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expect (1)
  • >> expect (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • expect (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
  • Ключ expect обнаружен в базе ключевых слов.
         expect - programmed dialogue with interactive programs, Ver-
         sion 5
         expect [ -dDinN ] [ -c cmds ] [ -[f|b] ] cmdfile ] [ args ]
         Expect is a program that "talks" to other  interactive  pro-
         grams  according  to a script.  Following the script, Expect
         knows what can be expected  from  a  program  and  what  the
         correct  response  should  be.  An interpreted language pro-
         vides branching and high-level control structures to  direct
         the  dialogue.   In  addition, the user can take control and
         interact directly when desired, afterward returning  control
         to the script.
         Expectk is a mixture of Expect and Tk.  It behaves just like
         Expect and Tk's wish.  Expect can also be used directly in C
         or C++ (that is, without Tcl).  See libexpect(3).
         The  name  "Expect"  comes  from  the  idea  of  send/expect
         sequences  popularized  by uucp, kermit and other modem con-
         trol programs.  However unlike uucp, Expect  is  generalized
         so  that it can be run as a user-level command with any pro-
         gram and task in mind.  Expect can actually talk to  several
         programs at the same time.
         For example, here are some things Expect can do:
              o   Cause your computer to dial you back, so  that  you
                  can login without paying for the call.
              o   Start a game (e.g., rogue) and if the optimal  con-
                  figuration  doesn't  appear,  restart it (again and
                  again) until it does, then  hand  over  control  to
              o   Run fsck, and in response to its questions,  answer
                  "yes",  "no"  or give control back to you, based on
                  predetermined criteria.
              o   Connect to another network or BBS (e.g., MCI  Mail,
                  CompuServe) and automatically retrieve your mail so
                  that it appears as if it  was  originally  sent  to
                  your local system.
              o   Carry environment variables, current directory,  or
                  any kind of information across rlogin, telnet, tip,
                  su, chgrp, etc.
         There are a variety of reasons why the shell cannot  perform
         these  tasks.   (Try,  you'll  see.)   All are possible with
         In general, Expect is useful for running any  program  which
         requires  interaction between the program and the user.  All
         that is necessary is that the interaction can be  character-
         ized  programmatically.   Expect can also give the user back
         control (without halting the program  being  controlled)  if
         desired.   Similarly,  the  user  can  return control to the
         script at any time.
         Expect reads cmdfile for a  list  of  commands  to  execute.
         Expect  may also be invoked implicitly on systems which sup-
         port the #! notation by marking the script  executable,  and
         making the first line in your script:
             #!/usr/local/bin/expect -f
         Of course, the path must accurately  describe  where  Expect
         lives.  /usr/local/bin is just an example.
         The -c flag prefaces a command to be executed before any  in
         the  script.   The command should be quoted to prevent being
         broken up by the shell.  This option may  be  used  multiple
         times.   Multiple  commands may be executed with a single -c
         by separating them with semicolons.  Commands  are  executed
         in  the  order they appear. (When using Expectk, this option
         is specified as -command.)
         The -d flag enables some diagnostic output, which  primarily
         reports  internal  activity  of  commands such as expect and
         interact.  This flag has the same effect as "exp_internal 1"
         at  the  beginning  of an Expect script, plus the version of
         Expect is printed.  (The strace command is useful for  trac-
         ing  statements, and the trace command is useful for tracing
         variable assignments.)  (When using Expectk, this option  is
         specified as -diag.)
         The -D flag enables an  interactive  debugger.   An  integer
         value  should follow.  The debugger will take control before
         the next Tcl procedure if the value is non-zero or if  a  ^C
         is  pressed  (or  a  breakpoint is hit, or other appropriate
         debugger command appears in the  script).   See  the  README
         file  or  SEE  ALSO  (below)  for  more  information  on the
         debugger.  (When using Expectk, this option is specified  as
         The -f flag prefaces a file  from  which  to  read  commands
         from.  The flag itself is optional as it is only useful when
         using the #! notation (see above), so that  other  arguments
         may  be  supplied on the command line.  (When using Expectk,
         this option is specified as -file.)
         By default, the command file is read into  memory  and  exe-
         cuted in its entirety.  It is occasionally desirable to read
         files one line at a time.  For example, stdin is  read  this
         way.   In  order to force arbitrary files to be handled this
         way, use the -b flag.  (When using Expectk, this  option  is
         specified as -buffer.)
         If the string "-" is supplied as a filename, standard  input
         is  read  instead.   (Use "./-" to read from a file actually
         named "-".)
         The -i flag causes Expect to interactively prompt  for  com-
         mands  instead  of  reading  them from a file.  Prompting is
         terminated via the exit command or  upon  EOF.   See  inter-
         preter  (below) for more information.  -i is assumed if nei-
         ther a command file nor -c is used.   (When  using  Expectk,
         this option is specified as -interactive.)
         -- may be used to delimit the end of the options.   This  is
         useful  if  you want to pass an option-like argument to your
         script without it being interpreted  by  Expect.   This  can
         usefully  be  placed in the #! line to prevent any flag-like
         interpretation by Expect.  For example, the  following  will
         leave  the original arguments (including the script name) in
         the variable argv.
             #!/usr/local/bin/expect --
         Note that the usual getopt(3) and execve(2) conventions must
         be observed when adding arguments to the #! line.
         The file $exp_library/expect.rc is sourced automatically  if
         present,  unless  the  -N flag is used. (When using Expectk,
         this option is specified as -NORC.)  Immediately after this,
         the  file  ~/.expect.rc is sourced automatically, unless the
         -n flag is used.  If  the  environment  variable  DOTDIR  is
         defined, it is treated as a directory and .expect.rc is read
         from there.  (When using Expectk, this option  is  specified
         as -norc.)  This sourcing occurs only after executing any -c
         -v causes Expect to print its version number and exit.  (The
         corresponding  flag  in Expectk, which uses long flag names,
         is -version.)
         Optional args are constructed into a list and stored in  the
         variable  named  argv.  argc is initialized to the length of
         argv0 is defined to be the name of the script (or binary  if
         no  script  is used).  For example, the following prints out
         the name of the script and the first three arguments:
             send_user "$argv0 [lrange $argv 0 2]\n"
         Expect uses Tcl (Tool Command Language).  Tcl provides  con-
         trol  flow (e.g., if, for, break), expression evaluation and
         several other features such as recursion, procedure  defini-
         tion,  etc.   Commands used here but not defined (e.g., set,
         if, exec) are Tcl commands (see  tcl(3)).   Expect  supports
         additional  commands,  described  below.   Unless  otherwise
         specified, commands return the empty string.
         Commands are listed  alphabetically  so  that  they  can  be
         quickly  located.   However, new users may find it easier to
         start by reading the descriptions of  spawn,  send,  expect,
         and interact, in that order.
         Note that the best introduction to the language (both Expect
         and Tcl) is provided in the book "Exploring Expect" (see SEE
         ALSO below).  Examples are included in  this  man  page  but
         they are very limited since this man page is meant primarily
         as reference material.
         Note that in the text of this man  page,  "Expect"  with  an
         uppercase  "E"  refers  to the Expect program while "expect"
         with a lower-case "e" refers to the  expect  command  within
         the Expect program.)
         close [-slave] [-onexec 0|1] [-i spawn_id]
               closes the connection to the  current  process.   Most
               interactive  programs  will  detect EOF on their stdin
               and exit; thus close usually suffices to kill the pro-
               cess  as  well.   The  -i flag declares the process to
               close corresponding to the named spawn_id.
               Both expect and interact will detect when the  current
               process  exits  and implicitly do a close.  But if you
               kill the process by, say, "exec kill $pid",  you  will
               need to explicitly call close.
               The -onexec flag determines whether the spawn id  will
               be  closed in any new spawned processes or if the pro-
               cess is overlayed.  To leave a spawn id open, use  the
               value  0.   A  non-zero  integer  value will force the
               spawn closed (the default) in any new processes.
               The -slave flag closes the slave associated  with  the
               spawn id.  (See "spawn -pty".)  When the connection is
               closed, the slave is automatically closed as  well  if
               still open.
               No matter whether the connection is closed  implicitly
               or  explicitly,  you  should call wait to clear up the
               corresponding kernel process  slot.   close  does  not
               call  wait  since there is no guarantee that closing a
               process connection will cause it to  exit.   See  wait
               below for more info.
         debug [[-now] 0|1]
               controls a Tcl debugger allowing you to  step  through
               statements, set breakpoints, etc.
               With no arguments, a 1 is returned if the debugger  is
               not running, otherwise a 0 is returned.
               With a 1 argument, the debugger is started.  With a  0
               argument, the debugger is stopped.  If a 1 argument is
               preceded by the -now flag,  the  debugger  is  started
               immediately  (i.e., in the middle of the debug command
               itself).  Otherwise, the debugger is started with  the
               next Tcl statement.
               The debug command does not change any traps.   Compare
               this to starting Expect with the -D flag (see above).
