NAME¶
Expect.pm - Expect for Perl
VERSION¶
1.21
SYNOPSIS¶
use Expect;
# create an Expect object by spawning another process
my $exp = Expect->spawn($command, @params)
or die "Cannot spawn $command: $!\n";
# or by using an already opened filehandle (e.g. from Net::Telnet)
my $exp = Expect->exp_init(\*FILEHANDLE);
# if you prefer the OO mindset:
my $exp = new Expect;
$exp->raw_pty(1);
$exp->spawn($command, @parameters)
or die "Cannot spawn $command: $!\n";
# send some string there:
$exp->send("string\n");
# or, for the filehandle mindset:
print $exp "string\n";
# then do some pattern matching with either the simple interface
$patidx = $exp->expect($timeout, @match_patterns);
# or multi-match on several spawned commands with callbacks,
# just like the Tcl version
$exp->expect($timeout,
[ qr/regex1/ => sub { my $exp = shift;
$exp->send("response\n");
exp_continue; } ],
[ "regexp2" , \&callback, @cbparms ],
);
# if no longer needed, do a soft_close to nicely shut down the command
$exp->soft_close();
# or be less patient with
$exp->hard_close();
Expect.pm is built to either spawn a process or take an existing filehandle and
interact with it such that normally interactive tasks can be done without
operator assistance. This concept makes more sense if you are already familiar
with the versatile Tcl version of Expect. The public functions that make up
Expect.pm are:
Expect->new()
Expect::interconnect(@objects_to_be_read_from)
Expect::test_handles($timeout, @objects_to_test)
Expect::version($version_requested | undef);
$object->spawn(@command)
$object->clear_accum()
$object->set_accum($value)
$object->debug($debug_level)
$object->exp_internal(0 | 1)
$object->notransfer(0 | 1)
$object->raw_pty(0 | 1)
$object->stty(@stty_modes) # See the IO::Stty docs
$object->slave()
$object->before();
$object->match();
$object->after();
$object->matchlist();
$object->match_number();
$object->error();
$object->command();
$object->exitstatus();
$object->pty_handle();
$object->do_soft_close();
$object->restart_timeout_upon_receive(0 | 1);
$object->interact($other_object, $escape_sequence)
$object->log_group(0 | 1 | undef)
$object->log_user(0 | 1 | undef)
$object->log_file("filename" | $filehandle | \&coderef | undef)
$object->manual_stty(0 | 1 | undef)
$object->match_max($max_buffersize or undef)
$object->pid();
$object->send_slow($delay, @strings_to_send)
$object->set_group(@listen_group_objects | undef)
$object->set_seq($sequence,\&function,\@parameters);
There are several configurable package variables that affect the behavior of
Expect. They are:
$Expect::Debug;
$Expect::Exp_Internal;
$Expect::IgnoreEintr;
$Expect::Log_Group;
$Expect::Log_Stdout;
$Expect::Manual_Stty;
$Expect::Multiline_Matching;
$Expect::Do_Soft_Close;
DESCRIPTION¶
The Expect module is a successor of Comm.pl and a descendent of Chat.pl. It more
closely ressembles the Tcl Expect language than its predecessors. It does not
contain any of the networking code found in Comm.pl. I suspect this would be
obsolete anyway given the advent of IO::Socket and external tools such as
netcat.
Expect.pm is an attempt to have more of a
switch() & case feeling to
make decision processing more fluid. Three separate types of debugging have
been implemented to make code production easier.
It is possible to interconnect multiple file handles (and processes) much like
Tcl's Expect. An attempt was made to enable all the features of Tcl's Expect
without forcing Tcl on the victim programmer :-) .
Please, before you consider using Expect, read the FAQs about "I want to
automate password entry for su/ssh/scp/rsh/..." and "I want to use
Expect to automate [anything with a buzzword]..."
USAGE¶
- new Expect ()
- Creates a new Expect object, i.e. a pty. You can change
parameters on it before actually spawning a command. This is important if
you want to modify the terminal settings for the slave. See slave()
below. The object returned is actually a reblessed IO::Pty filehandle, so
see there for additional methods.
- Expect->exp_init(\*FILEHANDLE) or
- Expect->init(\*FILEHANDLE)
- Initializes $new_handle_object for use with other Expect
functions. It must be passed a _reference_ to FILEHANDLE if you
want it to work properly. IO::File objects are preferable. Returns a
reference to the newly created object.
You can use only real filehandles, certain tied filehandles (e.g. Net::SSH2)
that lack a fileno() will not work. Net::Telnet objects can be used
but have been reported to work only for certain hosts. YMMV.
