I did this a while ago in Timing and timing out Unix commands.

I gather from eyepopslikeamosquito's post that a pure-Perl solution that both kills the process on timeout and captures its exit status otherwise is non-trivial.

Not sure what O/S you are using. In Unix/Linux, I would be surprised to find any networking command that doesn't have a timeout option, so I would check that first. Alternatively, there is the timeout command, which would solve your problem entirely.

I gather from eyepopslikeamosquito's post that a pure-Perl solution that both kills the process on timeout and captures its exit status otherwise is non-trivial.

It is not trivial, but is is not so complex either:

# untested!
use POSIX qw(WNOHANG _exit);
use Errno qw(ECHILD);

local $SIG{CHLD} = sub {}; # this do-nothing sub ends the
                           # select below on SIGCHLD

my $pid = fork;
if (!$pid) {
    defined $pid or die "fork failed: $!";
    do { exec @cmd }; # warnings friendly!
    _exit(1);
}

my $start = time;
while (1) {
  my $rc = waitpid ($pid, WNOHANG);
  last if $rc == $pid;
  last if $rc < 0 and $! == ECHILD;
  select (undef, undef, undef, 1);
  kill INT => $pid if time > $start + $timeout;
}
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Using AnyEvent it would be even easier.

/home/fred$ result=$(perl gash.pl)
/home/fred$ echo $result
Timeout
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Problem is i need the exit code from the shell command, so i can't change the code to fork/exec

There is no such limitation when using fork/exec. The waitpid built-in lets you retrieve the exit status of the child.

update: if you want to get the output from the program, you would like to launch the process using open:

my $pid = open my $fh, '-|', @cmd or die "open failed $!";
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Ok let me explain it clearer. i've a main perl program which loops and execute commands (run's as a daemon), so when i execute with `cmd....` system and so so on i become zombies...... excample prog what i call

test.pl
#!/usr/bin/perl
$status='OK';
print $status;
1;

test2.pl
#!/usr/bin/perl
$status='124455566345';
print $status;
1;

so here i get zombies, problem is i need the print $status;
in daemon.pl, that can be ascii strings or numerics....
daemon.pl
#!/usr/bin/perl
while(1){
my $command='test1.pl or test2.pl';
my $status;
eval {
  local $SIG{ALRM} = sub { die("dead\n"); };
  alarm 2; 
  my $status=`$command`;
  alarm(0); # turn off the alarm clock
};
if($@){
  if($@ eq "dead\n"){
     $status='Timeout';
  }else{
     chomp($status);
  }
}

#do something with my $status.....


sleep(5);
}
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Using alarm to leave from `$cmd` prematurely leaves zombies as it jumps over the waitpid call inside that reaps the child process.

# untested!
my $pid = open my $out, '-|', $cmd or die "Open failed: $!";
local $INT{CHLD} = sub {};
my $fileno = fileno $out;
my $start = time;
my $str = '';
my $timedout = 0;
while (1) {
  my $v = '';
  vec($v, $fileno, 1) = 1;
  if (select($v, undef, undef, 1) > 0) {
    if (vec($v, $fileno, 1)) {
      sysread $v, $str, 1024, length $v or last;
    }
  }
  if (time - $start > $timeout) {
    $timedout = 1;
    kill INT => $pid 
}
close ($out);

print "timed out: $timedout\noutput: $str\n";
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