
670             At most one spawn id specification may be given.  The flag -indi‐
671             rect  suppresses  direct  spawn  ids that come only from indirect
672             specifications.
673
674             Instead of a spawn id specification, the flag "-all"  will  cause
675             "-info" to report on all spawn ids.
676
677             The  output  of  the  -info flag can be reused as the argument to
678             expect_before.
679
680       expect_tty [expect_args]
681             is like expect but it reads characters from /dev/tty  (i.e.  key‐
682             strokes  from  the  user).   By  default, reading is performed in
683             cooked mode.  Thus, lines must end with a  return  in  order  for
684             expect  to  see them.  This may be changed via stty (see the stty
685             command below).
686
687       expect_user [expect_args]
688             is like expect but it reads  characters  from  stdin  (i.e.  key‐
689             strokes  from  the  user).   By  default, reading is performed in
690             cooked mode.  Thus, lines must end with a  return  in  order  for
691             expect  to  see them.  This may be changed via stty (see the stty
692             command below).
693
694       fork  creates a new process.  The new process is an exact copy  of  the
695             current  Expect  process.   On success, fork returns 0 to the new
696             (child) process and returns the process ID of the  child  process
697             to  the  parent  process.   On failure (invariably due to lack of
698             resources, e.g., swap space, memory), fork returns -1 to the par‐
699             ent process, and no child process is created.
700
701             Forked  processes exit via the exit command, just like the origi‐
702             nal process.  Forked processes are allowed to write  to  the  log
703             files.  If you do not disable debugging or logging in most of the
704             processes, the result can be confusing.
705
706             Some pty implementations may be confused by multiple readers  and
707             writers,  even  momentarily.   Thus,  it is safest to fork before
708             spawning processes.
709
710       interact [string1 body1] ... [stringn [bodyn]]
711             gives control of the current process to the user,  so  that  key‐
712             strokes  are  sent  to  the  current  process, and the stdout and
713             stderr of the current process are returned.
714
715             String-body pairs may be specified as arguments,  in  which  case
716             the  body  is  executed when the corresponding string is entered.
717             (By default, the string is not  sent  to  the  current  process.)
718             The interpreter command is assumed, if the final body is missing.
719
720             If  the  arguments  to the entire interact statement require more
721             than one line, all the arguments may be "braced" into one  so  as
722             to  avoid  terminating  each  line with a backslash.  In this one
723             case, the usual Tcl substitutions will occur despite the braces.
724
725             For example, the following command runs interact with the follow‐
726             ing  string-body  pairs  defined:   When ^Z is pressed, Expect is
727             suspended.  (The -reset flag restores the terminal modes.)   When
728             ^A  is  pressed,  the  user  sees "you typed a control-A" and the
729             process is sent a ^A.  When $ is pressed, the user sees the date.
730             When  ^C is pressed, Expect exits.  If "foo" is entered, the user
731             sees "bar".  When ~~ is  pressed,  the  Expect  interpreter  runs
732             interactively.
733
734                 set CTRLZ \032
735                 interact {
736                     -reset $CTRLZ {exec kill -STOP [pid]}
737                     \001   {send_user "you typed a control-A\n";
738                             send "\001"
739                            }
740                     $      {send_user "The date is [clock format [clock seconds]]."}
741                     \003   exit
742                     foo    {send_user "bar"}
743                     ~~
744                 }
745
746
747             In  string-body  pairs, strings are matched in the order they are
748             listed as arguments.  Strings that partially match are  not  sent
749             to  the  current process in anticipation of the remainder coming.
750             If characters are then entered such that there can no longer pos‐
751             sibly be a match, only the part of the string will be sent to the
752             process that cannot possibly begin another match.  Thus,  strings
753             that  are  substrings  of partial matches can match later, if the
754             original strings that  was  attempting  to  be  match  ultimately
755             fails.
756
757             By  default,  string  matching  is exact with no wild cards.  (In
758             contrast,  the  expect  command  uses  glob-style   patterns   by
759             default.)   The  -ex  flag  may  be used to protect patterns that
760             might otherwise match interact flags from doing so.  Any  pattern
761             beginning  with  a  "-"  should  be  protected  this way.    (All
762             strings starting with "-" are reserved for future options.)
763
764             The -re flag forces the string to be  interpreted  as  a  regexp-
765             style  pattern.   In this case, matching substrings are stored in
766             the variable interact_out similarly to the way expect stores  its
767             output  in  the  variable expect_out.  The -indices flag is simi‐
768             larly supported.
769
770             The pattern eof introduces an action that is executed  upon  end-
771             of-file.  A separate eof pattern may also follow the -output flag
772             in which case it is matched if an eof is detected  while  writing
773             output.   The  default  eof  action is "return", so that interact
774             simply returns upon any EOF.
775
776             The pattern timeout introduces a timeout (in seconds) and  action
777             that  is  executed after no characters have been read for a given
778             time.  The timeout pattern applies to the most recently specified
779             process.   There  is  no  default  timeout.  The special variable
780             "timeout" (used by the expect command)  has  no  affect  on  this
781             timeout.
782
783             For  example, the following statement could be used to autologout
784             users who have not typed anything for an hour but who  still  get
785             frequent system messages:
786
787                 interact -input $user_spawn_id timeout 3600 return -output \
788                     $spawn_id
789
790
791             If  the  pattern  is the keyword null, and nulls are allowed (via
792             the remove_nulls command), the corresponding body is executed  if
793             a single ASCII 0 is matched.  It is not possible to match 0 bytes
794             via glob or regexp patterns.
795
796             Prefacing a pattern with the flag  -iwrite  causes  the  variable
797             interact_out(spawn_id)  to  be  set to the spawn_id which matched
798             the pattern (or eof).
799
800             Actions such as  break  and  continue  cause  control  structures
801             (i.e.,  for,  proc)  to  behave in the usual way.  However return
802             causes interact to  return  to  its  caller,  while  inter_return
803             causes interact to cause a return in its caller.  For example, if
804             "proc  foo"  called  interact  which  then  executed  the  action
805             inter_return,  proc foo would return.  (This means that if inter‐
806             act calls interpreter interactively typing return will cause  the
807             interact  to continue, while inter_return will cause the interact
808             to return to its caller.)
809
810             During interact, raw mode is used so that all characters  may  be
811             passed  to  the current process.  If the current process does not
812             catch job control signals, it will stop if sent a stop signal (by
813             default  ^Z).   To restart it, send a continue signal (such as by
814             "kill -CONT <pid>").  If you really want to  send  a  SIGSTOP  to
815             such a process (by ^Z), consider spawning csh first and then run‐
816             ning your program.  On the other hand, if  you  want  to  send  a
817             SIGSTOP  to  Expect  itself,  first  call interpreter (perhaps by
818             using an escape character), and then press ^Z.
819
820             String-body pairs can be used as a shorthand for avoiding  having
821             to enter the interpreter and execute commands interactively.  The
822             previous terminal mode is used while the body  of  a  string-body