               See the README file  or  SEE  ALSO  (below)  for  more
               information on the debugger.
               disconnects a forked process from  the  terminal.   It
               continues  running  in the background.  The process is
               given its own process group (if  possible).   Standard
               I/O is redirected to /dev/null.
               The following fragment  uses  disconnect  to  continue
               running the script in the background.
                   if {[fork]!=0} exit
                   . . .
               The following script reads a password, and then runs a
               program  every  hour that demands a password each time
               it is run.  The script supplies the password  so  that
               you  only have to type it once.  (See the stty command
               which demonstrates how to turn off password echoing.)
                   send_user "password?\ "
                   expect_user -re "(.*)\n"
                   for {} 1 {} {
                       if {[fork]!=0} {sleep 3600;continue}
                       spawn priv_prog
                       expect Password:
                       send "$expect_out(1,string)\r"
                       . . .
               An advantage to using disconnect over the shell  asyn-
               chronous  process  feature (&) is that Expect can save
               the terminal parameters prior  to  disconnection,  and
               then  later  apply  them  to new ptys.  With &, Expect
               does not have a chance to read the terminal's  parame-
               ters since the terminal is already disconnected by the
               time Expect receives control.
         exit [-opts] [status]
               causes Expect to exit or otherwise prepare to do so.
               The -onexit flag causes the next argument to  be  used
               as  an exit handler.  Without an argument, the current
               exit handler is returned.
               The -noexit flag causes Expect to prepare to exit  but
               stop  short  of  actually  returning  control  to  the
               operating system.  The user-defined  exit  handler  is
               run  as  well  as  Expect's own internal handlers.  No
               further Expect commands should be executed.   This  is
               useful if you are running Expect with other Tcl exten-
               sions.  The current interpreter (and main window if in
               the  Tk  environment)  remain so that other Tcl exten-
               sions can clean up.  If Expect's exit is called  again
               (however  this  might  occur),  the  handlers  are not
               Upon exiting, all connections to spawned processes are
               closed.  Closure will be detected as an EOF by spawned
               processes.  exit takes no other  actions  beyond  what
               the  normal  _exit(2)  procedure  does.  Thus, spawned
               processes that do not check for EOF  may  continue  to
               run.  (A variety of conditions are important to deter-
               mining, for example, what signals  a  spawned  process
               will  be  sent,  but these are system-dependent, typi-
               cally documented under  exit(3).)   Spawned  processes
               that continue to run will be inherited by init.
               status (or 0 if not specified) is returned as the exit
               status  of Expect.  exit is implicitly executed if the
               end of the script is reached.
               The command exp_continue allows expect itself to  con-
               tinue  executing  rather than returning as it normally
               would.  (See expect for more information.)
         exp_internal [-f file] value
               causes further commands to send diagnostic information
               internal  to  Expect  to  stderr if value is non-zero.
               This output is disabled if value is 0.  The diagnostic
               information  includes  every  character  received, and
               every attempt made to match the current output against
               the patterns.
               If the optional  file  is  supplied,  all  normal  and
               debugging  output  is written to that file (regardless
               of the value of value).  Any previous diagnostic  out-
               put file is closed.
               The  -info  flag  causes  exp_internal  to  return   a
               description  of  the  most  recent  non-info arguments
         exp_open [args] [-i spawn_id]
               returns a Tcl file identifier that corresponds to  the
               original  spawn  id.   The file identifier can then be
               used as if it were opened by Tcl's open command.  (The
               spawn  id should no longer be used.  A wait should not
               be executed.
               The -leaveopen flag  leaves  the  spawn  id  open  for
               access  through  Expect commands.  A wait must be exe-
               cuted on the spawn id.
         exp_pid [-i spawn_id]
               returns the process id corresponding to the  currently
               spawned  process.   If  the  -i  flag is used, the pid
               returned corresponds to that of the given spawn id.
               is an alias for send.
               is an alias for send_error.
               is an alias for send_log.
               is an alias for send_tty.
               is an alias for send_user.
         exp_version [[-exit] version]
               is useful for assuring that the script  is  compatible
               with the current version of Expect.
               With no arguments, the current version  of  Expect  is
               returned.   This  version  may then be encoded in your
               script.  If you actually know that you are  not  using
               features  of  recent versions, you can specify an ear-
               lier version.
               Versions consist of three numbers separated  by  dots.
               First  is  the major number.  Scripts written for ver-
               sions of Expect with a  different  major  number  will
               almost  certainly  not  work.   exp_version returns an
               error if the major numbers do not match.
               Second is the minor number.   Scripts  written  for  a
               version  with  a greater minor number than the current
               version may depend upon some new feature and might not
               run.   exp_version  returns  an  error  if  the  major
               numbers match, but the script minor number is  greater
               than that of the running Expect.
               Third is a number that plays no part  in  the  version
               comparison.   However,  it  is  incremented  when  the
               Expect software distribution is changed  in  any  way,
               such  as  by additional documentation or optimization.
               It is reset to 0 upon each new minor version.
               With the -exit flag, Expect prints an error and  exits
               if the version is out of date.
         expect [[-opts] pat1 body1] ... [-opts] patn [bodyn]
               waits until one of the patterns matches the output  of
               a spawned process, a specified time period has passed,
               or an end-of-file is  seen.   If  the  final  body  is
               empty, it may be omitted.
               Patterns from the most  recent  expect_before  command
               are  implicitly  used before any other patterns.  Pat-
               terns from the most recent  expect_after  command  are
               implicitly used after any other patterns.
               If  the  arguments  to  the  entire  expect  statement
               require  more  than one line, all the arguments may be
               "braced" into one so as to avoid terminating each line
               with  a  backslash.   In  this one case, the usual Tcl
               substitutions will occur despite the braces.
               If a pattern is the  keyword  eof,  the  corresponding
               body  is  executed  upon end-of-file.  If a pattern is
               the  keyword  timeout,  the  corresponding   body   is
               executed upon timeout.  If no timeout keyword is used,
               an implicit null action is executed upon timeout.  The
               default  timeout  period is 10 seconds but may be set,
               for example to 30, by the command  "set  timeout  30".
               An infinite timeout may be designated by the value -1.
               If a pattern is the keyword default, the corresponding
               body is executed upon either timeout or end-of-file.
               If a pattern matches, then the corresponding  body  is
               executed.   expect  returns the result of the body (or
               the empty string if no pattern matched).  In the event
               that  multiple patterns match, the one appearing first
               is used to select a body.
               Each time new output arrives, it is compared  to  each
               pattern  in  the order they are listed.  Thus, you may
               test for absence of a match by making the last pattern
               something  guaranteed to appear, such as a prompt.  In
               situations where there is  no  prompt,  you  must  use
               timeout  (just  like you would if you were interacting
               Patterns are specified in  three  ways.   By  default,
               patterns are specified as with Tcl's string match com-
               mand.  (Such patterns are also similar to C-shell reg-
               ular  expressions  usually  referred to as "glob" pat-
               terns).  The -gl flag may may be used to protect  pat-
               terns  that  might  otherwise  match expect flags from
               doing so.  Any pattern beginning with a "-" should  be
               protected  this  way.   (All strings starting with "-"
               are reserved for future options.)
               For example, the following fragment looks for  a  suc-
               cessful  login.   (Note that abort is presumed to be a
               procedure defined elsewhere in the script.)
                   expect {
                       busy               {puts busy\n ; exp_continue}
                       failed             abort
                       "invalid password" abort
                       timeout            abort
               Quotes are necessary on the fourth  pattern  since  it
               contains  a  space, which would otherwise separate the
               pattern from  the  action.   Patterns  with  the  same
               action  (such  as the 3rd and 4th) require listing the
               actions again.  This can be  avoid  by  using  regexp-
               style patterns (see below).  More information on form-
               ing glob-style  patterns  can  be  found  in  the  Tcl
               Regexp-style patterns follow  the  syntax  defined  by
               Tcl's regexp (short for "regular expression") command.
               regexp patterns are introduced with the flag -re.  The
               previous example can be rewritten using a regexp as:
                   expect {
                       busy       {puts busy\n ; exp_continue}
                       -re "failed|invalid password" abort
                       timeout    abort
               Both types of patterns are "unanchored".   This  means
               that  patterns do not have to match the entire string,
               but can begin and end the match anywhere in the string
               (as  long as everything else matches).  Use ^ to match
               the beginning of a string, and $  to  match  the  end.
               Note  that if you do not wait for the end of a string,
               your responses can easily end up in the middle of  the
               string  as  they  are echoed from the spawned process.
               While still producing correct results, the output  can
               look  unnatural.   Thus, use of $ is encouraged if you
               can exactly describe the characters at the  end  of  a
               Note that in many editors,  the  ^  and  $  match  the
               beginning  and  end  of  lines  respectively. However,
               because expect is not line oriented, these  characters
               match the beginning and end of the data (as opposed to
               lines)  currently  in  the  expect  matching   buffer.
               (Also, see the note below on "system indigestion.")
               The -ex flag causes the pattern to be  matched  as  an
               "exact"  string.   No  interpretation  of *, ^, etc is
               made (although the usual Tcl conventions must still be
               observed).  Exact patterns are always unanchored.
