farhan has asked for the wisdom of the Perl Monks concerning the following question:

#!/usr/bin/perl
$cmd = qx {id ahmedf};
if($cmd =~ /uid/) {
print "LDAP Ok\n";
exit 0;
}
if($cmd =~ /invalid/i) {
print "Please check LDAP\n";
exit 2;
}
If test user is there I get proper message "LDAP OK" but if test user is not there I get system message "id: invalid user name: "test" rather than message in loop, how can I get the message "Please check LDAP"

Replies are listed 'Best First'.
Re: simple Help
by ccn (Vicar) on Nov 26, 2008 at 07:39 UTC

    There are two options

    • try to redirect stderr: qx{id ahmedf 2>&1} to get error messages in $cmd
    • exit 2; without any condition after the first if block
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      Thanks mate, qx{id ahmedf 2>&1} did the trick, thanks heaps . just curious what "2>&1" does in fact
[reply]
        farhan:

        It tells the command shell to send all output from filehandle 2 (typically STDERR) to filehandle 1 (typically STDOUT). For further details, see perldoc perlop:

           qx/STRING/
   `STRING`
      A string which is (possibly) interpolated and then executed as
      a system command with "/bin/sh" or its equivalent.  Shell wild-
      cards, pipes, and redirections will be honored.  The collected
      standard output of the command is returned; standard error is
      unaffected.  In scalar...

      <<<<< SNIP >>>>>

      ...To capture a command's STDERR and STDOUT together:

         $output = `cmd 2>&1`;

        [download]
        ...roboticus
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Re: simple Help
by farhan (Novice) on Nov 26, 2008 at 09:20 UTC
    qx{id ahmedf 2>&1} did the trick, thanks heaps
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Re: simple Help
by toolic (Bishop) on Nov 26, 2008 at 16:07 UTC
    It may also be useful to check the return status of your qx command using the special variable $?. This may be a more portable solution since I do not get the same system message as you do when it fails. I get "id: test: No such user". 
    use strict;
use warnings;

my $cmd = qx{id ahmedf 2>&1};
if ($?) {
    print "Please check LDAP\n";
    exit 2;
}
elsif ($cmd =~ /uid/) {
    print "LDAP Ok\n";
    exit 0;
}

    [download]
[reply]
[d/l]
Re: simple Help
by sathiya.sw (Monk) on Nov 26, 2008 at 08:42 UTC
    use else instead of the second if statement. Then your message "please check LDAP will get printed. But system message also got printed.

[reply]
      I don't understand why you recommend eval over qx, since these two serve completely different purposes. Care to explain?

      Update: OP has changed, this posting is now irrelevant.

[reply]

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