823             pair is being executed.
824
825             For  speed,  actions  execute in raw mode by default.  The -reset
826             flag resets the terminal to the mode it had before  interact  was
827             executed (invariably, cooked mode).  Note that characters entered
828             when the mode is being switched may be lost (an unfortunate  fea‐
829             ture of the terminal driver on some systems).  The only reason to
830             use -reset is if your action depends on running in cooked mode.
831
832             The -echo flag sends characters that match the following  pattern
833             back  to  the  process  that  generated them as each character is
834             read.  This may be useful when the user  needs  to  see  feedback
835             from partially typed patterns.
836
837             If  a  pattern is being echoed but eventually fails to match, the
838             characters are sent to  the  spawned  process.   If  the  spawned
839             process then echoes them, the user will see the characters twice.
840             -echo is probably only appropriate in situations where  the  user
841             is  unlikely  to not complete the pattern.  For example, the fol‐
842             lowing excerpt is from rftp, the recursive-ftp script, where  the
843             user is prompted to enter ~g, ~p, or ~l, to get, put, or list the
844             current directory recursively.  These are so far  away  from  the
845             normal ftp commands, that the user is unlikely to type ~ followed
846             by anything else, except mistakenly, in which case, they'll prob‐
847             ably just ignore the result anyway.
848
849                 interact {
850                     -echo ~g {getcurdirectory 1}
851                     -echo ~l {getcurdirectory 0}
852                     -echo ~p {putcurdirectory}
853                 }
854
855             The -nobuffer flag sends characters that match the following pat‐
856             tern on to the output process as characters are read.
857
858             This is useful when you wish to let a program echo back the  pat‐
859             tern.   For example, the following might be used to monitor where
860             a person is dialing (a Hayes-style modem).  Each  time  "atd"  is
861             seen the script logs the rest of the line.
862
863                 proc lognumber {} {
864                     interact -nobuffer -re "(.*)\r" return
865                     puts $log "[clock format [clock seconds]]: dialed $interact_out(1,string)"
866                 }
867
868                 interact -nobuffer "atd" lognumber
869
870
871             During interact, previous use of log_user is ignored.  In partic‐
872             ular, interact will force its output to be logged  (sent  to  the
873             standard  output)  since  it is presumed the user doesn't wish to
874             interact blindly.
875
876             The -o flag causes any following key-body pairs to be applied  to
877             the output of the current process.  This can be useful, for exam‐
878             ple, when dealing with hosts that send unwanted characters during
879             a telnet session.
880
881             By  default,  interact  expects  the user to be writing stdin and
882             reading stdout of the Expect process itself.  The  -u  flag  (for
883             "user")  makes interact look for the user as the process named by
884             its argument (which must be a spawned id).
885
886             This allows two unrelated processes to be joined together without
887             using  an explicit loop.  To aid in debugging, Expect diagnostics
888             always go to stderr (or stdout for certain logging and  debugging
889             information).   For the same reason, the interpreter command will
890             read interactively from stdin.
891
892             For example, the following  fragment  creates  a  login  process.
893             Then  it dials the user (not shown), and finally connects the two
894             together.  Of course, any process may be substituted  for  login.
895             A  shell,  for example, would allow the user to work without sup‐
896             plying an account and password.
897
898                 spawn login
899                 set login $spawn_id
900                 spawn tip modem
901                 # dial back out to user
902                 # connect user to login
903                 interact -u $login
904
905             To send output to multiple processes, list  each  spawn  id  list
906             prefaced  by  a  -output flag.  Input for a group of output spawn
907             ids may be determined by a spawn id list  prefaced  by  a  -input
908             flag.   (Both  -input and -output may take lists in the same form
909             as the -i flag in the expect command, except that any_spawn_id is
910             not meaningful in interact.)  All following flags and strings (or
911             patterns) apply to this input until another -input flag  appears.
912             If  no  -input  appears,  -output  implies "-input $user_spawn_id
913             -output".  (Similarly, with patterns that do  not  have  -input.)
914             If  one  -input  is specified, it overrides $user_spawn_id.  If a
915             second -input is specified, it overrides  $spawn_id.   Additional
916             -input flags may be specified.
917
918             The  two  implied input processes default to having their outputs
919             specified as $spawn_id and $user_spawn_id  (in  reverse).   If  a
920             -input  flag  appears  with no -output flag, characters from that
921             process are discarded.
922
923             The -i flag introduces a replacement  for  the  current  spawn_id
924             when  no  other  -input  or  -output  flags  are used.  A -i flag
925             implies a -o flag.
926
927             It is possible to change the processes that are being  interacted
928             with  by  using  indirect  spawn  ids.   (Indirect  spawn ids are
929             described in the section on the expect command.)  Indirect  spawn
930             ids may be specified with the -i, -u, -input, or -output flags.
931
932       interpreter  [args]
933             causes  the  user to be interactively prompted for Expect and Tcl
934             commands.  The result of each command is printed.
935
936             Actions such as  break  and  continue  cause  control  structures
937             (i.e.,  for,  proc)  to  behave in the usual way.  However return
938             causes interpreter to return to its  caller,  while  inter_return
939             causes interpreter to cause a return in its caller.  For example,
940             if "proc foo" called interpreter which then executed  the  action
941             inter_return,  proc  foo  would return.  Any other command causes
942             interpreter to continue prompting for new commands.
943
944             By default, the prompt contains two integers.  The first  integer
945             describes the depth of the evaluation stack (i.e., how many times
946             Tcl_Eval has been called).  The second integer is the Tcl history
947             identifier.  The prompt can be set by defining a procedure called
948             "prompt1" whose return value  becomes  the  next  prompt.   If  a
949             statement  has  open  quotes, parens, braces, or brackets, a sec‐
950             ondary prompt (by default "+> ") is  issued  upon  newline.   The
951             secondary  prompt  may  be  set  by  defining  a procedure called
952             "prompt2".
953
954             During interpreter, cooked mode is used, even if the  its  caller
955             was using raw mode.
956
957             If  stdin is closed, interpreter will return unless the -eof flag
958             is used, in which case the subsequent argument is invoked.
959
960       log_file [args] [[-a] file]
961             If a filename is provided, log_file will record a  transcript  of
962             the session (beginning at that point) in the file.  log_file will
963             stop recording if no argument is given.  Any previous log file is
964             closed.
965
966             Instead  of  a filename, a Tcl file identifier may be provided by
967             using the -open or -leaveopen flags.   This  is  similar  to  the
968             spawn command.  (See spawn for more info.)
969
970             The -a flag forces output to be logged that was suppressed by the
971             log_user command.
972
973             By default, the log_file command appends to old files rather than
974             truncating  them,  for the convenience of being able to turn log‐
975             ging off and on multiple  times  in  one  session.   To  truncate
976             files, use the -noappend flag.
977
978             The  -info  flag  causes  log_file to return a description of the
979             most recent non-info arguments given.