- Expect->spawn($command, @parameters) or
- $object->spawn($command, @parameters) or
- new Expect ($command, @parameters)
- Forks and execs $command. Returns an Expect object upon
success or "undef" if the fork was unsuccessful or the command
could not be found. spawn() passes its parameters unchanged to
Perls exec(), so look there for detailed semantics.
Note that if spawn cannot exec() the given command, the Expect object
is still valid and the next expect() will see "Cannot
exec", so you can use that for error handling.
Also note that you cannot reuse an object with an already spawned command,
even if that command has exited. Sorry, but you have to allocate a new
object...
- $object->debug(0 | 1 | 2 | 3 | undef)
- Sets debug level for $object. 1 refers to general debugging
information, 2 refers to verbose debugging and 0 refers to no debugging.
If you call debug() with no parameters it will return the current
debugging level. When the object is created the debugging level will match
that $Expect::Debug, normally 0.
The '3' setting is new with 1.05, and adds the additional functionality of
having the _full_ accumulated buffer printed every time data is read from
an Expect object. This was implemented by request. I recommend against
using this unless you think you need it as it can create quite a quantity
of output under some circumstances..
- $object->exp_internal(1 | 0)
- Sets/unsets 'exp_internal' debugging. This is similar in
nature to its Tcl counterpart. It is extremely valuable when debugging
expect() sequences. When the object is created the exp_internal
setting will match the value of $Expect::Exp_Internal, normally 0. Returns
the current setting if called without parameters. It is highly recommended
that you make use of the debugging features lest you have angry code.
- $object->raw_pty(1 | 0)
- Set pty to raw mode before spawning. This disables echoing,
CR->LF translation and an ugly hack for broken Solaris TTYs (which send
<space><backspace> to slow things down) and thus gives a more
pipe-like behaviour (which is important if you want to transfer binary
content). Note that this must be set before spawning the
program.
- $object->stty(qw(mode1 mode2...))
- Sets the tty mode for $object's associated terminal to the
given modes. Note that on many systems the master side of the pty is not a
tty, so you have to modify the slave pty instead, see next item. This
needs IO::Stty installed, which is no longer required.
- $object->slave()
- Returns a filehandle to the slave part of the pty. Very
useful in modifying the terminal settings:
$object->slave->stty(qw(raw -echo));
Typical values are 'sane', 'raw', and 'raw -echo'. Note that I recommend
setting the terminal to 'raw' or 'raw -echo', as this avoids a lot of
hassle and gives pipe-like (i.e. transparent) behaviour (without the
buffering issue).
- $object->print(@strings) or
- $object->send(@strings)
- Sends the given strings to the spawned command. Note that
the strings are not logged in the logfile (see print_log_file) but will
probably be echoed back by the pty, depending on pty settings (default is
echo) and thus end up there anyway. This must also be taken into account
when expect()ing for an answer: the next string will be the command
just sent. I suggest setting the pty to raw, which disables echo and makes
the pty transparently act like a bidirectional pipe.
- $object->expect($timeout, @match_patterns)
- or, more like Tcl/Expect,
expect($timeout,
'-i', [ $obj1, $obj2, ... ],
[ $re_pattern, sub { ...; exp_continue; }, @subparms, ],
[ 'eof', sub { ... } ],
[ 'timeout', sub { ... }, \$subparm1 ],
'-i', [ $objn, ...],
'-ex', $exact_pattern, sub { ... },
$exact_pattern, sub { ...; exp_continue_timeout; },
'-re', $re_pattern, sub { ... },
'-i', \@object_list, @pattern_list,
...);
Simple interface:
Given $timeout in seconds Expect will wait for $object's handle to produce
one of the match_patterns, which are matched exactly by default. If you
want a regexp match, prefix the pattern with '-re'.
Due to o/s limitations $timeout should be a round number. If $timeout is 0
Expect will check one time to see if $object's handle contains any of the
match_patterns. If $timeout is undef Expect will wait forever for a
pattern to match.
If called in a scalar context, expect() will return the position of
the matched pattern within $match_patterns, or undef if no pattern was
matched. This is a position starting from 1, so if you want to know which
of an array of @matched_patterns matched you should subtract one from the
return value.
If called in an array context expect() will return
($matched_pattern_position, $error, $successfully_matching_string,
$before_match, and $after_match).
$matched_pattern_position will contain the value that would have been
returned if expect() had been called in a scalar context. $error is
the error that occurred that caused expect() to return. $error will
contain a number followed by a string equivalent expressing the nature of
the error. Possible values are undef, indicating no error, '1:TIMEOUT'
indicating that $timeout seconds had elapsed without a match, '2:EOF'
indicating an eof was read from $object, '3: spawn id($fileno) died'
indicating that the process exited before matching and '4:$!' indicating
whatever error was set in $ERRNO during the last read on $object's handle
or during select(). All handles indicated by set_group plus STDOUT
will have all data to come out of $object printed to them during
expect() if log_group and log_stdout are set.
