EXPECT(1) EXPECT(1)
expect - programmed dialogue with interactive programs, Version 5
expect [ -dDinN ] [ -c cmds ] [ -fb ] cmdfile ] [ args ]
Expect is a program that "talks" to other interactive programs according
to a script. Following the script, Expect knows what can be expected
from a program and what the correct response should be. An interpreted
language provides branching and high-level control structures to direct
the dialogue. In addition, the user can take control and interact
directly when desired, afterward returning control to the script.
Expectk is a mixture of Expect and Tk. It behaves just like Expect and
Tk's wish. Expect can also be used directly in C or C++ (that is,
without Tcl). See libexpect(3).
The name "Expect" comes from the idea of send/expect sequences
popularized by uucp, kermit and other modem control programs. However
unlike uucp, Expect is generalized so that it can be run as a user-level
command with any program and task in mind. Expect can actually talk to
several programs at the same time.
For example, here are some things Expect can do:
o Cause your computer to dial you back, so that you can login
without paying for the call.
o Start a game (e.g., rogue) and if the optimal configuration
doesn't appear, restart it (again and again) until it does, then
hand over control to you.
o Run fsck, and in response to its questions, answer "yes", "no"
or give control back to you, based on predetermined criteria.
o Connect to another network or BBS (e.g., MCI Mail, CompuServe)
and automatically retrieve your mail so that it appears as if it
was originally sent to your local system.
o Carry environment variables, current directory, or any kind of
information across rlogin, telnet, tip, su, chgrp, etc.
There are a variety of reasons why the shell cannot perform these tasks.
(Try, you'll see.) All are possible with Expect.
In general, Expect is useful for running any program which requires
interaction between the program and the user. All that is necessary is
that the interaction can be characterized programmatically. Expect 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.
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Expect reads cmdfile for a list of commands to execute. Expect may also
be invoked implicitly on systems which support the #! notation by marking
the script executable, and making the first line in your script:
#! /usr/sgitcl/bin/expect -f
Of course, the path must accurately describe where Expect lives,
/usr/sgitcl/bin on IRIX systems.
The -c flag prefaces a command to be executed before any in the script.
The command should be quoted to prevent being broken up by the shell.
This option may be used multiple times. Multiple commands may be
executed with a single -c by separating them with semicolons. Commands
are executed in the order they appear. (When using Expectk, this option
is specified as -command.)
The -d flag enables some diagnostic output, which primarily reports
internal activity of commands such as expect and interact. This flag has
the same effect as "exp_internal 1" at the beginning of an Expect script,
plus the version of Expect is printed. (The strace command is useful for
tracing statements, and the trace command is useful for tracing variable
assignments.) (When using Expectk, this option is specified as -diag.)
The -D flag enables an interactive debugger. An integer value should
follow. The debugger will take control before the next Tcl procedure if
the value is non-zero or if a ^C is pressed (or a breakpoint is hit, or
other appropriate debugger command appears in the script). See the
README file or SEE ALSO (below) for more information on the debugger.
(When using Expectk, this option is specified as -Debug.)
The -f flag prefaces a file from which to read commands from. The flag
itself is optional as it is only useful when using the #! notation (see
above), so that other arguments may be supplied on the command line.
(When using Expectk, this option is specified as -file.)
By default, the command file is read into memory and executed in its
entirety. It is occasionally desirable to read files one line at a time.
For example, stdin is read this way. In order to force arbitrary files
to be handled this way, use the -b flag. (When using Expectk, this
option is specified as -buffer.)
If the string "-" is supplied as a filename, standard input is read
instead. (Use "./-" to read from a file actually named "-".)
The -i flag causes Expect to interactively prompt for commands instead of
reading them from a file. Prompting is terminated via the exit command
or upon EOF. See interpreter (below) for more information. -i is
assumed if neither a command file nor -c is used. (When using Expectk,
this option is specified as -interactive.)
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-- 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/sgitcl/bin/expect --
Note that the usual getopt(3) and execve(2) conventions must be observed
when adding arguments to the #! line.
The file $exp_library/expect.rc is sourced automatically if present,
unless the -N flag is used. (When using Expectk, this option is specified
as -NORC.) Immediately after this, the file ~/.expect.rc is sourced
automatically, unless the -n flag is used. If the environment variable
DOTDIR is defined, it is treated as a directory and .expect.rc is read
from there. (When using Expectk, this option is specified as -norc.)