980
981       log_user -info|0|1
982             By default, the send/expect dialogue is logged to stdout  (and  a
983             logfile  if open).  The logging to stdout is disabled by the com‐
984             mand "log_user 0" and reenabled by "log_user 1".  Logging to  the
985             logfile is unchanged.
986
987             The  -info  flag  causes  log_user to return a description of the
988             most recent non-info arguments given.
989
990       match_max [-d] [-i spawn_id] [size]
991             defines the size of the buffer  (in  bytes)  used  internally  by
992             expect.  With no size argument, the current size is returned.
993
994             With  the -d flag, the default size is set.  (The initial default
995             is 2000.)  With the -i flag, the size is set for the named  spawn
996             id, otherwise it is set for the current process.
997
998       overlay [-# spawn_id] [-# spawn_id] [...] program [args]
999             executes  program  args  in  place of the current Expect program,
1000             which terminates.  A bare hyphen  argument  forces  a  hyphen  in
1001             front  of  the  command  name  as  if  it was a login shell.  All
1002             spawn_ids are closed except for those named as arguments.   These
1003             are mapped onto the named file identifiers.
1004
1005             Spawn_ids  are  mapped to file identifiers for the new program to
1006             inherit.  For example, the following line runs chess  and  allows
1007             it to be controlled by the current process - say, a chess master.
1008
1009                 overlay -0 $spawn_id -1 $spawn_id -2 $spawn_id chess
1010
1011             This is more efficient than "interact -u", however, it sacrifices
1012             the ability to do programmed interaction since the Expect process
1013             is no longer in control.
1014
1015             Note that no controlling terminal is provided.  Thus, if you dis‐
1016             connect or remap standard input, programs  that  do  job  control
1017             (shells, login, etc) will not function properly.
1018
1019       parity [-d] [-i spawn_id] [value]
1020             defines  whether  parity  should be retained or stripped from the
1021             output of  spawned  processes.   If  value  is  zero,  parity  is
1022             stripped,  otherwise it is not stripped.  With no value argument,
1023             the current value is returned.
1024
1025             With the -d flag, the default parity value is set.  (The  initial
1026             default  is  1, i.e., parity is not stripped.)  With the -i flag,
1027             the parity value is set for the named spawn id, otherwise  it  is
1028             set for the current process.
1029
1030       remove_nulls [-d] [-i spawn_id] [value]
1031             defines  whether nulls are retained or removed from the output of
1032             spawned processes before pattern matching or storing in the vari‐
1033             able  expect_out  or  interact_out.   If  value  is  1, nulls are
1034             removed.  If value is 0, nulls are not removed.   With  no  value
1035             argument, the current value is returned.
1036
1037             With the -d flag, the default value is set.  (The initial default
1038             is 1, i.e., nulls are removed.)  With the -i flag, the  value  is
1039             set  for  the named spawn id, otherwise it is set for the current
1040             process.
1041
1042             Whether or not nulls are removed, Expect will record  null  bytes
1043             to the log and stdout.
1044
1045       send [-flags] string
1046             Sends string to the current process.  For example, the command
1047
1048                 send "hello world\r"
1049
1050             sends the characters, h e l l o <blank> w o r l d <return> to the
1051             current process.  (Tcl includes  a  printf-like  command  (called
1052             format) which can build arbitrarily complex strings.)
1053
1054             Characters  are  sent  immediately  although  programs with line-
1055             buffered input will not read the characters until a return  char‐
1056             acter is sent.  A return character is denoted "\r".
1057
1058             The  --  flag  forces  the  next  argument to be interpreted as a
1059             string rather than a flag.  Any string can be  preceded  by  "--"
1060             whether  or  not  it actually looks like a flag.  This provides a
1061             reliable mechanism to  specify  variable  strings  without  being
1062             tripped  up  by  those  that  accidentally look like flags.  (All
1063             strings starting with "-" are reserved for future options.)
1064
1065             The -i flag declares  that  the  string  be  sent  to  the  named
1066             spawn_id.   If the spawn_id is user_spawn_id, and the terminal is
1067             in raw mode, newlines in the string are translated to return-new‐
1068             line  sequences  so  that  they  appear as if the terminal was in
1069             cooked mode.  The -raw flag disables this translation.
1070
1071             The -null flag sends null characters (0 bytes).  By default,  one
1072             null  is  sent.   An integer may follow the -null to indicate how
1073             many nulls to send.
1074
1075             The -break flag generates a break  condition.   This  only  makes
1076             sense  if  the  spawn id refers to a tty device opened via "spawn
1077             -open".  If you have spawned a process such as  tip,  you  should
1078             use tip's convention for generating a break.
1079
1080             The  -s  flag  forces  output to be sent "slowly", thus avoid the
1081             common situation where a computer outtypes an input  buffer  that
1082             was designed for a human who would never outtype the same buffer.
1083             This  output  is  controlled  by  the  value  of   the   variable
1084             "send_slow" which takes a two element list.  The first element is
1085             an integer that describes the number of bytes to send atomically.
1086             The  second element is a real number that describes the number of
1087             seconds by which the atomic sends must be separated.   For  exam‐
1088             ple,  "set  send_slow  {10  .001}"  would force "send -s" to send
1089             strings with 1 millisecond in between each 10 characters sent.
1090
1091             The -h flag forces output to be  sent  (somewhat)  like  a  human
1092             actually  typing.   Human-like  delays appear between the charac‐
1093             ters.  (The algorithm is based upon a Weibull distribution,  with
1094             modifications  to suit this particular application.)  This output
1095             is controlled by the value of  the  variable  "send_human"  which
1096             takes  a  five  element list.  The first two elements are average
1097             interarrival time of characters in seconds.  The first is used by
1098             default.   The  second  is  used at word endings, to simulate the
1099             subtle pauses that occasionally occur at such  transitions.   The
1100             third  parameter  is  a  measure of variability where .1 is quite
1101             variable, 1 is reasonably variable, and 10 is  quite  invariable.
1102             The  extremes  are  0  to infinity.  The last two parameters are,
1103             respectively, a minimum and maximum interarrival time.  The mini‐
1104             mum  and  maximum  are  used last and "clip" the final time.  The
1105             ultimate average can be quite different from the given average if
1106             the minimum and maximum clip enough values.
1107
1108             As  an example, the following command emulates a fast and consis‐
1109             tent typist:
1110
1111                 set send_human {.1 .3 1 .05 2}
1112                 send -h "I'm hungry.  Let's do lunch."
1113
1114             while the following might be more suitable after a hangover:
1115
1116                 set send_human {.4 .4 .2 .5 100}
1117                 send -h "Goodd party lash night!"
1118
1119             Note that errors are not simulated, although you can set up error
1120             correction  situations yourself by embedding mistakes and correc‐
1121             tions in a send argument.
1122
1123             The flags for sending null characters, for  sending  breaks,  for
1124             forcing  slow  output  and  for  human-style  output are mutually
1125             exclusive. Only the one specified last will be used. Furthermore,
1126             no  string  argument  can be specified with the flags for sending
1127             null characters or breaks.
1128
1129             It is a good idea to precede the first send to a  process  by  an
1130             expect.   expect  will  wait for the process to start, while send
1131             cannot.  In particular, if the first send  completes  before  the