Changed from older versions is the regular expression handling. By default
now all strings passed to expect() are treated as literals. To
match a regular expression pass '-re' as a parameter in front of the
pattern you want to match as a regexp.
Example:
$object->expect(15, 'match me exactly','-re','match\s+me\s+exactly');
This change makes it possible to match literals and regular expressions in
the same expect() call.
Also new is multiline matching. ^ will now match the beginning of lines.
Unfortunately, because perl doesn't use $/ in determining where lines
break using $ to find the end of a line frequently doesn't work. This is
because your terminal is returning "\r\n" at the end of every
line. One way to check for a pattern at the end of a line would be to use
\r?$ instead of $.
Example: Spawning telnet to a host, you might look for the escape character.
telnet would return to you "\r\nEscape character is '^]'.\r\n".
To find this you might use $match='^Escape char.*\.\r?$';
$telnet->expect(10,'-re',$match);
New more Tcl/Expect-like interface:
It's now possible to expect on more than one connection at a time by
specifying '"-i"' and a single Expect object or a ref to an
array containing Expect objects, e.g.
expect($timeout,
'-i', $exp1, @patterns_1,
'-i', [ $exp2, $exp3 ], @patterns_2_3,
)
Furthermore, patterns can now be specified as array refs containing
[$regexp, sub { ...}, @optional_subprams] . When the pattern matches, the
subroutine is called with parameters ($matched_expect_obj,
@optional_subparms). The subroutine can return the symbol `exp_continue'
to continue the expect matching with timeout starting anew or return the
symbol `exp_continue_timeout' for continuing expect without resetting the
timeout count.
$exp->expect($timeout,
[ qr/username: /i, sub { my $self = shift;
$self->send("$username\n");
exp_continue; }],
[ qr/password: /i, sub { my $self = shift;
$self->send("$password\n");
exp_continue; }],
$shell_prompt);
`expect' is now exported by default.
- $object->exp_before() or
- $object->before()
- before() returns the 'before' part of the last
expect() call. If the last expect() call didn't match
anything, exp_before() will return the entire output of the object
accumulated before the expect() call finished.
Note that this is something different than Tcl Expects
before()!!
- $object->exp_after() or
- $object->after()
- returns the 'after' part of the last expect() call.
If the last expect() call didn't match anything, exp_after()
will return undef().
- $object->exp_match() or
- $object->match()
- returns the string matched by the last expect()
call, undef if no string was matched.
- $object->exp_match_number() or
- $object->match_number()
- exp_match_number() returns the number of the pattern
matched by the last expect() call. Keep in mind that the first
pattern in a list of patterns is 1, not 0. Returns undef if no pattern was
matched.
- $object->exp_matchlist() or
- $object->matchlist()
- exp_matchlist() returns a list of matched substrings
from the brackets () inside the regexp that last matched.
($object->matchlist)[0] thus corresponds to $1,
($object->matchlist)[1] to $2, etc.
- $object->exp_error() or
- $object->error()
- exp_error() returns the error generated by the last
expect() call if no pattern was matched. It is typically useful to
examine the value returned by before() to find out what the output
of the object was in determining why it didn't match any of the
patterns.
- $object->clear_accum()
- Clear the contents of the accumulator for $object. This
gets rid of any residual contents of a handle after expect() or
send_slow() such that the next expect() call will only see
new data from $object. The contents of the accumulator are returned.
- $object->set_accum($value)
- Sets the content of the accumulator for $object to $value.
The previous content of the accumulator is returned.
- $object->exp_command() or
- $object->command()
- exp_command() returns the string that was used to
spawn the command. Helpful for debugging and for reused patternmatch
subroutines.
- $object->exp_exitstatus() or
- $object->exitstatus()
- Returns the exit status of $object (if it already
exited).
- $object->exp_pty_handle() or
- $object->pty_handle()
- Returns a string representation of the attached pty, for
example: `spawn id(5)' (pty has fileno 5), `handle id(7)'
(pty was initialized from fileno 7) or `STDIN'. Useful for debugging.
- $object->restart_timeout_upon_receive(0 | 1)
- If this is set to 1, the expect timeout is retriggered
whenever something is received from the spawned command. This allows to
perform some aliveness testing and still expect for patterns.
$exp->restart_timeout_upon_receive(1);
$exp->expect($timeout,
[ timeout => \&report_timeout ],
[ qr/pattern/ => \&handle_pattern],
);
Now the timeout isn't triggered if the command produces any kind of output,
i.e. is still alive, but you can act upon patterns in the output.
- $object->notransfer(1 | 0)
- Do not truncate the content of the accumulator after a
match. Normally, the accumulator is set to the remains that come after the
matched string. Note that this setting is per object and not per pattern,
so if you want to have normal acting patterns that truncate the
accumulator, you have to add a
$exp->set_accum($exp->after);
to their callback, e.g.
