expect.pod

测试中用于交互的一个脚本.在自动化脚本中会用得到.希望对您有帮助.

=head2 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.


=head2 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 L<Net::FTP> or C<ncftp> (http://www.ncftp.org).  You don't use
a screwdriver to hammer in your nails either, or do you?


=head2 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 L<perlthrtut>:

  "Thinking of mixing fork() and threads?  Please lie down and wait until the feeling passes."


=head2 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);


=head2 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 C<(?-m)> inside the regexp
(you need perl5.00503 or later for that).


=head2 How can I expect on multiple spawned commands?

You can use the B<-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 B<-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.


=head2 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 C<-a>' and send me the
results and I'll see what I can deduce from that.


=head2 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?


=head2 Ok, so now how do I get what was read on the handle?

  $read = $process->before();


=head2  Where's IO::Pty?

Find it on CPAN as IO-Tty, which provides both.


=head2 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.


=head2 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().


=head2 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));


=head2 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.


=head2 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 L<ssh-keygen>).

=head2 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!]


=head2 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.


=head2 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');


=head1 Source Examples


=head2 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
	      );


=head2 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
	 ],
	);


=head2 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();



=head1 HOMEPAGE

http://sourceforge.net/projects/expectperl/


=head1 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


=head1 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


=head1 AUTHORS

(c) 1997 Austin Schutz E<lt>F<[e-mail]>E<gt> (retired)

expect() interface & functionality enhancements (c) 1999-2006 Roland Giersig.

This module is now maintained by Roland Giersig E<lt>F<[e-mail]>E<gt>


=head1 LICENSE

This module can be used under the same terms as Perl.


=head1 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.

=cut