This sourcing occurs only after executing any -c flags.
Optional args are constructed into a list and stored in the variable
named argv. argc is initialized to the length of argv.
argv0 is defined to be the name of the script (or binary if no script is
used). For example, the following prints out the name of the script and
the first three arguments:
send_user "$argv0 [lrange $argv 0 2]\n"
Expect uses Tcl (Tool Command Language). Tcl provides control flow
(e.g., if, for, break), expression evaluation and several other features
such as recursion, procedure definition, etc. Commands used here but not
defined (e.g., set, if, exec) are Tcl commands (see tcl(3)). Expect
supports additional commands, described below. Unless otherwise
specified, commands return the empty string.
Commands are listed alphabetically so that they can be quickly located.
However, new users may find it easier to start by reading the
descriptions of spawn, send, expect, and interact, in that order.
Note that the best introduction to the language (both Expect and Tcl) is
provided in the book "Exploring Expect" (see SEE ALSO below). Examples
are included in this man page but they are very limited since this man
page is meant primarily as reference material.
Note that in the text of this man page, "Expect" with an uppercase "E"
refers to the Expect program while "expect" with a lower-case "e" refers
to the expect command within the Expect program.)
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close [-slave] [-onexec 0|1] [-i spawn_id]
closes the connection to the current process. Most interactive
programs will detect EOF on their stdin and exit; thus close
usually suffices to kill the process as well. The -i flag
declares the process to close corresponding to the named
spawn_id.
Both expect and interact will detect when the current process
exits and implicitly do a close. But if you kill the process
by, say, "exec kill $pid", you will need to explicitly call
close.
The -onexec flag determines whether the spawn id will be closed
in any new spawned processes or if the process is overlayed.
To leave a spawn id open, use the value 0. A non-zero integer
value will force the spawn closed (the default) in any new
processes.
The -slave flag closes the slave associated with the spawn id.
(See "spawn -pty".) When the connection is closed, the slave
is automatically closed as well if still open.
No matter whether the connection is closed implicitly or
explicitly, you should call wait to clear up the corresponding
kernel process slot. close does not call wait since there is
no guarantee that closing a process connection will cause it to
exit. See wait below for more info.
debug [[-now] 0|1]
controls a Tcl debugger allowing you to step through
statements, set breakpoints, etc.
With no arguments, a 1 is returned if the debugger is not
running, otherwise a 0 is returned.
With a 1 argument, the debugger is started. With a 0 argument,
the debugger is stopped. If a 1 argument is preceded by the
-now flag, the debugger is started immediately (i.e., in the
middle of the debug command itself). Otherwise, the debugger
is started with the next Tcl statement.
The debug command does not change any traps. Compare this to
starting Expect with the -D flag (see above).
See the README file or SEE ALSO (below) for more information on
the debugger.
disconnect
disconnects a forked process from the terminal. It continues
running in the background. The process is given its own
process group (if possible). Standard I/O is redirected to
/dev/null.
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The following fragment uses disconnect to continue running the
script in the background.
if [fork]!=0 exit
disconnect
. . .
The following script reads a password, and then runs a program
every hour that demands a password each time it is run. The
script supplies the password so that you only have to type it
once. (See the stty command which demonstrates how to turn off
password echoing.)
send_user "password?\ "
expect_user -re "(.*)\n"
for {} 1 {} {
if [fork]!=0 {sleep 3600;continue}
disconnect
spawn priv_prog
expect Password:
send "$expect_out(1,string)\r"
. . .
exit
}
An advantage to using disconnect over the shell asynchronous
process feature (&) is that Expect can save the terminal
parameters prior to disconnection, and then later apply them to
new ptys. With &, Expect does not have a chance to read the
terminal's parameters since the terminal is already
disconnected by the time Expect receives control.
exit [-opts] [status]
causes Expect to exit or otherwise prepare to do so.
The -onexit flag causes the next argument to be used as an exit
handler. Without an argument, the current exit handler is
returned.
The -noexit flag causes Expect to prepare to exit but stop
short of actually returning control to the operating system.
The user-defined exit handler is run as well as Expect's own
internal handlers. No further Expect commands should be
executed. This is useful if you are running Expect with other
Tcl extensions. The current interpreter (and main window if in
the Tk environment) remain so that other Tcl extensions can
clean up. If Expect's exit is called again (however this might
occur), the handlers are not rerun.