$exp->notransfer(1);
$exp->expect($timeout,
# accumulator not truncated, pattern1 will match again
[ "pattern1" => sub { my $self = shift;
...
} ],
# accumulator truncated, pattern2 will not match again
[ "pattern2" => sub { my $self = shift;
...
$self->set_accum($self->after());
} ],
);
This is only a temporary fix until I can rewrite the pattern matching part
so it can take that additional -notransfer argument.
- Expect::interconnect(@objects);
- Read from @objects and print to their @listen_groups until
an escape sequence is matched from one of @objects and the associated
function returns 0 or undef. The special escape sequence 'EOF' is matched
when an object's handle returns an end of file. Note that it is not
necessary to include objects that only accept data in @objects since the
escape sequence is _read_ from an object. Further note that the
listen_group for a write-only object is always empty. Why would you want
to have objects listening to STDOUT (for example)? By default every member
of @objects _as well as every member of its listen group_ will be set to
'raw -echo' for the duration of interconnection. Setting $object->
manual_stty() will stop this behavior per object. The original tty
settings will be restored as interconnect exits.
For a generic way to interconnect processes, take a look at IPC::Run.
- Expect::test_handles($timeout, @objects)
- Given a set of objects determines which objects' handles
have data ready to be read. Returns an array who's members are
positions in @objects that have ready handles. Returns undef if there are
no such handles ready.
- Expect::version($version_requested or undef);
- Returns current version of Expect. As of .99 earlier
versions are not supported. Too many things were changed to make
versioning possible.
- $object->interact( "\*FILEHANDLE,
$escape_sequence")
- interact() is essentially a macro for calling
interconnect() for connecting 2 processes together. \*FILEHANDLE
defaults to \*STDIN and $escape_sequence defaults to undef. Interaction
ceases when $escape_sequence is read from FILEHANDLE, not $object.
$object's listen group will consist solely of \*FILEHANDLE for the
duration of the interaction. \*FILEHANDLE will not be echoed on
STDOUT.
- $object->log_group(0 | 1 | undef)
- Set/unset logging of $object to its 'listen group'. If set
all objects in the listen group will have output from $object printed to
them during $object-> expect(), $object->send_slow(),
and "Expect::interconnect($object , ...)". Default value is on.
During creation of $object the setting will match the value of
$Expect::Log_Group, normally 1.
- $object->log_user(0 | 1 | undef) or
- $object->log_stdout(0 | 1 | undef)
- Set/unset logging of object's handle to STDOUT. This
corresponds to Tcl's log_user variable. Returns current setting if called
without parameters. Default setting is off for initialized handles. When a
process object is created (not a filehandle initialized with exp_init) the
log_stdout setting will match the value of $Expect::Log_Stdout variable,
normally 1. If/when you initialize STDIN it is usually associated with a
tty which will by default echo to STDOUT anyway, so be careful or you will
have multiple echoes.
- $object->log_file("filename" | $filehandle |
\&coderef | undef)
- Log session to a file. All characters send to or received
from the spawned process are written to the file. Normally appends to the
logfile, but you can pass an additional mode of "w" to truncate
the file upon open():
$object->log_file("filename", "w");
Returns the logfilehandle.
If called with an undef value, stops logging and closes logfile:
$object->log_file(undef);
If called without argument, returns the logfilehandle:
$fh = $object->log_file();
Can be set to a code ref, which will be called instead of printing to the
logfile:
$object->log_file(\&myloggerfunc);
- $object->print_log_file(@strings)
- Prints to logfile (if opened) or calls the logfile hook
function. This allows the user to add arbitraty text to the logfile. Note
that this could also be done as $object->log_file-> print()
but would only work for log files, not code hooks.
- $object->set_seq($sequence, \&function,
\@function_parameters)
- During Expect->interconnect() if $sequence is
read from $object &function will be executed with parameters
@function_parameters. It is _highly recommended_ that the
escape sequence be a single character since the likelihood is great that
the sequence will be broken into to separate reads from the $object's
handle, making it impossible to strip $sequence from getting printed to
$object's listen group. \&function should be something like
'main::control_w_function' and @function_parameters should be an array
defined by the caller, passed by reference to set_seq(). Your
function should return a non-zero value if execution of
interconnect() is to resume after the function returns, zero or
undefined if interconnect() should return after your function
returns. The special sequence 'EOF' matches the end of file being reached
by $object. See interconnect() for details.
- $object->set_group(@listener_objects)
- @listener_objects is the list of objects that should have
their handles printed to by $object when Expect::interconnect,
$object-> expect() or $object-> send_slow() are
called. Calling w/out parameters will return the current list of the
listener objects.
