[Omaha.pm] SAMPLE: Timed execute of external command with timeout.

["Daniel Linder" <dan@linder.org>]

I thought I would thrown this out to the world incase anyone needs this in
the future.  Might help those of us who "Google" though new
challenges... :-)

Months ago I wrote a script that ran an external program and parsed the
output for errors.  Unfortunatly, one of the errors that I did not
anticipate was the external program hanging forever.  The usual
     $result = `/path/to/cmd`;
hung and never returned -- thus the script never completed.

I ended up writing this subroutine to call the command with a timeout
window defined.
example:
     ($TimeoutStatus, $CmdResult) =
timedexec(90,"/path/to/cmd");
This will call the program "command" and wait 90 seconds for it
to complete.  The returned value in $TimeoutStatus will be 0(success)
or 1(failure).  The value in $CmdResult will be the text output
returned by the command (to stdout).

Dan

sub timedexec {
# timedexec : This subroutine will run a command within a specified time
#            
window (in seconds).
# RETURNS : Returns an array of two elements:
#  Success : first element is 0
#            second
element is the text returned by the command.
#  Failure : first element is 1
#            second
element is empty.
#
        my $alarm=shift;
        my $CMD=shift;
        my $result = "";
        my $status = 0;

        eval {
               
local $SIG{ALRM} = sub { die "alarm\n" }; # \n required
               
alarm $alarm;
               
$result = `$CMD`;
               
alarm 0;
        };
        die if $@ && $@ ne
"alarm\n";       # propagate
errors
        if ($@) {
               
# timed out : return the error code.
               
$status=1;
               
$result="";
        }
        else {
               
# didn't time out : return a success code.
               
$status=0;
        }

        return ($status, $result);
}



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