               The -nocase flag causes uppercase  characters  of  the
               output  to  compare  as if they were lowercase charac-
               ters.  The pattern is not affected.
               While reading output, more than 2000 bytes  can  force
               earlier  bytes to be "forgotten".  This may be changed
               with the function match_max.  (Note  that  excessively
               large  values  can slow down the pattern matcher.)  If
               patlist is full_buffer, the corresponding body is exe-
               cuted  if  match_max  bytes  have been received and no
               other patterns  have  matched.   Whether  or  not  the
               full_buffer  keyword is used, the forgotten characters
               are written to expect_out(buffer).
               If patlist is the keyword null, and nulls are  allowed
               (via the remove_nulls command), the corresponding body
               is executed if a single ASCII 0 is matched.  It is not
               possible to match 0 bytes via glob or regexp patterns.
               Upon matching a pattern (or eof or  full_buffer),  any
               matching  and  previously unmatched output is saved in
               the variable expect_out(buffer).  Up to 9 regexp  sub-
               string    matches   are   saved   in   the   variables
               expect_out(1,string) through expect_out(9,string).  If
               the -indices flag is used before a pattern, the start-
               ing and ending indices (in a form suitable for lrange)
               of   the  10  strings  are  stored  in  the  variables
               expect_out(X,start) and expect_out(X,end) where X is a
               digit,  corresponds  to  the substring position in the
               buffer.  0 refers to strings which matched the  entire
               pattern  and is generated for glob patterns as well as
               regexp patterns.  For example, if a process  has  pro-
               duced output of "abcdefgh\n", the result of:
                   expect "cd"
               is as if the following statements had executed:
                   set expect_out(0,string) cd
                   set expect_out(buffer) abcd
               and "efgh\n" is left in the output buffer.  If a  pro-
               cess  produced the output "abbbcabkkkka\n", the result
                   expect -indices -re "b(b*).*(k+)"
               is as if the following statements had executed:
                   set expect_out(0,start) 1
                   set expect_out(0,end) 10
                   set expect_out(0,string) bbbcabkkkk
                   set expect_out(1,start) 2
                   set expect_out(1,end) 3
                   set expect_out(1,string) bb
                   set expect_out(2,start) 10
                   set expect_out(2,end) 10
                   set expect_out(2,string) k
                   set expect_out(buffer) abbbcabkkkk
               and "a\n" is left in the output buffer.   The  pattern
               "*"  (and  -re  ".*")  will  flush  the  output buffer
               without reading any more output from the process.
               Normally,  the  matched  output  is   discarded   from
               Expect's  internal  buffers.  This may be prevented by
               prefixing a pattern with the -notransfer  flag.   This
               flag is especially useful in experimenting (and can be
               abbreviated to "-n" for convenience while  experiment-
               The spawn id associated with the matching  output  (or
               eof or full_buffer) is stored in expect_out(spawn_id).
               The -timeout flag causes the current expect command to
               use  the following value as a timeout instead of using
               the value of the timeout variable.
               By default, patterns are matched against  output  from
               the  current process, however the -i flag declares the
               output from the named spawn_id list be matched against
               any  following  patterns  (up  to  the  next -i).  The
               spawn_id list should either be a whitespace  separated
               list  of  spawn_ids  or a variable referring to such a
               list of spawn_ids.
               For example, the following  example  waits  for  "con-
               nected"  from the current process, or "busy", "failed"
               or "invalid  password"  from  the  spawn_id  named  by
                   expect {
                       -i $proc2 busy {puts busy\n ; exp_continue}
                       -re "failed|invalid password" abort
                       timeout abort
               The value of the global variable any_spawn_id  may  be
               used to match patterns to any spawn_ids that are named
               with all other -i flags in the current expect command.
               The spawn_id from a -i flag with no associated pattern
               (i.e., followed immediately by  another  -i)  is  made
               available  to  any  other  patterns in the same expect
               command associated with any_spawn_id.
               The -i flag may also name a global variable  in  which
               case  the  variable  is  read for a list of spawn ids.
               The variable is reread whenever it changes.  This pro-
               vides  a way of changing the I/O source while the com-
               mand is in execution.  Spawn ids provided this way are
               called "indirect" spawn ids.
               Actions such  as  break  and  continue  cause  control
               structures  (i.e.,  for,  proc) to behave in the usual
               way.  The command exp_continue allows expect itself to
               continue  executing  rather  than returning as it nor-
               mally would.
               This is useful for avoiding explicit loops or repeated
               expect statements.  The following example is part of a
               fragment to automate rlogin.  The exp_continue  avoids
               having to write a second expect statement (to look for
               the prompt again) if the rlogin prompts  for  a  pass-
                   expect {
                       Password: {
                           stty -echo
                           send_user "password (for $user) on $host: "
                           expect_user -re "(.*)\n"
                           send_user "\n"
                           send "$expect_out(1,string)\r"
                           stty echo
                       } incorrect {
                           send_user "invalid password or account\n"
                       } timeout {
                           send_user "connection to $host timed out\n"
                       } eof {
                           send_user \
                               "connection to host failed: $expect_out(buffer)"
                       } -re $prompt
               For example, the following fragment might help a  user
               guide   an   interaction   that   is  already  totally
               automated.  In this case, the terminal is put into raw
               mode.   If  the user presses "+", a variable is incre-
               mented.  If "p" is pressed, several returns  are  sent
               to  the  process,  perhaps to poke it in some way, and
               "i" lets the user interact with  the  process,  effec-
               tively stealing away control from the script.  In each
               case, the exp_continue allows the  current  expect  to
               continue  pattern matching after executing the current
                   stty raw -echo
                   expect_after {
                       -i $user_spawn_id
                       "p" {send "\r\r\r"; exp_continue}
                       "+" {incr foo; exp_continue}
                       "i" {interact; exp_continue}
                       "quit" exit
               By default, exp_continue  resets  the  timeout  timer.
               The  timer is not restarted, if exp_continue is called
               with the -continue_timer flag.
         expect_after [expect_args]
               works identically to the expect_before except that  if
               patterns  from both expect and expect_after can match,
               the expect pattern is  used.   See  the  expect_before
               command for more information.
         expect_background [expect_args]
               takes the same arguments as expect, however it returns
               immediately.   Patterns  are tested whenever new input
               arrives.  The pattern timeout and default are meaning-
               less  to expect_background and are silently discarded.
               Otherwise,   the   expect_background   command    uses
               expect_before  and  expect_after  patterns  just  like
               expect does.
               When expect_background actions  are  being  evaluated,
               background   processing  for  the  same  spawn  id  is
               blocked.  Background processing is unblocked when  the
               action  completes.   While  background  processing  is
               blocked, it is possible to do a (foreground) expect on
               the same spawn id.
               It is not possible  to  execute  an  expect  while  an
               expect_background is unblocked.  expect_background for
               a particular spawn id is deleted by  declaring  a  new
               expect_background  with  the same spawn id.  Declaring
               expect_background with no pattern  removes  the  given
               spawn  id  from  the  ability to match patterns in the
         expect_before [expect_args]
               takes the same arguments as expect, however it returns
               immediately.    Pattern-action  pairs  from  the  most
               recent expect_before with the same spawn id are impli-
               citly  added  to  any following expect commands.  If a
               pattern matches, it is  treated  as  if  it  had  been
               specified  in the expect command itself, and the asso-
               ciated body is executed in the context of  the  expect
               command.   If  patterns  from  both  expect_before and
               expect can match, the expect_before pattern is used.
               If no pattern  is  specified,  the  spawn  id  is  not
               checked for any patterns.
               Unless overridden by a -i flag, expect_before patterns
               match  against  the  spawn id defined at the time that
               the expect_before command was executed (not  when  its
               pattern is matched).
               The -info flag  causes  expect_before  to  return  the
               current specifications of what patterns it will match.
               By default, it reports on the current  spawn  id.   An
               optional  spawn  id  specification  may  be  given for
               information on that spawn id.  For example
                   expect_before -info -i $proc
               At most one spawn id specification may be given.   The
               flag  -indirect  suppresses direct spawn ids that come
               only from indirect specifications.
               Instead of a spawn id specification, the  flag  "-all"
               will cause "-info" to report on all spawn ids.
               The output of the -info flag  can  be  reused  as  the
               argument to expect_before.
         expect_tty [expect_args]
               is like expect but it reads characters  from  /dev/tty
               (i.e.  keystrokes from the user).  By default, reading
               is performed in cooked mode.   Thus,  lines  must  end
               with  a  return in order for expect to see them.  This
               may be changed via stty (see the stty command below).
         expect_user [expect_args]
               is like expect but  it  reads  characters  from  stdin
               (i.e.  keystrokes from the user).  By default, reading
               is performed in cooked mode.   Thus,  lines  must  end
               with  a  return in order for expect to see them.  This
               may be changed via stty (see the stty command below).
         fork  creates a new process.  The new process  is  an  exact
               copy  of the current Expect process.  On success, fork
               returns 0 to the new (child) process and  returns  the
               process ID of the child process to the parent process.