Upon exiting, all connections to spawned processes are closed.
Closure will be detected as an EOF by spawned processes. exit
takes no other actions beyond what the normal _exit(2)
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procedure does. Thus, spawned processes that do not check for
EOF may continue to run. (A variety of conditions are
important to determining, for example, what signals a spawned
process will be sent, but these are system-dependent, typically
documented under exit(3).) Spawned processes that continue to
run will be inherited by init.
status (or 0 if not specified) is returned as the exit status
of Expect. exit is implicitly executed if the end of the
script is reached.
exp_continue
The command exp_continue allows expect itself to continue
executing rather than returning as it normally would. (See
expect for more information.)
exp_open [args] [-i spawn_id]
returns a Tcl file identifier that corresponds to the original
spawn id. The file identifier can then be used as if it were
opened by Tcl's open command. (The spawn id should no longer
be used. A wait should not be executed.
The -leaveopen flag leaves the spawn id open for access through
Expect commands. A wait must be executed on the spawn id.
exp_pid [-i spawn_id]
returns the process id corresponding to the currently spawned
process. If the -i flag is used, the pid returned corresponds
to that of the given spawn id.
expect [[-opts] pat1 body1] ... [-opts] patn [bodyn]
waits until one of the patterns matches the output of a spawned
process, a specified time period has passed, or an end-of-file
is seen. If the final body is empty, it may be omitted.
Patterns from the most recent expect_before command are
implicitly used before any other patterns. Patterns from the
most recent expect_after command are implicitly used after any
other patterns.
If the arguments to the entire expect statement require more
than one line, all the arguments may be "braced" into one so as
to avoid terminating each line with a backslash. In this one
case, the usual Tcl substitutions will occur despite the
braces.
If a pattern is the keyword eof, the corresponding body is
executed upon end-of-file. If a pattern is the keyword
timeout, the corresponding body is executed upon timeout. If
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no timeout keyword is used, an implicit null action is executed
upon timeout. The default timeout period is 10 seconds but may
be set, for example to 30, by the command "set timeout 30". An
infinite timeout may be designated by the value -1. If a
pattern is the keyword default, the corresponding body is
executed upon either timeout or end-of-file.
If a pattern matches, then the corresponding body is executed.
expect returns the result of the body (or the empty string if
no pattern matched). In the event that multiple patterns
match, the one appearing first is used to select a body.
Each time new output arrives, it is compared to each pattern in
the order they are listed. Thus, you may test for absence of a
match by making the last pattern something guaranteed to
appear, such as a prompt. In situations where there is no
prompt, you must use timeout (just like you would if you were
interacting manually).
Patterns are specified in three ways. By default, patterns are
specified as with Tcl's string match command. (Such patterns
are also similar to C-shell regular expressions usually
referred to as "glob" patterns). The -gl flag may may be used
to protect patterns that might otherwise match expect flags
from doing so. Any pattern beginning with a "-" should be
protected this way. (All strings starting with "-" are
reserved for future options.)
For example, the following fragment looks for a successful
login. (Note that abort is presumed to be a procedure defined
elsewhere in the script.)
expect {
busy {print busy\n ; exp_continue}
failed abort
"invalid password" abort
timeout abort
connected
}
Quotes are necessary on the fourth pattern since it contains a
space, which would otherwise separate the pattern from the
action. Patterns with the same action (such as the 3rd and
4th) require listing the actions again. This can be avoid by
using regexp-style patterns (see below). More information on
forming glob-style patterns can be found in the Tcl manual.
Regexp-style patterns follow the syntax defined by Tcl's regexp
(short for "regular expression") command. regexp patterns are
introduced with the flag -re. The previous example can be
rewritten using a regexp as:
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EXPECT(1) EXPECT(1)
expect {
busy {print busy\n ; exp_continue}
-re "failed|invalid password" abort
timeout abort
connected
}
Both types of patterns are "unanchored". This means that
patterns do not have to match the entire string, but can begin
and end the match anywhere in the string (as long as everything
else matches). Use ^ to match the beginning of a string, and $
to match the end. Note that if you do not wait for the end of
a string, your responses can easily end up in the middle of the
string as they are echoed from the spawned process. While
still producing correct results, the output can look unnatural.