1132             process  starts  running,  you  run  the risk of having your data
1133             ignored.  In situations where interactive programs offer no  ini‐
1134             tial prompt, you can precede send by a delay as in:
1135
1136                 # To avoid giving hackers hints on how to break in,
1137                 # this system does not prompt for an external password.
1138                 # Wait for 5 seconds for exec to complete
1139                 spawn telnet very.secure.gov
1140                 sleep 5
1141                 send password\r
1142
1143             exp_send  is an alias for send.  If you are using Expectk or some
1144             other variant of Expect in the Tk environment, send is defined by
1145             Tk  for  an entirely different purpose.  exp_send is provided for
1146             compatibility between environments.  Similar aliases are provided
1147             for other Expect's other send commands.
1148
1149       send_error [-flags] string
1150             is  like  send,  except  that the output is sent to stderr rather
1151             than the current process.
1152
1153       send_log [--] string
1154             is like send, except that the string is only sent to the log file
1155             (see  log_file.)   The  arguments  are  ignored if no log file is
1156             open.
1157
1158       send_tty [-flags] string
1159             is like send, except that the output is sent to  /dev/tty  rather
1160             than the current process.
1161
1162       send_user [-flags] string
1163             is  like  send,  except  that the output is sent to stdout rather
1164             than the current process.
1165
1166       sleep seconds
1167             causes the script to sleep for the given number of seconds.  Sec‐
1168             onds  may  be a decimal number.  Interrupts (and Tk events if you
1169             are using Expectk) are processed while Expect sleeps.
1170
1171       spawn [args] program [args]
1172             creates a new process running program args.   Its  stdin,  stdout
1173             and  stderr are connected to Expect, so that they may be read and
1174             written by other Expect commands.  The connection  is  broken  by
1175             close  or  if  the  process itself closes any of the file identi‐
1176             fiers.
1177
1178             When a process is started by spawn, the variable spawn_id is  set
1179             to a descriptor referring to that process.  The process described
1180             by spawn_id is considered the current process.  spawn_id  may  be
1181             read or written, in effect providing job control.
1182
1183             user_spawn_id  is a global variable containing a descriptor which
1184             refers to the user.  For example, when spawn_id is  set  to  this
1185             value, expect behaves like expect_user.
1186
1187             error_spawn_id is a global variable containing a descriptor which
1188             refers to the standard error.  For example, when spawn_id is  set
1189             to this value, send behaves like send_error.
1190
1191             tty_spawn_id  is  a global variable containing a descriptor which
1192             refers to /dev/tty.  If /dev/tty does not exist  (such  as  in  a
1193             cron,  at,  or  batch  script), then tty_spawn_id is not defined.
1194             This may be tested as:
1195
1196                 if {[info vars tty_spawn_id]} {
1197                     # /dev/tty exists
1198                 } else {
1199                     # /dev/tty doesn't exist
1200                     # probably in cron, batch, or at script
1201                 }
1202
1203
1204             spawn returns the UNIX process id.  If no process is  spawned,  0
1205             is  returned.   The  variable spawn_out(slave,name) is set to the
1206             name of the pty slave device.
1207
1208             By default, spawn echoes the command  name  and  arguments.   The
1209             -noecho flag stops spawn from doing this.
1210
1211             The  -console  flag causes console output to be redirected to the
1212             spawned process.  This is not supported on all systems.
1213
1214             Internally, spawn uses a pty, initialized the  same  way  as  the
1215             user's tty.  This is further initialized so that all settings are
1216             "sane" (according to stty(1)).   If  the  variable  stty_init  is
1217             defined, it is interpreted in the style of stty arguments as fur‐
1218             ther configuration.  For example, "set stty_init raw" will  cause
1219             further  spawned  processes's  terminals  to  start  in raw mode.
1220             -nottycopy skips the initialization  based  on  the  user's  tty.
1221             -nottyinit skips the "sane" initialization.
1222
1223             Normally,  spawn  takes  little  time  to execute.  If you notice
1224             spawn taking a significant amount of time, it is probably encoun‐
1225             tering  ptys  that are wedged.  A number of tests are run on ptys
1226             to avoid entanglements with errant  processes.   (These  take  10
1227             seconds  per wedged pty.)  Running Expect with the -d option will
1228             show if Expect is encountering many ptys in odd states.   If  you
1229             cannot  kill the processes to which these ptys are attached, your
1230             only recourse may be to reboot.
1231
1232             If program cannot be spawned successfully because  exec(2)  fails
1233             (e.g.  when  program  doesn't  exist),  an  error message will be
1234             returned by the next interact or expect command as if program had
1235             run and produced the error message as output.  This behavior is a
1236             natural consequence of the implementation of spawn.   Internally,
1237             spawn forks, after which the spawned process has no way to commu‐
1238             nicate with the original Expect process except  by  communication
1239             via the spawn_id.
1240
1241             The  -open  flag  causes the next argument to be interpreted as a
1242             Tcl file identifier (i.e., returned by open.)  The spawn  id  can
1243             then  be used as if it were a spawned process.  (The file identi‐
1244             fier should no longer be used.)  This lets you treat raw devices,
1245             files, and pipelines as spawned processes without using a pty.  0
1246             is returned to indicate there is no associated process.  When the
1247             connection  to  the spawned process is closed, so is the Tcl file
1248             identifier.  The -leaveopen flag is similar to -open except  that
1249             -leaveopen  causes the file identifier to be left open even after
1250             the spawn id is closed.
1251
1252             The -pty flag causes a pty to be opened but no  process  spawned.
1253             0  is  returned  to  indicate  there  is  no  associated process.
1254             Spawn_id is set as usual.
1255
1256             The variable spawn_out(slave,fd) is set to a file identifier cor‐
1257             responding  to  the  pty  slave.   It  can be closed using "close
1258             -slave".
1259
1260             The -ignore flag names a signal to  be  ignored  in  the  spawned
1261             process.   Otherwise,  signals get the default behavior.  Signals
1262             are named as  in  the  trap  command,  except  that  each  signal
1263             requires a separate flag.
1264
1265       strace level
1266             causes  following statements to be printed before being executed.
1267             (Tcl's trace command traces variables.)  level indicates how  far
1268             down in the call stack to trace.  For example, the following com‐
1269             mand runs Expect while tracing the first 4 levels of  calls,  but
1270             none below that.
1271
1272                 expect -c "strace 4" script.exp
1273
1274
1275             The  -info flag causes strace to return a description of the most
1276             recent non-info arguments given.
1277
1278       stty args
1279             changes terminal modes similarly to the external stty command.
1280
1281             By default, the controlling terminal is accessed.   Other  termi‐
1282             nals can be accessed by appending "< /dev/tty..." to the command.
1283             (Note that the arguments should not  be  grouped  into  a  single
1284             argument.)
1285
1286             Requests  for  status return it as the result of the command.  If
1287             no status is requested and the controlling terminal is  accessed,
1288             the  previous  status of the raw and echo attributes are returned
1289             in a form which can later be used by the command.
1290
1291             For example, the arguments raw or -cooked put the  terminal  into
1292             raw  mode.   The  arguments  -raw or cooked put the terminal into