               On failure (invariably due to lack of resources, e.g.,
               swap  space,  memory),  fork  returns -1 to the parent
               process, and no child process is created.
               Forked processes exit via the exit command, just  like
               the original process.  Forked processes are allowed to
               write to the log files.  If you do not disable  debug-
               ging  or  logging in most of the processes, the result
               can be confusing.
               Some pty implementations may be confused  by  multiple
               readers  and  writers,  even momentarily.  Thus, it is
               safest to fork before spawning processes.
         interact [string1 body1] ... [stringn [bodyn]]
               gives control of the current process to the  user,  so
               that  keystrokes  are sent to the current process, and
               the stdout and  stderr  of  the  current  process  are
               String-body pairs may be specified  as  arguments,  in
               which case the body is executed when the corresponding
               string is entered.  (By default,  the  string  is  not
               sent  to  the current process.)   The interpreter com-
               mand is assumed, if the final body is missing.
               If the arguments  to  the  entire  interact  statement
               require  more  than one line, all the arguments may be
               "braced" into one so as to avoid terminating each line
               with  a  backslash.   In  this one case, the usual Tcl
               substitutions will occur despite the braces.
               For example, the following command runs interact  with
               the  following  string-body pairs defined:  When ^Z is
               pressed,  Expect  is  suspended.   (The  -reset   flag
               restores the terminal modes.)  When ^A is pressed, the
               user sees "you typed a control-A" and the  process  is
               sent a ^A.  When $ is pressed, the user sees the date.
               When  ^C  is  pressed,  Expect  exits.   If  "foo"  is
               entered, the user sees "bar".  When ~~ is pressed, the
               Expect interpreter runs interactively.
                   set CTRLZ \032
                   interact {
                       -reset $CTRLZ {exec kill -STOP [pid]}
                       \001   {send_user "you typed a control-A\n";
                               send "\001"
                       $      {send_user "The date is [exec date]."}
                       \003   exit
                       foo    {send_user "bar"}
               In string-body pairs, strings are matched in the order
               they  are listed as arguments.  Strings that partially
               match are not sent to the current process in anticipa-
               tion  of the remainder coming.  If characters are then
               entered such that there can no longer  possibly  be  a
               match, only the part of the string will be sent to the
               process that  cannot  possibly  begin  another  match.
               Thus,  strings  that are substrings of partial matches
               can match later, if  the  original  strings  that  was
               attempting to be match ultimately fails.
               By default, string matching  is  exact  with  no  wild
               cards.   (In  contrast,  the expect command uses glob-
               style patterns by default.)  The -ex flag may be  used
               to   protect   patterns  that  might  otherwise  match
               interact flags from doing so.  Any  pattern  beginning
               with  a  "-"  should  be  protected  this way.    (All
               strings starting with  "-"  are  reserved  for  future
               The -re flag forces the string to be interpreted as  a
               regexp-style  pattern.   In  this  case, matching sub-
               strings are stored in the variable interact_out  simi-
               larly to the way expect stores its output in the vari-
               able expect_out.  The -indices flag is similarly  sup-
               The pattern eof introduces an action that is  executed
               upon  end-of-file.   A  separate  eof pattern may also
               follow the -output flag in which case it is matched if
               an  eof is detected while writing output.  The default
               eof  action  is  "return",  so  that  interact  simply
               returns upon any EOF.
               The pattern timeout introduces a timeout (in  seconds)
               and  action  that is executed after no characters have
               been read for  a  given  time.   The  timeout  pattern
               applies to the most recently specified process.  There
               is no default timeout.  The special variable "timeout"
               (used  by  the  expect  command) has no affect on this
               For example, the following statement could be used  to
               autologout  users  who  have not typed anything for an
               hour but who still get frequent system messages:
                   interact -input $user_spawn_id timeout 3600 return -output \
               If the pattern is the  keyword  null,  and  nulls  are
               allowed    (via   the   remove_nulls   command),   the
               corresponding body is executed if a single ASCII 0  is
               matched.  It is not possible to match 0 bytes via glob
               or regexp patterns.
               Prefacing a pattern with the flag -iwrite  causes  the
               variable  interact_out(spawn_id)  to  be  set  to  the
               spawn_id which matched the pattern (or eof).
               Actions such  as  break  and  continue  cause  control
               structures  (i.e.,  for,  proc) to behave in the usual
               way.  However return causes interact to return to  its
               caller,  while inter_return causes interact to cause a
               return in its caller.   For  example,  if  "proc  foo"
               called   interact   which  then  executed  the  action
               inter_return, proc foo would return.  (This means that
               if  interact  calls  interpreter  interactively typing
               return will cause  the  interact  to  continue,  while
               inter_return  will cause the interact to return to its
               During interact, raw mode is used so that all  charac-
               ters  may  be  passed  to the current process.  If the
               current process does not catch job control signals, it
               will  stop  if sent a stop signal (by default ^Z).  To
               restart it, send a continue signal (such as  by  "kill
               -CONT  <pid>").   If you really want to send a SIGSTOP
               to such a process (by ^Z), consider spawning csh first
               and  then running your program.  On the other hand, if
               you want to send a SIGSTOP  to  Expect  itself,  first
               press the escape character, and then press ^Z.
               String-body pairs can  be  used  as  a  shorthand  for
               avoiding  having  to enter the interpreter and execute
               commands interactively.  The previous terminal mode is
               used  while  the  body  of a string-body pair is being
               For speed, actions execute in  raw  mode  by  default.
               The -reset flag resets the terminal to the mode it had
               before  interact  was  executed  (invariably,   cooked
               mode).   Note that characters entered when the mode is
               being switched may be lost (an unfortunate feature  of
               the terminal driver on some systems).  The only reason
               to use -reset is if your action depends on running  in
               cooked mode.
               The -echo flag sends characters that match the follow-
               ing pattern back to the process that generated them as
               each character is read.  This may be useful  when  the
               user  needs  to see feedback from partially typed pat-
               If a pattern is being echoed but eventually  fails  to
               match, the characters are sent to the spawned process.
               If the spawned process then echoes them, the user will
               see  the  characters  twice.   -echo  is probably only
               appropriate in situations where the user  is  unlikely
               to not complete the pattern.  For example, the follow-
               ing excerpt is from rftp,  the  recursive-ftp  script,
               where  the user is prompted to enter ~g, ~p, or ~l, to
               get, put, or list the current  directory  recursively.
               These  are  so  far away from the normal ftp commands,
               that the user is unlikely to type ~ followed  by  any-
               thing  else, except mistakenly, in which case, they'll
               probably just ignore the result anyway.
                   interact {
                       -echo ~g {getcurdirectory 1}
                       -echo ~l {getcurdirectory 0}
                       -echo ~p {putcurdirectory}
               The -nobuffer flag sends  characters  that  match  the
               following  pattern on to the output process as charac-
               ters are read.
               This is useful when you wish to  let  a  program  echo
               back the pattern.  For example, the following might be
               used to monitor where a person is  dialing  (a  Hayes-
               style modem).  Each time "atd" is seen the script logs
               the rest of the line.
                   proc lognumber {} {
                       interact -nobuffer -re "(.*)\r" return
                       puts $log "[exec date]: dialed $interact_out(1,string)"
                   interact -nobuffer "atd" lognumber
               During interact, previous use of log_user is  ignored.
               In  particular,  interact  will force its output to be
               logged (sent to  the  standard  output)  since  it  is
               presumed the user doesn't wish to interact blindly.
               The -o flag causes any following key-body pairs to  be
               applied  to  the  output of the current process.  This
               can be useful, for example, when  dealing  with  hosts
               that send unwanted characters during a telnet session.
               By default, interact expects the user  to  be  writing
               stdin and reading stdout of the Expect process itself.
               The -u flag (for "user") makes interact look  for  the
               user  as the process named by its argument (which must
               be a spawned id).
               This allows  two  unrelated  processes  to  be  joined
               together  without  using  an explicit loop.  To aid in
               debugging, Expect diagnostics always go to stderr  (or
               stdout for certain logging and debugging information).
               For the same reason, the interpreter command will read
               interactively from stdin.
               For example, the following fragment  creates  a  login
               process.   Then  it  dials  the  user (not shown), and
               finally connects the two  together.   Of  course,  any
               process  may  be  substituted for login.  A shell, for
               example,  would  allow  the  user  to   work   without
               supplying an account and password.
                   spawn login
                   set login $spawn_id
                   spawn tip modem
                   # dial back out to user
                   # connect user to login
                   interact -u $login
               To send output to multiple processes, list each  spawn
               id list prefaced by a -output flag.  Input for a group
               of output spawn ids may be determined by  a  spawn  id
               list  prefaced  by  a  -input  flag.  (Both -input and
               -output may take lists in the same form as the -i flag
               in the expect command, except that any_spawn_id is not
               meaningful in  interact.)   All  following  flags  and
               strings  (or  patterns)  apply  to  this  input  until
               another -input flag appears.  If  no  -input  appears,
               -output   implies   "-input  $user_spawn_id  -output".
