---
name: "Expect_FAQ"
section: "3pm"
platform: "linux"
package: "libexpect-perl"
version: "1.11-4"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/Expect_FAQ"
---

# Expect\_FAQ(3pm)

Expect.pm - 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\
 **Can I use this module with ActivePerl on Windows?** I don't know.  Probably not.  There is no native support for ptys available under Windows.  On the other hand, Cygwin (http://sourceware.cygnus.com) promises to provide POSIX ptys for NT, so it should be possible to run Expect.pm under Cygwin. The Tcl/Expect homepage at http://expect.nist.gov gives two links to porting projects that might be of interest (one being DejaGnu on Cygwin).\
 **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;
```

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... :-)\
 **I want to log the whole session to a file.** Use

```
  $exp->log_file("filename");
```

or

```
  $exp->log_file($filehandle);
```

to start logging.  Note that the log is appended 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!** \[You're on HP-UX, right?\]  Well, pty handling is really a black magic, as it is extremely system dependend.  I'm thinking about stealing the pty stuff from Tcl/Expect (Hi, Don!), as that code looks much more mature than what gets done in Expect and/or IO::\[TP\]ty. Please be patient, this may take a while...\
 **How to automate login**

```
  $obj->expect($timeout,
               [
                qr'login: $',
                sub {
                  my $fh = shift;
                  print $fh "$username\r"; exp_continue;
                }
               ],
               [
                'Password: $',
                sub {
                  my $fh = shift;
                  print $fh "$password\r"; exp_continue;
                }
               ],
               [
                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, new Expect $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\r";
            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
         ],
        );
```