1293             cooked mode.  The arguments echo and -echo put the terminal  into
1294             echo and noecho mode respectively.
1295
1296             The  following  example  illustrates  how  to temporarily disable
1297             echoing.  This could be used in  otherwise-automatic  scripts  to
1298             avoid  embedding passwords in them.  (See more discussion on this
1299             under EXPECT HINTS below.)
1300
1301                 stty -echo
1302                 send_user "Password: "
1303                 expect_user -re "(.*)\n"
1304                 set password $expect_out(1,string)
1305                 stty echo
1306
1307
1308       system args
1309             gives args to sh(1) as input, just as if it had been typed  as  a
1310             command  from  a  terminal.   Expect waits until the shell termi‐
1311             nates.  The return status from sh is handled the  same  way  that
1312             exec handles its return status.
1313
1314             In  contrast  to  exec  which  redirects  stdin and stdout to the
1315             script, system performs no redirection (other than that indicated
1316             by  the  string  itself).   Thus,  it is possible to use programs
1317             which must talk directly to /dev/tty.  For the same  reason,  the
1318             results of system are not recorded in the log.
1319
1320       timestamp [args]
1321             returns  a  timestamp.   With no arguments, the number of seconds
1322             since the epoch is returned.
1323
1324             The -format flag introduces a string which is returned  but  with
1325             substitutions  made  according  to  the POSIX rules for strftime.
1326             For example %a is replaced by an abbreviated weekday name  (i.e.,
1327             Sat).  Others are:
1328                 %a      abbreviated weekday name
1329                 %A      full weekday name
1330                 %b      abbreviated month name
1331                 %B      full month name
1332                 %c      date-time as in: Wed Oct  6 11:45:56 1993
1333                 %d      day of the month (01-31)
1334                 %H      hour (00-23)
1335                 %I      hour (01-12)
1336                 %j      day (001-366)
1337                 %m      month (01-12)
1338                 %M      minute (00-59)
1339                 %p      am or pm
1340                 %S      second (00-61)
1341                 %u      day (1-7, Monday is first day of week)
1342                 %U      week (00-53, first Sunday is first day of week one)
1343                 %V      week (01-53, ISO 8601 style)
1344                 %w      day (0-6)
1345                 %W      week (00-53, first Monday is first day of week one)
1346                 %x      date-time as in: Wed Oct  6 1993
1347                 %X      time as in: 23:59:59
1348                 %y      year (00-99)
1349                 %Y      year as in: 1993
1350                 %Z      timezone (or nothing if not determinable)
1351                 %%      a bare percent sign
1352
1353             Other  %  specifications are undefined.  Other characters will be
1354             passed through untouched.  Only the C locale is supported.
1355
1356             The -seconds flag introduces a number of seconds since the  epoch
1357             to be used as a source from which to format.  Otherwise, the cur‐
1358             rent time is used.
1359
1360             The -gmt flag forces timestamp output to use  the  GMT  timezone.
1361             With no flag, the local timezone is used.
1362
1363       trap [[command] signals]
1364             causes  the  given  command to be executed upon future receipt of
1365             any of the given signals.  The command is executed in the  global
1366             scope.   If command is absent, the signal action is returned.  If
1367             command is the string SIG_IGN, the signals are ignored.  If  com‐
1368             mand  is the string SIG_DFL, the signals are result to the system
1369             default.  signals is either a single signal or a list of signals.
1370             Signals  may be specified numerically or symbolically as per sig‐
1371             nal(3).  The "SIG" prefix may be omitted.
1372
1373             With no arguments (or the argument  -number),  trap  returns  the
1374             signal number of the trap command currently being executed.
1375
1376             The  -code  flag  uses the return code of the command in place of
1377             whatever code Tcl was about to return when the command originally
1378             started running.
1379
1380             The  -interp  flag  causes  the command to be evaluated using the
1381             interpreter active at the time the command started running rather
1382             than when the trap was declared.
1383
1384             The  -name flag causes the trap command to return the signal name
1385             of the trap command currently being executed.
1386
1387             The -max flag causes the trap command to return the largest  sig‐
1388             nal number that can be set.
1389
1390             For  example,  the command "trap {send_user "Ouch!"} SIGINT" will
1391             print "Ouch!"  each time the user presses ^C.
1392
1393             By default, SIGINT (which can usually be  generated  by  pressing
1394             ^C) and SIGTERM cause Expect to exit.  This is due to the follow‐
1395             ing trap, created by default when Expect starts.
1396
1397                 trap exit {SIGINT SIGTERM}
1398
1399             If you use the -D flag to start the debugger, SIGINT is redefined
1400             to  start the interactive debugger.  This is due to the following
1401             trap:
1402
1403                 trap {exp_debug 1} SIGINT
1404
1405             The debugger trap can be changed by setting the environment vari‐
1406             able EXPECT_DEBUG_INIT to a new trap command.
1407
1408             You  can,  of  course, override both of these just by adding trap
1409             commands to your script.  In particular, if  you  have  your  own
1410             "trap  exit  SIGINT", this will override the debugger trap.  This
1411             is useful if you want to prevent users from getting to the debug‐
1412             ger at all.
1413
1414             If  you  want to define your own trap on SIGINT but still trap to
1415             the debugger when it is running, use:
1416
1417                 if {![exp_debug]} {trap mystuff SIGINT}
1418
1419             Alternatively, you can trap to the debugger using some other sig‐
1420             nal.
1421
1422             trap  will not let you override the action for SIGALRM as this is
1423             used internally to Expect.  The disconnect command  sets  SIGALRM
1424             to  SIG_IGN  (ignore).  You can reenable this as long as you dis‐
1425             able it during subsequent spawn commands.
1426
1427             See signal(3) for more info.
1428
1429       wait [args]
1430             delays until a spawned process (or the current process if none is
1431             named) terminates.
1432
1433             wait normally returns a list of four integers.  The first integer
1434             is the pid of the process that was waited upon.  The second inte‐
1435             ger is the corresponding spawn id.  The third integer is -1 if an
1436             operating system error occurred, or 0 otherwise.   If  the  third
1437             integer  was  0, the fourth integer is the status returned by the
1438             spawned process.  If the third integer was -1, the fourth integer
1439             is  the  value  of errno set by the operating system.  The global
1440             variable errorCode is also set.
1441
1442             Additional elements may appear at the end  of  the  return  value
1443             from  wait.   An  optional  fifth  element  identifies a class of
1444             information.  Currently, the only possible value for this element
1445             is  CHILDKILLED in which case the next two values are the C-style
1446             signal name and a short textual description.
1447
1448             The -i flag declares the process to  wait  corresponding  to  the
1449             named  spawn_id  (NOT the process id).  Inside a SIGCHLD handler,
1450             it is possible to wait for any spawned process by using the spawn
1451             id -1.
1452
1453             The  -nowait  flag causes the wait to return immediately with the
1454             indication of a successful wait.  When the process exits (later),
1455             it  will automatically disappear without the need for an explicit
1456             wait.
1457
1458             The wait command may also be used wait for a forked process using
1459             the  arguments  "-i  -1".  Unlike its use with spawned processes,
1460             this command can be executed at any time.  There  is  no  control
1461             over  which  process is reaped.  However, the return value can be
1462             checked for the process id.
1463
1464