               (Similarly, with patterns that do  not  have  -input.)
               If    one    -input   is   specified,   it   overrides
               $user_spawn_id.  If a second -input is  specified,  it
               overrides  $spawn_id.   Additional -input flags may be
               The two implied  input  processes  default  to  having
               their    outputs    specified    as    $spawn_id   and
               $user_spawn_id (in reverse). If a -input flag  appears
               with no -output flag, characters from that process are
               The -i flag introduces a replacement for  the  current
               spawn_id  when  no  other  -input or -output flags are
               used.  A -i flag implies a -o flag.
               It is possible to change the processes that are  being
               interacted   with   by   using   indirect  spawn  ids.
               (Indirect spawn ids are described in  the  section  on
               the expect command.)  Indirect spawn ids may be speci-
               fied with the -i, -u, -input, or -output flags.
               causes the  user  to  be  interactively  prompted  for
               Expect  and  Tcl commands.  The result of each command
               is printed.
               Actions such  as  break  and  continue  cause  control
               structures  (i.e.,  for,  proc) to behave in the usual
               way.  However return causes interpreter to  return  to
               its  caller,  while inter_return causes interpreter to
               cause a return in its caller.  For example,  if  "proc
               foo" called interpreter which then executed the action
               inter_return, proc foo would return.  Any  other  com-
               mand  causes interpreter to continue prompting for new
               By default, the prompt  contains  two  integers.   The
               first  integer  describes  the depth of the evaluation
               stack (i.e., how many times Tcl_Eval has been called).
               The second integer is the Tcl history identifier.  The
               prompt can be  set  by  defining  a  procedure  called
               "prompt1"  whose return value becomes the next prompt.
               If a statement has open  quotes,  parens,  braces,  or
               brackets,  a  secondary  prompt  (by default "+> ") is
               issued upon newline.  The secondary prompt may be  set
               by defining a procedure called "prompt2".
               During interpreter, cooked mode is used, even  if  the
               its caller was using raw mode.
         log_file [args] [[-a] file]
               If a filename is  provided,  log_file  will  record  a
               transcript of the session (beginning at that point) in
               the file.  log_file will stop recording if no argument
               is given.  Any previous log file is closed.
               Instead of a filename, a Tcl file  identifier  may  be
               provided by using the -open or -leaveopen flags.  This
               is similar to the spawn command.  (See spawn for  more
               The -a flag  forces  output  to  be  logged  that  was
               suppressed by the log_user command.
               By default, the log_file command appends to old  files
               rather  than  truncating  them, for the convenience of
               being able to turn logging off and on  multiple  times
               in  one session.  To truncate files, use the -noappend
               The -info flag causes log_file to return a description
               of the most recent non-info arguments given.
         log_user -info|0|1
               By default, the  send/expect  dialogue  is  logged  to
               stdout (and a logfile if open).  The logging to stdout
               is disabled by the command "log_user 0" and  reenabled
               by "log_user 1".  Logging to the logfile is unchanged.
               The -info flag causes log_user to return a description
               of the most recent non-info arguments given.
         match_max [-d] [-i spawn_id] [size]
               defines  the  size  of  the  buffer  (in  bytes)  used
               internally  by  expect.   With  no  size argument, the
               current size is returned.
               With the -d flag, the default size is set.  (The  ini-
               tial  default is 2000.)  With the -i flag, the size is
               set for the named spawn id, otherwise it  is  set  for
               the current process.
         overlay [-# spawn_id] [-# spawn_id] [...] program [args]
               executes program args in place of the  current  Expect
               program,  which  terminates.   A  bare hyphen argument
               forces a hyphen in front of the command name as if  it
               was  a  login  shell.  All spawn_ids are closed except
               for those named as arguments.  These are  mapped  onto
               the named file identifiers.
               Spawn_ids are mapped to file identifiers for  the  new
               program  to  inherit.  For example, the following line
               runs chess and allows  it  to  be  controlled  by  the
               current process - say, a chess master.
                   overlay -0 $spawn_id -1 $spawn_id -2 $spawn_id chess
               This is more efficient than "interact -u", however, it
               sacrifices  the  ability  to do programmed interaction
               since the Expect process is no longer in control.
               Note that no controlling terminal is provided.   Thus,
               if  you  disconnect  or remap standard input, programs
               that do job control  (shells,  login,  etc)  will  not
               function properly.
         parity [-d] [-i spawn_id] [value]
               defines whether parity should be retained or  stripped
               from  the  output  of  spawned processes.  If value is
               zero,  parity  is  stripped,  otherwise  it   is   not
               stripped.   With  no value argument, the current value
               is returned.
               With the -d flag, the default  parity  value  is  set.
               (The  initial  default  is  1,  i.e.,  parity  is  not
               stripped.)  With the -i flag, the parity value is  set
               for  the  named  spawn id, otherwise it is set for the
               current process.
         remove_nulls [-d] [-i spawn_id] [value]
               defines whether nulls are retained or removed from the
               output of spawned processes before pattern matching or
               storing in the variable  expect_out  or  interact_out.
               If  value  is  1,  nulls  are removed.  If value is 0,
               nulls are not removed.  With no  value  argument,  the
               current value is returned.
               With the -d flag, the default value is set.  (The ini-
               tial default is 1, i.e., nulls are removed.)  With the
               -i flag, the value is set for the named spawn id, oth-
               erwise it is set for the current process.
               Whether or not nulls are removed, Expect  will  record
               null bytes to the log and stdout.
         send [-flags] string
               Sends string to the current process.  For example, the
                   send "hello world\r"
               sends the characters, h e l l o <blank>  w  o  r  l  d
               <return>  to  the  current  process.  (Tcl  includes a
               printf-like command (called format)  which  can  build
               arbitrarily complex strings.)
               Characters are sent immediately although programs with
               line-buffered input will not read the characters until
               a return character is sent.   A  return  character  is
               denoted "\r".
               The -- flag forces the next argument to be interpreted
               as  a  string  rather  than a flag.  Any string can be
               preceded by "--" whether or not it actually looks like
               a flag.  This provides a reliable mechanism to specify
               variable strings without being  tripped  up  by  those
               that  accidentally  look  like  flags.   (All  strings
               starting with "-" are reserved for future options.)
               The -i flag declares that the string be  sent  to  the
               named spawn_id.  If the spawn_id is user_spawn_id, and
               the terminal is in raw mode, newlines  in  the  string
               are  translated  to  return-newline  sequences so that
               they appear as it the terminal  was  in  cooked  mode.
               The -raw flag disables this translation.
               The -null flag sends null characters  (0  bytes).   By
               default,  one null is sent.  An integer may follow the
               -null to indicate how many nulls to send.
               The -break flag generates  a  break  condition.   This
               only  makes sense if the spawn id refers to a tty dev-
               ice opened via "spawn -open".  If you have  spawned  a
               process  such  as tip, you should use tip's convention
               for generating a break.
               The -s flag forces output to be  sent  "slowly",  thus
               avoid  the  common situation where a computer outtypes
               an input buffer that was  designed  for  a  human  who
               would  never  outtype the same buffer.  This output is
               controlled by the value of  the  variable  "send_slow"
               which  takes a two element list.  The first element is
               an integer that describes the number of bytes to  send
               atomically.   The second element is a real number that
               describes the number of seconds by  which  the  atomic
               sends  must be separated.  For example, "set send_slow
               {10 .001}" would force "send -s" to send strings  with
               1 millisecond in between each 10 characters sent.
               The -h flag forces output to be sent (somewhat) like a
               human   actually  typing.   Human-like  delays  appear
               between the characters.  (The algorithm is based  upon
               a  Weibull  distribution,  with  modifications to suit
               this particular application.)   This  output  is  con-
               trolled  by  the  value  of  the variable "send_human"
               which takes a five element list.  The first  two  ele-
               ments  are  average interarrival time of characters in
               seconds.  The first is used by default.  The second is
               used  at  word  endings, to simulate the subtle pauses
               that occasionally  occur  at  such  transitions.   The
               third  parameter  is a measure of variability where .1
               is quite variable, 1 is reasonably variable, and 10 is
               quite  invariable.   The  extremes  are 0 to infinity.
               The last two parameters are, respectively,  a  minimum
               and  maximum  interarrival time.  The minimum and max-
               imum are used last and "clip"  the  final  time.   The
               ultimate average can be quite different from the given
               average if the minimum and maximum clip enough values.
               As an example, the following command emulates  a  fast
               and consistent typist:
                   set send_human {.1 .3 1 .05 2}
                   send -h "I'm hungry.  Let's do lunch."
               while the following might be  more  suitable  after  a
                   set send_human {.4 .4 .2 .5 100}
                   send -h "Goodd party lash night!"
               Note that errors are not simulated, although  you  can
               set  up error correction situations yourself by embed-
               ding mistakes and corrections in a send argument.