- $object->manual_stty(0 | 1 | undef)
- Sets/unsets whether or not Expect should make reasonable
guesses as to when and how to set tty parameters for $object. Will match
$Expect::Manual_Stty value (normally 0) when $object is created. If called
without parameters manual_stty() will return the current
manual_stty setting.
- $object->match_max($maximum_buffer_length | undef)
or
- $object->max_accum($maximum_buffer_length | undef)
- Set the maximum accumulator size for object. This is useful
if you think that the accumulator will grow out of hand during
expect() calls. Since the buffer will be matched by every
match_pattern it may get slow if the buffer gets too large. Returns
current value if called without parameters. Not defined by default.
- $object->notransfer(0 | 1)
- If set, matched strings will not be deleted from the
accumulator. Returns current value if called without parameters. False by
default.
- $object->exp_pid() or
- $object->pid()
- Return pid of $object, if one exists. Initialized
filehandles will not have pids (of course).
- $object->send_slow($delay, @strings);
- print each character from each string of @strings one at a
time with $delay seconds before each character. This is handy for devices
such as modems that can be annoying if you send them data too fast. After
each character $object will be checked to determine whether or not it has
any new data ready and if so update the accumulator for future
expect() calls and print the output to STDOUT and @listen_group if
log_stdout and log_group are appropriately set.
Configurable Package Variables:¶
- $Expect::Debug
- Defaults to 0. Newly created objects have a
$object->debug() value of $Expect::Debug. See $object->
debug();
- $Expect::Do_Soft_Close
- Defaults to 0. When destroying objects, soft_close may take
up to half a minute to shut everything down. From now on, only hard_close
will be called, which is less polite but still gives the process a chance
to terminate properly. Set this to '1' for old behaviour.
- $Expect::Exp_Internal
- Defaults to 0. Newly created objects have a
$object->exp_internal() value of $Expect::Exp_Internal. See
$object-> exp_internal().
- $Expect::IgnoreEintr
- Defaults to 0. If set to 1, when waiting for new data,
Expect will ignore EINTR errors and restart the select() call
instead.
- $Expect::Log_Group
- Defaults to 1. Newly created objects have a
$object->log_group() value of $Expect::Log_Group. See
$object-> log_group().
- $Expect::Log_Stdout
- Defaults to 1 for spawned commands, 0 for file handles
attached with exp_init(). Newly created objects have a $object->
log_stdout() value of $Expect::Log_Stdout. See $object->
log_stdout().
- $Expect::Manual_Stty
- Defaults to 0. Newly created objects have a
$object->manual_stty() value of $Expect::Manual_Stty. See
$object-> manual_stty().
- $Expect::Multiline_Matching
-
Defaults to 1. Affects whether or not expect() uses the /m flag for
doing regular expression matching. If set to 1 /m is used.
This makes a difference when you are trying to match ^ and $. If
you have this on you can match lines in the middle of a page of output
using ^ and $ instead of it matching the beginning and end of the entire
expression. I think this is handy.
CONTRIBUTIONS¶
Lee Eakin <leakin@japh.itg.ti.com> has ported the kibitz script from
Tcl/Expect to Perl/Expect.
Jeff Carr <jcarr@linuxmachines.com> provided a simple example of how
handle terminal window resize events (transmitted via the WINCH signal) in a
ssh session.
You can find both scripts in the examples/ subdir. Thanks to both!
Historical notes:
There are still a few lines of code dating back to the inspirational Comm.pl and
Chat.pl modules without which this would not have been possible. Kudos to Eric
Arnold <Eric.Arnold@Sun.com> and Randal 'Nuke your NT box with one line
of perl code' Schwartz<merlyn@stonehenge.com> for making these available
to the perl public.
As of .98 I think all the old code is toast. No way could this have been done
without it though. Special thanks to Graham Barr for helping make sense of the
IO::Handle stuff as well as providing the highly recommended IO::Tty module.
REFERENCES¶
Mark Rogaski <rogaski@att.com> wrote:
"I figured that you'd like to know that Expect.pm has been very useful to
AT&T Labs over the past couple of years (since I first talked to Austin
about design decisions). We use Expect.pm for managing the switches in our
network via the telnet interface, and such automation has significantly
increased our reliability. So, you can honestly say that one of the largest
digital networks in existence (AT&T Frame Relay) uses Expect.pm quite
extensively."
FAQ - Frequently Asked Questions¶
This is a growing collection of things that might help. Please send you
questions that are not answered here to RGiersig@cpan.org
What systems does Expect run on?¶
Expect itself doesn't have real system dependencies, but the underlying IO::Tty
needs pseudoterminals. IO::Stty uses POSIX.pm and Fcntl.pm.
I have used it on Solaris, Linux and AIX, others report *BSD and OSF as working.