Thus, use of $ is encouraged if you can exactly describe the
characters at the end of a string.
Note that in many editors, the ^ and $ match the beginning and
end of lines respectively. However, because expect is not line
oriented, these characters match the beginning and end of the
data (as opposed to lines) currently in the expect matching
buffer. (Also, see the note below on "system indigestion.")
The -ex flag causes the pattern to be matched as an "exact"
string. No interpretation of *, ^, etc is made (although the
usual Tcl conventions must still be observed). Exact patterns
are always unanchored.
The -nocase flag causes uppercase characters of the output to
compare as if they were lowercase characters. The pattern is
not affected.
While reading output, more than 2000 bytes can force earlier
bytes to be "forgotten". This may be changed with the function
match_max. (Note that excessively large values can slow down
the pattern matcher.) If patlist is full_buffer, the
corresponding body is executed if match_max bytes have been
received and no other patterns have matched. Whether or not
the full_buffer keyword is used, the forgotten characters are
written to expect_out(buffer).
If patlist is the keyword null, and nulls are allowed (via the
remove_nulls command), the corresponding body is executed if a
single ASCII 0 is matched. It is not possible to match 0 bytes
via glob or regexp patterns.
Upon matching a pattern (or eof or full_buffer), any matching
and previously unmatched output is saved in the variable
expect_out(buffer). Up to 9 regexp substring matches are saved
in the variables expect_out(1,string) through
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expect_out(9,string). If the -indices flag is used before a
pattern, the starting and ending indices (in a form suitable
for lrange) of the 10 strings are stored in the variables
expect_out(X,start) and expect_out(X,end) where X is a digit,
corresponds to the substring position in the buffer. 0 refers
to strings which matched the entired pattern and is generated
for glob patterns as well as regexp patterns. For example, if
a process has produced output of "abcdefgh\n", the result of:
expect "cd"
is as if the following statements had executed:
set expect_out(0,string) cd
set expect_out(buffer) abcd
and "efgh\n" is left in the output buffer. If a process
produced the output "abbbcabkkkka\n", the result of:
expect -indices -re "b(b*).*(k+)"
is as if the following statements had executed:
set expect_out(0,start) 1
set expect_out(0,end) 10
set expect_out(0,string) bbbcabkkkk
set expect_out(1,start) 2
set expect_out(1,end) 3
set expect_out(1,string) bb
set expect_out(2,start) 10
set expect_out(2,end) 10
set expect_out(2,string) k
set expect_out(buffer) abbbcabkkkk
and "a\n" is left in the output buffer. The pattern "*" (and
-re ".*") will flush the output buffer without reading any more
output from the process.
Normally, the matched output is discarded from Expect's
internal buffers. This may be prevented by prefixing a pattern
with the -notransfer flag. This flag is especially useful in
experimenting (and can be abbreviated to "-n" for convenience
while experimenting).
The spawn id associated with the matching output (or eof or
full_buffer) is stored in expect_out(spawn_id).
The -timeout flag causes the current expect command to use the
following value as a timeout instead of using the value of the
timeout variable.
By default, patterns are matched against output from the
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current process, however the -i flag declares the output from
the named spawn_id list be matched against any following
patterns (up to the next -i). The spawn_id list should either
be a whitespace separated list of spawn_ids or a variable
referring to such a list of spawn_ids.
For example, the following example waits for "connected" from
the current process, or "busy", "failed" or "invalid password"
from the spawn_id named by $proc2.
expect {
-i $proc2 busy{print busy\n ; exp_continue}
-re "failed|invalid password" abort
timeout abort
connected
}
The value of the global variable any_spawn_id may be used to
match patterns to any spawn_ids that are named with all other
-i flags in the current expect command. The spawn_id from a -i
flag with no associated pattern (i.e., followed immediately by
another -i) is made available to any other patterns in the same
expect command associated with any_spawn_id.
The -i flag may also name a global variable in which case the
variable is read for a list of spawn ids. The variable is
reread whenever it changes. This provides a way of changing
the I/O source while the command is in execution. Spawn ids
provided this way are called "indirect" spawn ids.
Actions such as break and continue cause control structures
(i.e., for, proc) to behave in the usual way. The command
exp_continue allows expect itself to continue executing rather
than returning as it normally would.