               The flags for sending  null  characters,  for  sending
               breaks,  for  forcing  slow output and for human-style
               output are mutually exclusive. Only the one  specified
               last will be used. Furthermore, no string argument can
               be specified with the flags for sending  null  charac-
               ters or breaks.
               It is a good idea to precede the first send to a  pro-
               cess  by  an expect.  expect will wait for the process
               to start, while send cannot.  In  particular,  if  the
               first  send  completes  before the process starts run-
               ning, you run the risk of having  your  data  ignored.
               In situations where interactive programs offer no ini-
               tial prompt, you can precede send by a delay as in:
                   # To avoid giving hackers hints on how to break in,
                   # this system does not prompt for an external password.
                   # Wait for 5 seconds for exec to complete
                   spawn telnet
                   sleep 5
                   send password\r
               exp_send is an alias  for  send.   If  you  are  using
               Expectk  or  some  other  variant  of Expect in the Tk
               environment, send is defined by  Tk  for  an  entirely
               different  purpose.  exp_send is provided for compati-
               bility between environments.  Similar aliases are pro-
               vided for other Expect's other send commands.
         send_error [-flags] string
               is like send, except that the output is sent to stderr
               rather than the current process.
         send_log [--] string
               is like send, except that the string is only  sent  to
               the  log  file  (see  log_file.)   The  arguments  are
               ignored if no log file is open.
         send_tty [-flags] string
               is like send,  except  that  the  output  is  sent  to
               /dev/tty rather than the current process.
         send_user [-flags] string
               is like send, except that the output is sent to stdout
               rather than the current process.
         sleep seconds
               causes the script to sleep for  the  given  number  of
               seconds.  Seconds may be a decimal number.  Interrupts
               (and Tk events if you are using Expectk) are processed
               while Expect sleeps.
         spawn [args] program [args]
               creates a  new  process  running  program  args.   Its
               stdin,  stdout  and stderr are connected to Expect, so
               that they may be read and written by other Expect com-
               mands.   The  connection  is broken by close or if the
               process itself closes any of the file identifiers.
               When a process  is  started  by  spawn,  the  variable
               spawn_id is set to a descriptor referring to that pro-
               cess.  The process described by spawn_id is considered
               the current process.  spawn_id may be read or written,
               in effect providing job control.
               user_spawn_id  is  a  global  variable  containing   a
               descriptor  which  refers  to  the user.  For example,
               when spawn_id is set to  this  value,  expect  behaves
               like expect_user.
               error_spawn_id  is  a  global  variable  containing  a
               descriptor  which  refers  to the standard error.  For
               example, when spawn_id is  set  to  this  value,  send
               behaves like send_error.
               tty_spawn_id  is  a  global  variable   containing   a
               descriptor which refers to /dev/tty.  If /dev/tty does
               not exist (such as in a cron, at,  or  batch  script),
               then  tty_spawn_id is not defined.  This may be tested
                   if {[info vars tty_spawn_id]} {
                       # /dev/tty exists
                   } else {
                       # /dev/tty doesn't exist
                       # probably in cron, batch, or at script
               spawn returns the UNIX process id.  If no  process  is
               spawned,     0     is    returned.     The    variable
               spawn_out(slave,name) is set to the name  of  the  pty
               slave device.
               By default, spawn echoes the command  name  and  argu-
               ments.  The -noecho flag stops spawn from doing this.
               The  -console  flag  causes  console  output   to   be
               redirected  to  the spawned process.  This is not sup-
               ported on all systems.
               Internally, spawn uses a pty, initialized the same way
               as  the  user's  tty.   This is further initialized so
               that all settings are "sane" (according  to  stty(1)).
               If  the  variable  stty_init  is defined, it is inter-
               preted in the style of stty arguments as further  con-
               figuration.   For  example,  "set  stty_init raw" will
               cause further spawned processes's terminals  to  start
               in  raw  mode.   -nottycopy  skips  the initialization
               based on the user's tty.  -nottyinit skips the  "sane"
               Normally, spawn takes little time to execute.  If  you
               notice  spawn  taking a significant amount of time, it
               is probably encountering  ptys  that  are  wedged.   A
               number of tests are run on ptys to avoid entanglements
               with errant processes.  (These  take  10  seconds  per
               wedged  pty.)   Running Expect with the -d option will
               show if  Expect  is  encountering  many  ptys  in  odd
               states.   If  you  cannot  kill the processes to which
               these ptys are attached, your only recourse may be  to
               If program  cannot  be  spawned  successfully  because
               exec(2)  fails  (e.g.  when program doesn't exist), an
               error message will be returned by the next interact or
               expect  command as if program had run and produced the
               error message as output.  This behavior is  a  natural
               consequence  of  the  implementation of spawn.  Inter-
               nally, spawn forks, after which  the  spawned  process
               has  no  way  to  communicate with the original Expect
               process except by communication via the spawn_id.
               The -open flag causes the next argument to  be  inter-
               preted  as  a  Tcl  file identifier (i.e., returned by
               open.)  The spawn id can then be used as if it were  a
               spawned  process.   (The  file  identifier  should  no
               longer be used.)  This lets  you  treat  raw  devices,
               files,  and  pipelines  as  spawned  processes without
               using a pty.  0 is returned to indicate  there  is  no
               associated   process.   When  the  connection  to  the
               spawned process is closed, so is the Tcl file identif-
               ier.   The  -leaveopen flag is similar to -open except
               that -leaveopen causes the file identifier to be  left
               open even after the spawn id is closed.
               The -pty flag causes a pty to be opened but no process
               spawned.   0 is returned to indicate there is no asso-
               ciated process.  Spawn_id is set as usual.
               The variable spawn_out(slave,fd)  is  set  to  a  file
               identifier  corresponding to the pty slave.  It can be
               closed using "close -slave".
               The -ignore flag names a signal to be ignored  in  the
               spawned  process.   Otherwise, signals get the default
               behavior.  Signals are named as in the  trap  command,
               except that each signal requires a separate flag.
         strace level
               causes following statements to be printed before being
               executed.   (Tcl's  trace  command  traces variables.)
               level indicates how far down  in  the  call  stack  to
               trace.  For example, the following command runs Expect
               while tracing the first 4 levels of  calls,  but  none
               below that.
                   expect -c "strace 4" script.exp
               The -info flag causes strace to return  a  description
               of the most recent non-info arguments given.
         stty args
               changes terminal modes similarly to the external  stty
               By default,  the  controlling  terminal  is  accessed.
               Other  terminals  can  be  accessed  by  appending  "<
               /dev/tty..." to the command.  (Note that the arguments
               should not be grouped into a single argument.)
               Requests for status return it as  the  result  of  the
               command.   If  no status is requested and the control-
               ling terminal is accessed, the previous status of  the
               raw  and  echo attributes are returned in a form which
               can later be used by the command.
               For example, the arguments raw or -cooked put the ter-
               minal into raw mode.  The arguments -raw or cooked put
               the terminal into cooked mode.  The arguments echo and
               -echo  put  the  terminal  into  echo  and noecho mode
               The following example illustrates how  to  temporarily
               disable  echoing.   This  could  be used in otherwise-
               automatic scripts  to  avoid  embedding  passwords  in
               them.  (See more discussion on this under EXPECT HINTS
                   stty -echo
                   send_user "Password: "
                   expect_user -re "(.*)\n"
                   set password $expect_out(1,string)
                   stty echo
         system args
               gives args to sh(1) as input, just as if it  had  been
               typed  as  a  command  from  a terminal.  Expect waits
               until the shell terminates.  The return status from sh
               is  handled  the same way that exec handles its return
               In contrast to exec which redirects stdin  and  stdout
               to  the  script, system performs no redirection (other
               than that indicated by the string itself).   Thus,  it
               is  possible  to use programs which must talk directly
               to /dev/tty.  For the same reason, the results of sys-
               tem are not recorded in the log.
         timestamp [args]
               returns a timestamp.  With no arguments, the number of
               seconds since the epoch is returned.
               The -format flag introduces a string which is returned
               but  with  substitutions  made  according to the POSIX
               rules for strftime.  For example %a is replaced by  an
               abbreviated weekday name (i.e., Sat).  Others are:
                   %a      abbreviated weekday name
                   %A      full weekday name
                   %b      abbreviated month name
                   %B      full month name
                   %c      date-time as in: Wed Oct  6 11:45:56 1993
                   %d      day of the month (01-31)
                   %H      hour (00-23)
                   %I      hour (01-12)
                   %j      day (001-366)
                   %m      month (01-12)
                   %M      minute (00-59)
                   %p      am or pm
                   %S      second (00-61)
                   %u      day (1-7, Monday is first day of week)
                   %U      week (00-53, first Sunday is first day of week one)
                   %V      week (01-53, ISO 8601 style)
                   %w      day (0-6)
                   %W      week (00-53, first Monday is first day of week one)
                   %x      date-time as in: Wed Oct  6 1993
                   %X      time as in: 23:59:59
                   %y      year (00-99)
                   %Y      year as in: 1993
                   %Z      timezone (or nothing if not determinable)
                   %%      a bare percent sign
               Other % specifications are undefined.   Other  charac-
               ters  will  be  passed  through untouched.  Only the C
               locale is supported.