Generally, any modern POSIX Unix should do, but there are exceptions to every
rule. Feedback is appreciated.
See IO::Tty for a list of verified systems.
Can I use this module with ActivePerl on Windows?¶
Up to now, the answer was 'No', but this has changed.
You still cannot use ActivePerl, but if you use the Cygwin environment
(
http://sources.redhat.com), which brings its own perl, and have the latest
IO::Tty (v0.05 or later) installed, it should work (feedback appreciated).
The examples in the tutorial don't work!¶
The tutorial is hopelessly out of date and needs a serious overhaul. I
appologize for this, I have concentrated my efforts mainly on the
functionality. Volunteers welcomed.
How can I find out what Expect is doing?¶
If you set
$Expect::Exp_Internal = 1;
Expect will tell you very verbosely what it is receiving and sending, what
matching it is trying and what it found. You can do this on a per-command base
with
$exp->exp_internal(1);
You can also set
$Expect::Debug = 1; # or 2, 3 for more verbose output
or
$exp->debug(1);
which gives you even more output.
I am seeing the output of the command I spawned. Can I turn that
off?¶
Yes, just set
$Expect::Log_Stdout = 0;
to globally disable it or
$exp->log_stdout(0);
for just that command. 'log_user' is provided as an alias so Tcl/Expect user get
a DWIM experience... :-)
No, I mean that when I send some text to the spawned process, it
gets echoed back and I have to deal with it in the next expect.¶
This is caused by the pty, which has probably 'echo' enabled. A solution would
be to set the pty to raw mode, which in general is cleaner for communication
between two programs (no more unexpected character translations).
Unfortunately this would break a lot of old code that sends "\r" to
the program instead of "\n" (translating this is also handled by the
pty), so I won't add this to Expect just like that. But feel free to
experiment with "$exp->raw_pty(1)".
How do I send control characters to a process?¶
A: You can send any characters to a process with the print command. To represent
a control character in Perl, use \c followed by the letter. For example,
control-G can be represented with "\cG" . Note that this will not
work if you single-quote your string. So, to send control-C to a process in
$exp, do:
print $exp "\cC";
Or, if you prefer:
$exp->send("\cC");
The ability to include control characters in a string like this is provided by
Perl, not by Expect.pm . Trying to learn Expect.pm without a thorough
grounding in Perl can be very daunting. We suggest you look into some of the
excellent Perl learning material, such as the books _Programming Perl_ and
_Learning Perl_ by O'Reilly, as well as the extensive online Perl
documentation available through the perldoc command.
My script fails from time to time without any obvious reason. It
seems that I am sometimes loosing output from the spawned program.¶
You could be exiting too fast without giving the spawned program enough time to
finish. Try adding $exp->
soft_close() to terminate the program
gracefully or do an
expect() for 'eof'.
Alternatively, try adding a 'sleep 1' after you
spawn() the program. It
could be that pty creation on your system is just slow (but this is rather
improbable if you are using the latest IO-Tty).
I want to automate password entry for su/ssh/scp/rsh/...¶
You shouldn't use Expect for this. Putting passwords, especially root passwords,
into scripts in clear text can mean severe security problems. I strongly
recommend using other means. For 'su', consider switching to 'sudo', which
gives you root access on a per-command and per-user basis without the need to
enter passwords. 'ssh'/'scp' can be set up with RSA authentication without
passwords. 'rsh' can use the .rhost mechanism, but I'd strongly suggest to
switch to 'ssh'; to mention 'rsh' and 'security' in the same sentence makes an
oxymoron.
It will work for 'telnet', though, and there are valid uses for it, but you
still might want to consider using 'ssh', as keeping cleartext passwords
around is very insecure.
I want to use Expect to automate [anything with a
buzzword]...¶
Are you sure there is no other, easier way? As a rule of thumb, Expect is useful
for automating things that expect to talk to a human, where no formal standard
applies. For other tasks that do follow a well-defined protocol, there are
often better-suited modules that already can handle those protocols. Don't try
to do HTTP requests by spawning telnet to port 80, use LWP instead. To
automate FTP, take a look at Net::FTP or "ncftp"
(
http://www.ncftp.org). You don't use a screwdriver to hammer in your nails
either, or do you?
Is it possible to use threads with Expect?¶
Basically yes, with one restriction: you must
spawn() your programs in
the main thread and then pass the Expect objects to the handling threads. The
reason is that
spawn() uses
fork(), and perlthrtut:
"Thinking of mixing fork() and threads? Please lie down and wait until the feeling passes."
I want to log the whole session to a file.¶
Use
$exp->log_file("filename");
or
$exp->log_file($filehandle);
or even
$exp->log_file(\&log_procedure);
for maximum flexibility.