LIBRARIES

1466       Expect automatically knows about  two  built-in  libraries  for  Expect
1467       scripts.   These  are defined by the directories named in the variables
1468       exp_library and exp_exec_library.  Both are meant  to  contain  utility
1469       files that can be used by other scripts.
1470
1471       exp_library  contains architecture-independent files.  exp_exec_library
1472       contains architecture-dependent files.  Depending on your system,  both
1473       directories   may   be  totally  empty.   The  existence  of  the  file
1474       $exp_exec_library/cat-buffers describes whether your  /bin/cat  buffers
1475       by default.
1476

PRETTY-PRINTING

1478       A  vgrind  definition  is available for pretty-printing Expect scripts.
1479       Assuming the vgrind definition supplied with the Expect distribution is
1480       correctly installed, you can use it as:
1481
1482           vgrind -lexpect file
1483
1484

EXAMPLES

1486       It  many  not  be  apparent how to put everything together that the man
1487       page describes.  I encourage you to read and try out  the  examples  in
1488       the  example  directory  of  the Expect distribution.  Some of them are
1489       real programs.  Others are simply illustrative of  certain  techniques,
1490       and  of  course, a couple are just quick hacks.  The INSTALL file has a
1491       quick overview of these programs.
1492
1493       The Expect papers (see SEE ALSO) are also useful.   While  some  papers
1494       use  syntax corresponding to earlier versions of Expect, the accompany‐
1495       ing rationales are still valid and go into a lot more detail than  this
1496       man page.
1497

CAVEATS

1499       Extensions  may collide with Expect's command names.  For example, send
1500       is defined by Tk for an entirely different purpose.  For  this  reason,
1501       most of the Expect commands are also available as "exp_XXXX".  Commands
1502       and variables beginning with "exp", "inter", "spawn", and "timeout"  do
1503       not have aliases.  Use the extended command names if you need this com‐
1504       patibility between environments.
1505
1506       Expect takes a rather liberal view of scoping.   In  particular,  vari‐
1507       ables  read  by  commands specific to the Expect program will be sought
1508       first from the local scope, and if not found, in the global scope.  For
1509       example, this obviates the need to place "global timeout" in every pro‐
1510       cedure you write that uses expect.  On the other hand, variables  writ‐
1511       ten  are  always in the local scope (unless a "global" command has been
1512       issued).  The most common problem this causes is when spawn is executed
1513       in  a  procedure.  Outside the procedure, spawn_id no longer exists, so
1514       the spawned process is no longer accessible simply because of  scoping.
1515       Add a "global spawn_id" to such a procedure.
1516
1517       If  you  cannot  enable the multispawning capability (i.e., your system
1518       supports neither select (BSD *.*), poll (SVR>2), nor something  equiva‐
1519       lent),  Expect will only be able to control a single process at a time.
1520       In this case, do not attempt to set spawn_id, nor  should  you  execute
1521       processes  via  exec  while a spawned process is running.  Furthermore,
1522       you will not be able to expect from multiple processes  (including  the
1523       user as one) at the same time.
1524
1525       Terminal  parameters can have a big effect on scripts.  For example, if
1526       a script is written to look for echoing, it will misbehave  if  echoing
1527       is turned off.  For this reason, Expect forces sane terminal parameters
1528       by default.  Unfortunately, this can make things unpleasant  for  other
1529       programs.   As  an example, the emacs shell wants to change the "usual"
1530       mappings: newlines get mapped to newlines  instead  of  carriage-return
1531       newlines,  and  echoing  is  disabled.  This allows one to use emacs to
1532       edit the input line.  Unfortunately, Expect cannot possibly guess this.
1533
1534       You can request that Expect not override its default setting of  termi‐
1535       nal  parameters, but you must then be very careful when writing scripts
1536       for such environments.  In the case  of  emacs,  avoid  depending  upon
1537       things like echoing and end-of-line mappings.
1538
1539       The  commands  that  accepted  arguments braced into a single list (the
1540       expect variants and interact) use a heuristic to decide if the list  is
1541       actually one argument or many.  The heuristic can fail only in the case
1542       when the list actually does represent a single argument which has  mul‐
1543       tiple  embedded \n's with non-whitespace characters between them.  This
1544       seems sufficiently improbable, however the argument "-nobrace"  can  be
1545       used  to  force  a  single argument to be handled as a single argument.
1546       This could conceivably be  used  with  machine-generated  Expect  code.
1547       Similarly,  -brace  forces  a  single argument to be handle as multiple
1548       patterns/actions.
1549
1550