This is useful for avoiding explicit loops or repeated expect
statements. The following example is part of a fragment to
automate rlogin. The exp_continue avoids having to write a
second expect statement (to look for the prompt again) if the
rlogin prompts for a password.
expect {
Password: {
stty -echo
send_user "password (for $user) on $host: "
expect_user -re "(.*)\n"
send_user "\n"
send "$expect_out(1,string)\r"
stty echo
exp_continue
} incorrect {
send_user "invalid password or account\n"
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exit
} timeout {
send_user "connection to $host timed out\n"
exit
} eof {
send_user "host connection failed: $expect_out(buffer)"
exit
} -re $prompt
}
For example, the following fragment might help a user guide an
interaction that is already totally automated. In this case,
the terminal is put into raw mode. If the user presses "+", a
variable is incremented. If "p" is pressed, several returns
are sent to the process, perhaps to poke it in some way, and
"i" lets the user interact with the process, effectively
stealing away control from the script. In each case, the
exp_continue allows the current expect to continue pattern
matching after executing the current action.
stty raw -echo
expect_after {
-i $user_spawn_id
"p" {send "\r\r\r"; exp_continue}
"+" {incr foo; exp_continue}
"i" {interact; exp_continue}
"quit" exit
}
By default, exp_continue resets the timeout timer. The timer
is not restarted, if exp_continue is called with the
-continue_timer flag.
expect_after [expect args]
works identically to the expect_before except that if patterns
from both expect and expect_after can match, the expect pattern
is used. See the expect_before command for more information.
expect_background [expect args]
takes the same arguments as expect, however it returns
immediately. Patterns are tested whenever new input arrives.
Note: this only works in the Tk environment. The pattern
timeout and default are meaningless to expect_background and
are silently discarded. Otherwise, the expect_background
command uses expect_before and expect_after patterns just like
expect does.
When expect_background actions are being evaluated, background
processing for the same spawn id is blocked. Background
processing is unblocked when the action completes. While
background processing is blocked, it is possible to do a
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(foreground) expect on the same spawn id.
It is not possible to execute an expect while an
expect_background is unblocked. expect_background for a
particular spawn id is deleted by declaring a new
expect_background with the same spawn id. Declaring
expect_background with no pattern removes the given spawn id
from the ability to match patterns in the background.
expect_before [expect args]
takes the same arguments as expect, however it returns
immediately. Pattern-action pairs from the most recent
expect_before with the same spawn id are implicitly added to
any following expect commands. If a pattern matches, it is
treated as if it had been specified in the expect command
itself, and the associated body is executed in the context of
the expect command. If patterns from both expect_before and
expect can match, the expect_before pattern is used.
If not 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).
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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).
exp_version [[-exit] version]
is useful for assuring that the script is compatible with the
current version of Expect.
With no arguments, the current version of Expect is returned.
This version may then be encoded in your script. If you
actually know that you are not using features of recent
versions, you can specify an earlier version.
Versions consist of three numbers separated by dots. First is
the major number. Scripts written for versions of Expect with
a different major number will almost certainly not work.
exp_version returns an error if the major numbers do not match.
Second is the minor number. Scripts written for a version with
a greater minor number than the current version may depend upon
some new feature and might not run. exp_version returns an
error if the major numbers match, but the script minor number
is greater than that of the running Expect.
Third is a number that plays no part in the version comparison.
However, it is incremented when the Expect software
distribution is changed in any way, such as by additional
documentation or optimization. It is reset to 0 upon each new
minor version.
With the -exit flag, Expect prints an error and exits if the
version is out of date.
fork creates a new process. The new process is an exact copy of the
current Expect process. On success, fork returns 0 to the new
(child) process and returns the process ID of the child process
to the parent process. On failure (invariably due to lack of
resources, e.g., swap space, memory), fork returns -1 to the
parent process, and no child process is created.
Forked processes exit via the exit command, just like the
original process. Forked processes are allowed to write to the
log files. If you do not disable debugging or logging in most
of the processes, the result can be confusing.
Some pty implementations may be confused by multiple readers
and writers, even momentarily. Thus, it is safest to fork
before spawning processes.
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interact [string1 body1] ... [stringn [bodyn]]
gives control of the current process to the user, so that
keystrokes are sent to the current process, and the stdout and
stderr of the current process are returned.