Note that the logfile is appended to by default, but you can specify an optional
mode "w" to truncate the logfile:
$exp->log_file("filename", "w");
To stop logging, just call it with a false argument:
$exp->log_file(undef);
How can I turn off multi-line matching for my regexps?¶
To globally unset multi-line matching for all regexps:
$Expect::Multiline_Matching = 0;
You can do that on a per-regexp basis by stating "(?-m)" inside the
regexp (you need perl5.00503 or later for that).
How can I expect on multiple spawned commands?¶
You can use the
-i parameter to specify a single object or a list of
Expect objects. All following patterns will be evaluated against that list.
You can specify
-i multiple times to create groups of objects and
patterns to match against within the same expect statement.
This works just like in Tcl/Expect.
See the source example below.
I seem to have problems with ptys!¶
Well, pty handling is really a black magic, as it is extremely system dependend.
I have extensively revised IO-Tty, so these problems should be gone.
If your system is listed in the "verified" list of IO::Tty, you
probably have some non-standard setup, e.g. you compiled your Linux-kernel
yourself and disabled ptys. Please ask your friendly sysadmin for help.
If your system is not listed, unpack the latest version of IO::Tty, do a 'perl
Makefile.PL; make; make test; uname "-a"' and send me the results
and I'll see what I can deduce from that.
I just want to read the output of a process without
expect()ing anything. How can I do this?¶
[ Are you sure you need Expect for this? How about
qx() or
open("prog|")? ]
By using expect without any patterns to match.
$process->expect(undef); # Forever until EOF
$process->expect($timeout); # For a few seconds
$process->expect(0); # Is there anything ready on the handle now?
Ok, so now how do I get what was read on the handle?¶
$read = $process->before();
Where's IO::Pty?¶
Find it on CPAN as IO-Tty, which provides both.
How come when I automate the passwd program to change passwords
for me passwd dies before changing the password sometimes/every time?¶
What's happening is you are closing the handle before passwd exits. When you
close the handle to a process, it is sent a signal (SIGPIPE?) telling it that
STDOUT has gone away. The default behavior for processes is to die in this
circumstance. Two ways you can make this not happen are:
$process->soft_close();
This will wait 15 seconds for a process to come up with an EOF by itself before
killing it.
$process->expect(undef);
This will wait forever for the process to match an empty set of patterns. It
will return when the process hits an EOF.
As a rule, you should always
expect() the result of your transaction
before you continue with processing.
How come when I try to make a logfile with log_file() or
set_group() it doesn't print anything after the last time I run
expect()?¶
Output is only printed to the logfile/group when Expect reads from the process,
during
expect(),
send_slow() and
interconnect(). One way
you can force this is to make use of
$process->expect(undef);
and
$process->expect(0);
which will make
expect() run with an empty pattern set forever or just
for an instant to capture the output of $process. The output is available in
the accumulator, so you can grab it using $process->
before().
I seem to have problems with terminal settings, double echoing,
etc.¶
Tty settings are a major pain to keep track of. If you find unexpected behavior
such as double-echoing or a frozen session, doublecheck the documentation for
default settings. When in doubt, handle them yourself using $exp->
stty() and
manual_stty() functions. As of .98 you shouldn't have
to worry about stty settings getting fouled unless you use interconnect or
intentionally change them (like doing -echo to get a password).
If you foul up your terminal's tty settings, kill any hung processes and enter
'stty sane' at a shell prompt. This should make your terminal manageable
again.
Note that IO::Tty returns ptys with your systems default setting regarding
echoing, CRLF translation etc. and Expect does not change them. I have
considered setting the ptys to 'raw' without any translation whatsoever, but
this would break a lot of existing things, as '\r' translation would not work
anymore. On the other hand, a raw pty works much like a pipe and is more
WYGIWYE (what you get is what you expect), so I suggest you set it to 'raw' by
yourself:
$exp = new Expect;
$exp->raw_pty(1);
$exp->spawn(...);
To disable echo:
$exp->slave->stty(qw(-echo));
I'm spawning a telnet/ssh session and then let the user interact
with it. But screen-oriented applications on the other side don't work
properly.¶
You have to set the terminal screen size for that. Luckily, IO::Pty already has
a method for that, so modify your code to look like this:
my $exp = new Expect;
$exp->slave->clone_winsize_from(\*STDIN);
$exp->spawn("telnet somehost);
Also, some applications need the TERM shell variable set so they know how to
move the cursor across the screen. When logging in, the remote shell sends a
query (Ctrl-Z I think) and expects the terminal to answer with a string, e.g.
'xterm'. If you really want to go that way (be aware, madness lies at its
end), you can handle that and send back the value in $ENV{TERM}. This is only
a hand-waving explanation, please figure out the details by yourself.