BUGS

1552       It was really tempting to name the program  "sex"  (for  either  "Smart
1553       EXec"  or  "Send-EXpect"),  but good sense (or perhaps just Puritanism)
1554       prevailed.
1555
1556       On some systems, when a shell is spawned, it complains about not  being
1557       able  to  access the tty but runs anyway.  This means your system has a
1558       mechanism for gaining the controlling  tty  that  Expect  doesn't  know
1559       about.   Please  find out what it is, and send this information back to
1560       me.
1561
1562       Ultrix 4.1 (at least the latest versions around here)  considers  time‐
1563       outs of above 1000000 to be equivalent to 0.
1564
1565       Digital  UNIX  4.0A  (and  probably other versions) refuses to allocate
1566       ptys if you define a SIGCHLD handler.  See grantpt page for more info.
1567
1568       IRIX 6.0 does not handle pty permissions correctly so  that  if  Expect
1569       attempts  to  allocate a pty previously used by someone else, it fails.
1570       Upgrade to IRIX 6.1.
1571
1572       Telnet (verified only under SunOS 4.1.2) hangs  if  TERM  is  not  set.
1573       This  is  a  problem  under  cron,  at and in cgi scripts, which do not
1574       define TERM.  Thus, you must set it explicitly - to what type  is  usu‐
1575       ally  irrelevant.   It  just has to be set to something!  The following
1576       probably suffices for most cases.
1577
1578           set env(TERM) vt100
1579
1580
1581       Tip (verified only under BSDI BSD/OS 3.1 i386) hangs if SHELL and  HOME
1582       are  not  set.   This  is  a problem under cron, at and in cgi scripts,
1583       which do not define these environment variables.  Thus,  you  must  set
1584       them  explicitly  - to what type is usually irrelevant.  It just has to
1585       be set to something!  The following probably suffices for most cases.
1586
1587           set env(SHELL) /bin/sh
1588           set env(HOME) /usr/local/bin
1589
1590
1591
1592       Some implementations of ptys are designed so  that  the  kernel  throws
1593       away  any unread output after 10 to 15 seconds (actual number is imple‐
1594       mentation-dependent) after the process has closed the file  descriptor.
1595       Thus Expect programs such as
1596
1597           spawn date
1598           sleep 20
1599           expect
1600
1601       will  fail.   To  avoid this, invoke non-interactive programs with exec
1602       rather than spawn.  While such situations are conceivable, in  practice
1603       I  have  never  encountered  a situation in which the final output of a
1604       truly interactive program would be lost due to this behavior.
1605
1606       On the other hand, Cray UNICOS ptys throw away any unread output  imme‐
1607       diately  after  the  process  has  closed  the file descriptor.  I have
1608       reported this to Cray and they are working on a fix.
1609
1610       Sometimes a delay is required between a prompt and a response, such  as
1611       when  a  tty interface is changing UART settings or matching baud rates
1612       by looking for start/stop bits.  Usually, all this  is  require  is  to
1613       sleep  for  a second or two.  A more robust technique is to retry until
1614       the hardware is ready to receive input.   The  following  example  uses
1615       both strategies:
1616
1617           send "speed 9600\r";
1618           sleep 1
1619           expect {
1620               timeout {send "\r"; exp_continue}
1621               $prompt
1622           }
1623
1624
1625       trap  -code  will  not  work  with any command that sits in Tcl's event
1626       loop, such as sleep.  The problem is that in the event loop,  Tcl  dis‐
1627       cards  the  return codes from async event handlers.  A workaround is to
1628       set a flag in the trap code.  Then check the flag immediately after the
1629       command (i.e., sleep).
1630
1631       The  expect_background  command  ignores  -timeout arguments and has no
1632       concept of timeouts in general.
1633
1634