               The -seconds flag introduces a number of seconds since
               the epoch to be used as a source from which to format.
               Otherwise, the current time is used.
               The -gmt flag forces timestamp output to use  the  GMT
               timezone.  With no flag, the local timezone is used.
         trap [[command] signals]
               causes the given command to be  executed  upon  future
               receipt  of  any of the given signals.  The command is
               executed in the global scope.  If command  is  absent,
               the  signal  action  is  returned.   If command is the
               string SIG_IGN, the signals are ignored.   If  command
               is  the  string SIG_DFL, the signals are result to the
               system default.  signals is either a single signal  or
               a  list  of signals.  Signals may be specified numeri-
               cally or symbolically as  per  signal(3).   The  "SIG"
               prefix may be omitted.
               With no arguments  (or  the  argument  -number),  trap
               returns   the   signal  number  of  the  trap  command
               currently being executed.
               The -code flag uses the return code of the command  in
               place  of  whatever  code Tcl was about to return when
               the command originally started running.
               The -interp flag causes the command  to  be  evaluated
               using  the  interpreter active at the time the command
               started  running  rather  than  when  the   trap   was
               The -name flag causes the trap command to  return  the
               signal  name  of the trap command currently being exe-
               The -max flag causes the trap command  to  return  the
               largest signal number that can be set.
               For example, the  command  "trap  {send_user  "Ouch!"}
               SIGINT" will print "Ouch!"  each time the user presses
               By default, SIGINT (which can usually be generated  by
               pressing  ^C)  and SIGTERM cause Expect to exit.  This
               is due to the following trap, created by default  when
               Expect starts.
                   trap exit {SIGINT SIGTERM}
               If you use the -D flag to start the  debugger,  SIGINT
               is  redefined to start the interactive debugger.  This
               is due to the following trap:
                   trap {exp_debug 1} SIGINT
               The debugger  trap  can  be  changed  by  setting  the
               environment  variable  EXPECT_DEBUG_INIT to a new trap
               You can, of course, override both  of  these  just  by
               adding  trap  commands to your script.  In particular,
               if you have your own "trap  exit  SIGINT",  this  will
               override  the  debugger  trap.   This is useful if you
               want to prevent users from getting to the debugger  at
               If you want to define your  own  trap  on  SIGINT  but
               still trap to the debugger when it is running, use:
                   if ![exp_debug] {trap mystuff SIGINT}
               Alternatively, you can trap to the debugger using some
               other signal.
               trap will not let you override the action for  SIGALRM
               as  this is used internally to Expect.  The disconnect
               command sets SIGALRM to  SIG_IGN  (ignore).   You  can
               reenable  this as long as you disable it during subse-
               quent spawn commands.
               See signal(3) for more info.
         wait [args]
               delays until a spawned process (or the current process
               if none is named) terminates.
               wait normally returns a list of  four  integers.   The
               first  integer  is  the  pid  of  the process that was
               waited upon.  The second integer is the  corresponding
               spawn  id.   The  third  integer is -1 if an operating
               system error occurred, or 0 otherwise.  If  the  third
               integer  was  0,  the  fourth  integer  is  the status
               returned by the spawned process.  If the third integer
               was  -1,  the fourth integer is the value of errno set
               by the operating system.  The global  variable  error-
               Code is also set.
               Additional elements may  appear  at  the  end  of  the
               return  value  from  wait.   An optional fifth element
               identifies a class  of  information.   Currently,  the
               only possible value for this element is CHILDKILLED in
               which case the next two values are the C-style  signal
               name and a short textual description.
               The -i flag declares the process to wait corresponding
               to  the named spawn_id (NOT the process id).  Inside a
               SIGCHLD handler,  it  is  possible  to  wait  for  any
               spawned process by using the spawn id -1.
               The -nowait flag causes the wait to return immediately
               with  the  indication  of a successful wait.  When the
               process exits (later), it will automatically disappear
               without the need for an explicit wait.
               The wait command may also be used wait  for  a  forked
               process  using  the arguments "-i -1".  Unlike its use
               with spawned processes, this command can  be  executed
               at  any  time.  There is no control over which process
               is reaped.  However, the return value can  be  checked
               for the process id.
         Expect automatically knows about two built-in libraries  for
         Expect  scripts.  These are defined by the directories named
         in the variables exp_library and exp_exec_library.  Both are
         meant  to  contain  utility  files that can be used by other
         exp_library   contains    architecture-independent    files.
         exp_exec_library   contains   architecture-dependent  files.
         Depending on your system, both directories  may  be  totally
         empty.   The  existence  of  the file $exp_exec_library/cat-
         buffers describes whether your /bin/cat buffers by default.
         A vgrind definition is available for pretty-printing  Expect
         scripts.   Assuming  the vgrind definition supplied with the
         Expect distribution is correctly installed, you can  use  it
             vgrind -lexpect file
         It many not be apparent how to put everything together  that
         the man page describes.  I encourage you to read and try out
         the examples in the example directory of the Expect  distri-
         bution.   Some of them are real programs.  Others are simply
         illustrative of certain techniques, and of course, a  couple
         are just quick hacks.  The INSTALL file has a quick overview
         of these programs.
         The Expect papers (see SEE ALSO)  are  also  useful.   While
         some  papers use syntax corresponding to earlier versions of
         Expect, the accompanying rationales are still valid  and  go
         into a lot more detail than this man page.
         Extensions may collide with  Expect's  command  names.   For
         example,  send  is  defined  by Tk for an entirely different
         purpose.  For this reason, most of the Expect  commands  are
         also available as "exp_XXXX".  Commands and variables begin-
         ning with "exp", "inter", "spawn", and "timeout" do not have
         aliases.   Use  the  extended command names if you need this
         compatibility between environments.
         Expect takes a rather liberal view of scoping.  In  particu-
         lar,  variables read by commands specific to the Expect pro-
         gram will be sought first from the local scope, and  if  not
         found,  in the global scope.  For example, this obviates the
         need to place "global timeout" in every procedure you  write
         that  uses expect.  On the other hand, variables written are
         always in the local scope (unless  a  "global"  command  has
         been  issued).   The most common problem this causes is when
         spawn is executed in a procedure.   Outside  the  procedure,
         spawn_id  no  longer  exists,  so  the spawned process is no
         longer accessible simply because of scoping.  Add a  "global
         spawn_id" to such a procedure.
         If you cannot enable  the  multispawning  capability  (i.e.,
         your system supports neither select (BSD *.*), poll (SVR>2),
         nor something equivalent), Expect will only be able to  con-
         trol  a  single  process  at  a  time.  In this case, do not
         attempt to set spawn_id, nor should  you  execute  processes
         via  exec  while a spawned process is running.  Furthermore,
         you will not be  able  to  expect  from  multiple  processes
         (including the user as one) at the same time.
         Terminal parameters can have a big effect on  scripts.   For
         example, if a script is written to look for echoing, it will
         misbehave if echoing is turned off.  For this reason, Expect
         forces  sane terminal parameters by default.  Unfortunately,
         this can make things unpleasant for other programs.   As  an
         example,  the  emacs  shell wants to change the "usual" map-
         pings: newlines get mapped to newlines instead of  carriage-
         return  newlines,  and echoing is disabled.  This allows one
         to use emacs to edit the input line.  Unfortunately,  Expect
         cannot possibly guess this.
         You can request that Expect not override its default setting
         of  terminal  parameters,  but you must then be very careful
         when writing scripts for such environments.  In the case  of
         emacs,  avoid depending upon things like echoing and end-of-
         line mappings.
         The commands that accepted arguments braced  into  a  single
         list  (the  expect variants and interact) use a heuristic to
         decide if the list is actually one argument  or  many.   The
         heuristic  can  fail only in the case when the list actually
         does represent a single argument which has multiple embedded
         \n's  with  non-whitespace  characters  between  them.  This
         seems  sufficiently   improbable,   however   the   argument
         "-nobrace" can be used to force a single argument to be han-
         dled as a single argument.  This could conceivably  be  used
         with machine-generated Expect code.
         It was really tempting to name the program "sex" (for either
         "Smart  EXec"  or "Send-EXpect"), but good sense (or perhaps
         just Puritanism) prevailed.
         On some systems, when a shell is spawned, it complains about
         not  being  able  to  access  the tty but runs anyway.  This
         means your system has a mechanism for gaining  the  control-
         ling  tty  that  Expect doesn't know about.  Please find out
         what it is, and send this information back to me.
         Ultrix 4.1 (at least the latest versions around  here)  con-
         siders timeouts of above 1000000 to be equivalent to 0.
         Digital UNIX 4.0A (and probably other versions)  refuses  to
         allocate  ptys if you define a SIGCHLD handler.  See grantpt
         page for more info.
         IRIX 6.0 does not handle pty permissions correctly  so  that
         if  Expect  attempts  to  allocate  a pty previously used by
         someone else, it fails.  Upgrade to IRIX 6.1.