String-body pairs may be specified as arguments, in which case
the body is executed when the corresponding string is entered.
(By default, the string is not sent to the current process.)
The interpreter command is assumed, if the final body is
missing.
If the arguments to the entire interact statement require more
than one line, all the arguments may be "braced" into one so as
to avoid terminating each line with a backslash. In this one
case, the usual Tcl substitutions will occur despite the
braces.
For example, the following command runs interact with the
following string-body pairs defined: When ^Z is pressed,
Expect is suspended. (The -reset flag restores the terminal
modes.) When ^A is pressed, the user sees "you typed a
control-A" and the process is sent a ^A. When $ is pressed,
the user sees the date. When ^C is pressed, Expect exits. If
"foo" is entered, the user sees "bar". When ~~ is pressed, the
Expect interpreter runs interactively.
set CTRLZ \032
interact {
-reset $CTRLZ {exec kill -STOP [pid]}
\001 {send_user "you typed a control-A\n";
send "\001"
}
$ {send_user "The date is [exec date]."}
\003 exit
foo {send_user "bar"}
~~
}
In string-body pairs, strings are matched in the order they are
listed as arguments. Strings that partially match are not sent
to the current process in anticipation of the remainder coming.
If characters are then entered such that there can no longer
possibly be a match, only the part of the string will be sent
to the process that cannot possibly begin another match. Thus,
strings that are substrings of partial matches can match later,
if the original strings that was attempting to be match
ultimately fails.
By default, string matching is exact with no wild cards. (In
contrast, the expect command uses glob-style patterns by
default.) The -ex flag may be used to protect patterns that
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might otherwise match interact flags from doing so. Any
pattern beginning with a "-" should be protected this way.
(All strings starting with "-" are reserved for future
options.)
The -re flag forces the string to be interpreted as a regexpstyle
pattern. In this case, matching substrings are stored in
the variable interact_out similarly to the way expect stores
its output in the variable expect_out. The -indices flag is
similarly supported.
The pattern eof introduces an action that is executed upon
end-of-file. A separate eof pattern may also follow the
-output flag in which case it is matched if an eof is detected
while writing output. The default eof action is "return", so
that interact simply returns upon any EOF.
The pattern timeout introduces a timeout (in seconds) and
action that is executed after no characters have been read for
a given time. The timeout pattern applies to the most recently
specified process. There is no default timeout. The special
variable "timeout" (used by the expect command) has no affect
on this timeout.
For example, the following statement could be used to
autologout users who have not typed anything for an hour but
who still get frequent system messages:
interact -input $user_spawn_id timeout 3600 return -output $spawn_id
If the pattern is the keyword null, and nulls are allowed (via
the remove_nulls command), the corresponding body is executed
if a single ASCII 0 is matched. It is not possible to match 0
bytes via glob or regexp patterns.
Prefacing a pattern with the flag -iwrite causes the variable
interact_out(spawn_id) to be set to the spawn_id which matched
the pattern (or eof).
Actions such as break and continue cause control structures
(i.e., for, proc) to behave in the usual way. However return
causes interact to return to its caller, while inter_return
causes interact to cause a return in its caller. For example,
if "proc foo" called interact which then executed the action
inter_return, proc foo would return. (This means that if
interact calls interpreter interactively typing return will
cause the interact to continue, while inter_return will cause
the interact to return to its caller.)
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EXPECT(1) EXPECT(1)
During interact, raw mode is used so that all characters may be
passed to the current process. If the current process does not
catch job control signals, it will stop if sent a stop signal
(by default ^Z). To restart it, send a continue signal (such
as by "kill -CONT <pid>"). If you really want to send a
SIGSTOP to such a process (by ^Z), consider spawning csh first
and then running your program. On the other hand, if you want
to send a SIGSTOP to Expect itself, first 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 executed.
For speed, actions execute in raw mode by default. The -reset
flag resets the terminal to the mode it had before interact was
executed (invariably, cooked mode). Note that characters
entered when the mode is being switched may be lost (an
unfortunate feature of the terminal driver on some systems).
The only reason to use -reset is if your action depends on
running in cooked mode.
The -echo flag sends characters that match the following
pattern back to the process that generated them as each
character is read. This may be useful when the user needs to
see feedback from partially typed patterns.