EXPECT HINTS

1636       There are a couple of things about Expect that  may  be  non-intuitive.
1637       This  section attempts to address some of these things with a couple of
1638       suggestions.
1639
1640       A common expect problem is how to recognize shell prompts.  Since these
1641       are  customized differently by differently people and different shells,
1642       portably automating rlogin can be difficult without knowing the prompt.
1643       A  reasonable  convention  is  to have users store a regular expression
1644       describing their prompt (in particular, the end of it) in the  environ‐
1645       ment  variable EXPECT_PROMPT.  Code like the following can be used.  If
1646       EXPECT_PROMPT doesn't exist, the code still has a good chance of  func‐
1647       tioning correctly.
1648
1649           set prompt "(%|#|\\$) $"          ;# default prompt
1650           catch {set prompt $env(EXPECT_PROMPT)}
1651
1652           expect -re $prompt
1653
1654       I  encourage you to write expect patterns that include the end of what‐
1655       ever you expect to see.  This avoids the  possibility  of  answering  a
1656       question  before  seeing  the entire thing.  In addition, while you may
1657       well be able to answer questions before seeing them  entirely,  if  you
1658       answer  early,  your answer may appear echoed back in the middle of the
1659       question.  In other words, the resulting dialogue will be  correct  but
1660       look scrambled.
1661
1662       Most  prompts  include  a space character at the end.  For example, the
1663       prompt from ftp is 'f', 't', 'p',  '>'  and  <blank>.   To  match  this
1664       prompt,  you must account for each of these characters.  It is a common
1665       mistake not to include the blank.  Put the blank in explicitly.
1666
1667       If you use a pattern of the form X*, the * will match  all  the  output
1668       received  from  the  end  of X to the last thing received.  This sounds
1669       intuitive but can be somewhat confusing because the phrase "last  thing
1670       received"  can  vary  depending  upon the speed of the computer and the
1671       processing of I/O both by the kernel and the device driver.
1672
1673       In particular, humans tend to  see  program  output  arriving  in  huge
1674       chunks  (atomically)  when  in reality most programs produce output one
1675       line at a time.  Assuming this is the case, the * in the pattern of the
1676       previous  paragraph  may  only  match  the end of the current line even
1677       though there seems to be more, because at the time of  the  match  that
1678       was all the output that had been received.
1679
1680       expect  has no way of knowing that further output is coming unless your
1681       pattern specifically accounts for it.
1682
1683       Even depending on line-oriented buffering is unwise.  Not only do  pro‐
1684       grams  rarely  make  promises  about the type of buffering they do, but
1685       system indigestion can break output lines up so  that  lines  break  at
1686       seemingly random places.  Thus, if you can express the last few charac‐
1687       ters of a prompt when writing patterns, it is wise to do so.
1688
1689       If you are waiting for a pattern in the last output of  a  program  and
1690       the  program  emits  something  else  instead,  you will not be able to
1691       detect that with the timeout keyword.  The reason is that  expect  will
1692       not timeout - instead it will get an eof indication.  Use that instead.
1693       Even better, use both.  That way if that line is ever moved around, you
1694       won't have to edit the line itself.
1695
1696       Newlines  are  usually converted to carriage return, linefeed sequences
1697       when output by the terminal driver.  Thus, if you want a  pattern  that
1698       explicitly  matches  the  two lines, from, say, printf("foo\nbar"), you
1699       should use the pattern "foo\r\nbar".
1700
1701       A  similar  translation  occurs  when  reading  from  the   user,   via
1702       expect_user.   In  this  case, when you press return, it will be trans‐
1703       lated to a newline.  If Expect then passes that to a program which sets
1704       its terminal to raw mode (like telnet), there is going to be a problem,
1705       as the program expects a true return.  (Some programs are actually for‐
1706       giving  in  that they will automatically translate newlines to returns,
1707       but most don't.)  Unfortunately, there is no way to  find  out  that  a
1708       program put its terminal into raw mode.
1709
1710       Rather  than  manually replacing newlines with returns, the solution is
1711       to use the command "stty raw", which will stop the translation.   Note,
1712       however,  that  this means that you will no longer get the cooked line-
1713       editing features.
1714
1715       interact implicitly sets your terminal to raw mode so this problem will
1716       not arise then.
1717
1718       It is often useful to store passwords (or other private information) in
1719       Expect scripts.  This is not recommended since anything that is  stored
1720       on a computer is susceptible to being accessed by anyone.  Thus, inter‐
1721       actively prompting for passwords from a script is a smarter  idea  than
1722       embedding them literally.  Nonetheless, sometimes such embedding is the
1723       only possibility.
1724
1725       Unfortunately, the UNIX file system  has  no  direct  way  of  creating
1726       scripts  which  are  executable  but unreadable.  Systems which support
1727       setgid shell scripts may indirectly simulate this as follows:
1728
1729       Create the Expect script (that contains  the  secret  data)  as  usual.
1730       Make  its permissions be 750 (-rwxr-x---) and owned by a trusted group,
1731       i.e., a group which is allowed to read it.  If necessary, create a  new
1732       group for this purpose.  Next, create a /bin/sh script with permissions
1733       2751 (-rwxr-s--x) owned by the same group as before.
1734
1735       The result is a script which may be  executed  (and  read)  by  anyone.
1736       When invoked, it runs the Expect script.
1737

SEE ALSO

1739       Tcl(3), libexpect(3)
1740       "Exploring  Expect: A Tcl-Based Toolkit for Automating Interactive Pro‐
1741       grams" by Don Libes, pp. 602, ISBN 1-56592-090-2,  O'Reilly  and  Asso‐
1742       ciates, 1995.
1743       "expect:  Curing  Those  Uncontrollable  Fits  of Interactivity" by Don
1744       Libes, Proceedings of the Summer 1990 USENIX Conference, Anaheim, Cali‐
1745       fornia, June 11-15, 1990.
1746       "Using  expect  to  Automate System Administration Tasks" by Don Libes,
1747       Proceedings of the 1990 USENIX Large Installation  Systems  Administra‐
1748       tion Conference, Colorado Springs, Colorado, October 17-19, 1990.
1749       "Tcl:  An  Embeddable Command Language" by John Ousterhout, Proceedings
1750       of the Winter 1990 USENIX Conference, Washington, D.C., January  22-26,
1751       1990.
1752       "expect:  Scripts  for  Controlling Interactive Programs" by Don Libes,
1753       Computing Systems, Vol. 4, No. 2, University of California Press  Jour‐
1754       nals, November 1991.
1755       "Regression  Testing  and Conformance Testing Interactive Programs", by
1756       Don Libes, Proceedings  of  the  Summer  1992  USENIX  Conference,  pp.
1757       135-144, San Antonio, TX, June 12-15, 1992.
1758       "Kibitz  -  Connecting  Multiple Interactive Programs Together", by Don
1759       Libes, Software - Practice & Experience, John Wiley & Sons,  West  Sus‐
1760       sex, England, Vol. 23, No. 5, May, 1993.
1761       "A  Debugger  for  Tcl  Applications", by Don Libes, Proceedings of the
1762       1993 Tcl/Tk Workshop, Berkeley, CA, June 10-11, 1993.
1763

AUTHOR

1765       Don Libes, National Institute of Standards and Technology
1766

ACKNOWLEDGMENTS

1768       Thanks to John Ousterhout for Tcl, and Scott Paisley  for  inspiration.
1769       Thanks to Rob Savoye for Expect's autoconfiguration code.
1770
1771       The  HISTORY  file documents much of the evolution of expect.  It makes
1772       interesting reading and might give you further insight  to  this  soft‐
1773       ware.   Thanks  to the people mentioned in it who sent me bug fixes and
1774       gave other assistance.
1775
1776       Design and implementation of Expect was paid for in part  by  the  U.S.
1777       government  and  is therefore in the public domain.  However the author
1778       and NIST would like credit if this program and  documentation  or  por‐
1779       tions of them are used.
1780
1781
1782
1783                               29 December 1994                      EXPECT(1)
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