I set the terminal size as explained above, but if I resize the
window, the application does not notice this.¶
You have to catch the signal WINCH ("window size changed"), change the
terminal size and propagate the signal to the spawned application:
my $exp = new Expect;
$exp->slave->clone_winsize_from(\*STDIN);
$exp->spawn("ssh somehost);
$SIG{WINCH} = \&winch;
sub winch {
$exp->slave->clone_winsize_from(\*STDIN);
kill WINCH => $exp->pid if $exp->pid;
$SIG{WINCH} = \&winch;
}
$exp->interact();
There is an example file ssh.pl in the examples/ subdir that shows how this
works with ssh. Please note that I do strongly object against using Expect to
automate ssh login, as there are better way to do that (see ssh-keygen).
I noticed that the test uses a string that resembles, but not
exactly matches, a well-known sentence that contains every character. What
does that mean?¶
That means you are anal-retentive. :-) [Gotcha there!]
I get a "Could not assign a pty" error when running as
a non-root user on an IRIX box?¶
The OS may not be configured to grant additional pty's (pseudo terminals) to
non-root users. /usr/sbin/mkpts should be 4755, not 700 for this to work. I
don't know about security implications if you do this.
How come I don't notice when the spawned process closes its
stdin/out/err??¶
You are probably on one of the systems where the master doesn't get an EOF when
the slave closes stdin/out/err.
One possible solution is when you spawn a process, follow it with a unique
string that would indicate the process is finished.
$process = Expect->spawn('telnet somehost; echo ____END____');
And then $process->expect($timeout,'____END____','other','patterns');
Source Examples¶
How to automate login¶
my $telnet = new Net::Telnet ("remotehost") # see Net::Telnet
or die "Cannot telnet to remotehost: $!\n";;
my $exp = Expect->exp_init($telnet);
# deprecated use of spawned telnet command
# my $exp = Expect->spawn("telnet localhost")
# or die "Cannot spawn telnet: $!\n";;
my $spawn_ok;
$exp->expect($timeout,
[
qr'login: $',
sub {
$spawn_ok = 1;
my $fh = shift;
$fh->send("$username\n");
exp_continue;
}
],
[
'Password: $',
sub {
my $fh = shift;
print $fh "$password\n";
exp_continue;
}
],
[
eof =>
sub {
if ($spawn_ok) {
die "ERROR: premature EOF in login.\n";
} else {
die "ERROR: could not spawn telnet.\n";
}
}
],
[
timeout =>
sub {
die "No login.\n";
}
],
'-re', qr'[#>:] $', #' wait for shell prompt, then exit expect
);
How to expect on multiple spawned commands¶
foreach my $cmd (@list_of_commands) {
push @commands, Expect->spawn($cmd);
}
expect($timeout,
'-i', \@commands,
[
qr"pattern", # find this pattern in output of all commands
sub {
my $obj = shift; # object that matched
print $obj "something\n";
exp_continue; # we don't want to terminate the expect call
}
],
'-i', $some_other_command,
[
"some other pattern",
sub {
my ($obj, $parmref) = @_;
# ...
# now we exit the expect command
},
\$parm
],
);
How to propagate terminal sizes¶
my $exp = new Expect;
$exp->slave->clone_winsize_from(\*STDIN);
$exp->spawn("ssh somehost);
$SIG{WINCH} = \&winch;
sub winch {
$exp->slave->clone_winsize_from(\*STDIN);
kill WINCH => $exp->pid if $exp->pid;
$SIG{WINCH} = \&winch;
}
$exp->interact();
HOMEPAGE¶
http://sourceforge.net/projects/expectperl/
MAILING LISTS¶
There are two mailing lists available, expectperl-announce and
expectperl-discuss, at
http://lists.sourceforge.net/lists/listinfo/expectperl-announce
and
http://lists.sourceforge.net/lists/listinfo/expectperl-discuss
BUG TRACKING¶
You can use the CPAN Request Tracker
http://rt.cpan.org/ and submit new bugs
under
http://rt.cpan.org/Ticket/Create.html?Queue=Expect
AUTHORS¶
(c) 1997 Austin Schutz <
ASchutz@users.sourceforge.net> (retired)
expect() interface & functionality enhancements (c) 1999-2006 Roland
Giersig.
This module is now maintained by Roland Giersig <
RGiersig@cpan.org>
LICENSE¶
This module can be used under the same terms as Perl.
DISCLAIMER¶
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
In other words: Use at your own risk. Provided as is. Your mileage may vary.
Read the source, Luke!
And finally, just to be sure:
Any Use of This Product, in Any Manner Whatsoever, Will Increase the Amount of
Disorder in the Universe. Although No Liability Is Implied Herein, the
Consumer Is Warned That This Process Will Ultimately Lead to the Heat Death of
the Universe.