If a pattern is being echoed but eventually fails to match, the
characters are sent to the spawned process. If the spawned
process then echoes them, the user will see the characters
twice. -echo is probably only appropriate in situations where
the user is unlikely to not complete the pattern. For example,
the following excerpt is from rftp, the recursive-ftp script,
where the user is prompted to enter ~g, ~p, or ~l, to get, put,
or list the current directory recursively. These are so far
away from the normal ftp commands, that the user is unlikely to
type ~ followed by anything else, except mistakenly, in which
case, they'll probably just ignore the result anyway.
interact {
-echo ~g {getcurdirectory 1}
-echo ~l {getcurdirectory 0}
-echo ~p {putcurdirectory}
}
The -nobuffer flag sends characters that match the following
pattern on to the output process as characters are read.
This is useful when you wish to let a program echo back the
pattern. For example, the following might be used to monitor
where a person is dialing (a Hayes-style modem). Each time
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EXPECT(1) EXPECT(1)
"atd" is seen the script logs the rest of the line.
proc lognumber {} { " return
putsr$log-"[execedate]:"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
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EXPECT(1) EXPECT(1)
$user_spawn_id -output". (Similarly, with patterns that do not
have -input.) If one -input is specified, it overrides
$user_spawn_id. If a second -input is specified, it overrides
$spawn_id. Additional -input flags may be specified.
The two implied input processes default to having their outputs
specified as $spawn_id and $user_spawn_id (in reverse). If a
-input flag appears with no -output flag, characters from that
process are discarded.
The -i flag introduces a replacement for the current spawn_id
when no other -input or -output flags are used.
It is possible to change the processes that are being
interacted with by using indirect spawn ids. (Indirect spawn
ids are described in the section on the expect command.)
Indirect spawn ids may be specified with the -i, -u, -input, or
-output flags.
exp_internal [-f file] value
causes further commands to send diagnostic information internal
to Expect to stderr if value is non-zero. This output is
disabled if value is 0. The diagnostic information includes
every character received, and every attempt made to match the
current output against the patterns.
If the optional file is supplied, all normal and debugging
output is written to that file (regardless of the value of
value). Any previous diagnostic output file is closed.
The -info flag causes exp_internal to return a description of
the most recent non-info arguments given.
interpreter
causes the user to be interactively prompted for Expect and Tcl
commands. The result of each command is printed.
Actions such as break and continue cause control structures
(i.e., for, proc) to behave in the usual way. However return
causes interpreter to return to its caller, while inter_return
causes interpreter to cause a return in its caller. For
example, if "proc foo" called interpreter which then executed
the action inter_return, proc foo would return. Any other
command causes interpreter to continue prompting for new
commands.
By default, the prompt contains two integers. The first
integer describes the depth of the evaluation stack (i.e., how
many times Tcl_Eval has been called). The second integer is
the Tcl history identifier. The prompt can be set by defining
a procedure called "prompt1" whose return value becomes the
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EXPECT(1) EXPECT(1)
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 info.)
The -a flag forces output to be logged that was suppressed by
the log_user command.
By default, the log_file command appends to old files rather
than truncating them, for the convenience of being able to turn
logging off and on multiple times in one session. To truncate
files, use the -noappend flag.
The -info flag causes log_file to return a description of the
most recent non-info arguments given.
log_user 0|1
By default, the send/expect dialogue is logged to stdout (and a
logfile if open). The logging to stdout is disabled by the
command "log_user 0" and reenabled by "log_user 1". Logging to
the logfile is unchanged.
The -info flag causes log_user to return a description of the
most recent non-info arguments given.
match_max [-d] [-i spawn_id] [size]
defines the size of the buffer (in bytes) used internally by
expect. With no size argument, the current size is returned.
With the -d flag, the default size is set. (The initial
default is 2000.) With the -i flag, the size is set for the
named spawn id, otherwise it is set for the current process.
overlay [-# spawn_id] [-# spawn_id] [...] program [args]
executes program args in place of the current Expect program,
which terminates. A bare hyphen argument forces a hyphen in
front of the command name as if it was a login shell. All
spawn_ids are closed except for those named as arguments.
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EXPECT(1) EXPECT(1)
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.
exp_pid [-i spawn_id]
returns the process id corresponding to the current spawn id or
the named spawn id.
remove_nulls [-d] [-i spawn_id] [value]
defines whether nulls are retained or removed from the output
of spawned processes before pattern matching or storing in the
variable expect_out or interact_out. If value is 1, nulls are
removed. If value is 0, nulls are not removed. With no value
argument, the current value is returned.