         Telnet (verified only under SunOS 4.1.2) hangs  if  TERM  is
         not  set.   This  is  a  problem  under  cron, at and in cgi
         scripts, which do not define TERM.  Thus, you  must  set  it
         explicitly  -  to  what type is usually irrelevant.  It just
         has to be set to something!  The following probably suffices
         for most cases.
             set env(TERM) vt100
         Tip (verified only under BSDI  BSD/OS  3.1  i386)  hangs  if
         SHELL  and  HOME are not set.  This is a problem under cron,
         at and in cgi scripts, which do not define these environment
         variables.   Thus,  you  must  set them explicitly - to what
         type is usually irrelevant.  It just has to be set to  some-
         thing!  The following probably suffices for most cases.
             set env(SHELL) /bin/sh
             set env(HOME) /usr/local/bin
         Some implementations of ptys are designed so that the kernel
         throws away any unread output after 10 to 15 seconds (actual
         number is implementation-dependent) after  the  process  has
         closed the file descriptor.  Thus Expect programs such as
             spawn date
             sleep 20
         will fail.  To avoid this, invoke  non-interactive  programs
         with exec rather than spawn.  While such situations are con-
         ceivable, in practice I have never encountered  a  situation
         in  which  the  final  output of a truly interactive program
         would be lost due to this behavior.
         On the other hand, Cray UNICOS ptys throw  away  any  unread
         output  immediately  after  the  process has closed the file
         descriptor.  I have reported this to Cray and they are work-
         ing on a fix.
         Sometimes a  delay  is  required  between  a  prompt  and  a
         response, such as when a tty interface is changing UART set-
         tings or matching baud rates by looking for start/stop bits.
         Usually,  all  this  is  require is to sleep for a second or
         two.  A more robust technique is to retry until the hardware
         is  ready to receive input.  The following example uses both
             send "speed 9600\r";
             sleep 1
             expect {
                 timeout {send "\r"; exp_continue}
         There are a couple of things about Expect that may  be  non-
         intuitive.   This  section attempts to address some of these
         things with a couple of suggestions.
         A common expect problem is how to recognize  shell  prompts.
         Since these are customized differently by differently people
         and different shells, portably automating rlogin can be dif-
         ficult  without knowing the prompt.  A reasonable convention
         is to have users store a regular expression describing their
         prompt  (in  particular,  the  end of it) in the environment
         variable EXPECT_PROMPT.  Code  like  the  following  can  be
         used.   If EXPECT_PROMPT doesn't exist, the code still has a
         good chance of functioning correctly.
             set prompt "(%|#|\\$) $"          ;# default prompt
             catch {set prompt $env(EXPECT_PROMPT)}
             expect -re $prompt
         I encourage you to write expect patterns  that  include  the
         end  of  whatever you expect to see.  This avoids the possi-
         bility of answering a  question  before  seeing  the  entire
         thing.   In  addition,  while you may well be able to answer
         questions before seeing them entirely, if you answer  early,
         your  answer  may  appear  echoed  back in the middle of the
         question.  In other words, the resulting  dialogue  will  be
         correct but look scrambled.
         Most prompts include a space  character  at  the  end.   For
         example,  the  prompt  from  ftp  is  'f', 't', 'p', '>' and
         <blank>.  To match this prompt, you must account for each of
         these characters.  It is a common mistake not to include the
         blank.  Put the blank in explicitly.
         If you use a pattern of the form X*, the *  will  match  all
         the  output  received  from  the  end of X to the last thing
         received.  This sounds intuitive but can be somewhat confus-
         ing  because  the  phrase  "last  thing  received"  can vary
         depending upon the speed of the computer and the  processing
         of I/O both by the kernel and the device driver.
         In particular, humans tend to see program output arriving in
         huge  chunks (atomically) when in reality most programs pro-
         duce output one line at a time.  Assuming this is the  case,
         the  *  in  the  pattern  of the previous paragraph may only
         match the end of the current line even though there seems to
         be  more,  because at the time of the match that was all the
         output that had been received.
         expect has no way of knowing that further output  is  coming
         unless your pattern specifically accounts for it.
         Even depending on line-oriented buffering  is  unwise.   Not
         only  do  programs  rarely  make  promises about the type of
         buffering they do, but system indigestion can  break  output
         lines  up  so  that  lines break at seemingly random places.
         Thus, if you can express the last few characters of a prompt
         when writing patterns, it is wise to do so.
         If you are waiting for a pattern in the  last  output  of  a
         program  and  the  program emits something else instead, you
         will not be able to detect that with  the  timeout  keyword.
         The reason is that expect will not timeout - instead it will
         get an eof indication.  Use that instead.  Even better,  use
         both.  That way if that line is ever moved around, you won't
         have to edit the line itself.
         Newlines are usually converted to carriage return,  linefeed
         sequences  when output by the terminal driver.  Thus, if you
         want a pattern that explicitly matches the two lines,  from,
         say,   printf("foo\nbar"),   you   should  use  the  pattern
         A similar translation occurs when reading from the user, via
         expect_user.   In  this case, when you press return, it will
         be translated to a newline.  If Expect then passes that to a
         program  which  sets its terminal to raw mode (like telnet),
         there is going to be a problem, as  the  program  expects  a
         true  return.  (Some programs are actually forgiving in that
         they will automatically translate newlines to  returns,  but
         most  don't.)   Unfortunately,  there  is no way to find out
         that a program put its terminal into raw mode.
         Rather than manually replacing newlines  with  returns,  the
         solution  is  to use the command "stty raw", which will stop
         the translation.  Note, however, that this  means  that  you
         will no longer get the cooked line-editing features.
         interact implicitly sets your terminal to raw mode  so  this
         problem will not arise then.
         It is often useful to  store  passwords  (or  other  private
         information)  in  Expect  scripts.   This is not recommended
         since anything that is stored on a computer  is  susceptible
         to  being accessed by anyone.  Thus, interactively prompting
         for passwords from a script is a smarter idea than embedding
         them  literally.   Nonetheless,  sometimes such embedding is
         the only possibility.
         Unfortunately, the UNIX file system has  no  direct  way  of
         creating  scripts which are executable but unreadable.  Sys-
         tems which support setgid shell scripts may indirectly simu-
         late this as follows:
         Create the Expect script (that contains the secret data)  as
         usual.   Make  its permissions be 750 (-rwxr-x---) and owned
         by a trusted group, i.e., a group which is allowed  to  read
         it.   If  necessary,  create  a  new group for this purpose.
         Next,  create  a  /bin/sh  script  with   permissions   2751
         (-rwxr-s--x) owned by the same group as before.
         The result is a script which may be executed (and  read)  by
         anyone.  When invoked, it runs the Expect script.
         Tcl(3), libexpect(3)
         "Exploring  Expect:  A  Tcl-Based  Toolkit  for   Automating
         Interactive  Programs"  by Don Libes, pp. 602, ISBN 1-56592-
         090-2, O'Reilly and Associates, 1995.
         "expect: Curing Those Uncontrollable Fits of  Interactivity"
         by  Don Libes, Proceedings of the Summer 1990 USENIX Confer-
         ence, Anaheim, California, June 11-15, 1990.
         "Using expect to Automate System  Administration  Tasks"  by
         Don Libes, Proceedings of the 1990 USENIX Large Installation
         Systems   Administration   Conference,   Colorado   Springs,
         Colorado, October 17-19, 1990.
         "Tcl: An Embeddable Command Language"  by  John  Ousterhout,
         Proceedings   of   the   Winter   1990   USENIX  Conference,
         Washington, D.C., January 22-26, 1990.
         "expect: Scripts for Controlling  Interactive  Programs"  by
         Don  Libes,  Computing Systems, Vol. 4, No. 2, University of
         California Press Journals, November 1991.
         "Regression Testing and Conformance Testing Interactive Pro-
         grams",  by Don Libes, Proceedings of the Summer 1992 USENIX
         Conference, pp. 135-144, San Antonio, TX, June 12-15, 1992.
         "Kibitz   -   Connecting   Multiple   Interactive   Programs
         Together",  by  Don Libes, Software - Practice & Experience,
         John Wiley & Sons, West Sussex, England,  Vol.  23,  No.  5,
         May, 1993.
         "A Debugger for Tcl Applications", by Don Libes, Proceedings
         of the 1993 Tcl/Tk Workshop, Berkeley, CA, June 10-11, 1993.
         Don Libes, National Institute of Standards and Technology
         Thanks to John Ousterhout for Tcl,  and  Scott  Paisley  for
         inspiration.   Thanks  to Rob Savoye for Expect's autoconfi-
         guration code.
         The HISTORY file documents much of the evolution of  expect.
         It  makes  interesting  reading  and  might give you further
         insight to this software.  Thanks to the people mentioned in
         it who sent me bug fixes and gave other assistance.
         Design and implementation of Expect was paid for in part  by
         the  U.S.  government and is therefore in the public domain.
         However the author and NIST would like credit if  this  pro-
         gram and documentation or portions of them are used.

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