With the -d flag, the default value is set. (The initial
default is 1, i.e., nulls are removed.) With the -i flag, the
value is set for the named spawn id, otherwise it is set for
the current process.
Whether or not nulls are removed, Expect will record null bytes
to the log and stdout.
send [-flags] string
Sends string to the current process. For example, the command
send "hello world\r"
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EXPECT(1) EXPECT(1)
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 linebuffered
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 -0 to indicate how
many nulls to send.
The -break flag generates a break condition. This only makes
sense if the spawn id refers to a tty device opened via "spawn
-open". If you have spawned a process such as tip, you should
use tip's convention for generating a break.
The -s flag forces output to be sent "slowly", thus avoid the
common situation where a computer outtypes an input buffer that
was designed for a human who would never outtype the same
buffer. This output is controlled by the value of the variable
"send_slow" which takes a two element list. The first element
is an integer that describes the number of bytes to send
atomically. The second element is a real number that describes
the number of seconds by which the atomic sends must be
separated. For example, "set send_slow {10 .001}" would force
"send -s" to send strings with 1 millisecond in between each 10
characters sent.
The -h flag forces output to be sent (somewhat) like a human
actually typing. Human-like delays appear between the
characters. (The algorithm is based upon a Weibull
distribution, with modifications to suit this particular
application.) This output is controlled by the value of the
variable "send_human" which takes a five element list. The
first two elements are average interarrival time of characters
in seconds. The first is used by default. The second is used
at word endings, to simulate the subtle pauses that
occasionally occur at such transitions. The third parameter is
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EXPECT(1) EXPECT(1)
a measure of varibility where .1 is quite variable, 1 is
reasonably variable, and 10 is quite invariable. The extremes
are 0 to infinity. The last two parameters are, respectively,
a minimum and maximum interarrival time. The minimum and
maximum are used last and "clip" the final time. The ultimate
average can be quite different from the given average if the
minimum and miximum clip enough values.
As an example, the following command emulates a fast and
consistent typist:
set send_human {.1 .3 1 .05 2}
send -h "I'm hungry. Let's do lunch."
while the following might be more suitable after a hangover:
set send_human {.4 .4 .2 .5 100}
send -h "Goodd party lash night!"
Note that errors are not simulated, although you can set up
error correction situations yourself by embedding mistakes and
corrections in a send argument.
It is a good idea to precede the first send to a process by an
expect. expect will wait for the process to start, while send
cannot. In particular, if the first send completes before the
process starts running, you run the risk of having your data
ignored. In situations where interactive programs offer no
initial prompt, you can precede send by a delay as in:
# To avoid giving hackers hints on how to break in,
# this system does not prompt for an external password.
# Wait for 5 seconds for exec to complete
spawn telnet very.secure.gov
sleep 5
send password\r
exp_send is an alias for send. If you are using Expectk or
some other variant of Expect in the Tk environment, send is
defined by Tk for an entirely different purpose. exp_send is
provided for compatibility between environments. Similar
aliases are provided for other Expect's other send commands.
send_error string
is like send, except that the string 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.
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EXPECT(1) EXPECT(1)
send_tty string
is like send, except that the string is sent to /dev/tty rather
than the current process.
send_user [args] string
is like send, except that the arguments are sent to stdout
rather than the current process.
sleepseconds
causes the script to sleep for the given number of seconds.
Seconds may be a decimal number. Interrupts (and Tk events if
you are using Expectk) are processed while Expect sleeps.
spawn [args] program [args]
creates a new process running program args. Its stdin, stdout
and stderr are connected to Expect, so that they may be read
and written by other Expect commands. The connection is broken
by close or if the process itself closes any of the file
identifiers.
When a process is started by spawn, the variable spawn_id is
set to a descriptor referring to that process. The process
described by spawn_id is considered the current process.
spawn_id may be read or written, in effect providing job
control.
user_spawn_id is a global variable containing a descriptor
which refers to the user. For example, when spawn_id is set to
this value, expect behaves like expect_user.
error_spawn_id is a global variable containing a descriptor
which refers to the standard error. For example, when spawn_id
is set to this value, send behaves like send_error.
tty_spawn_id is a
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