# two parameters:
#  cmd     - a command or reference to an array of command + arguments
#  timeout - number of seconds to wait (0 = forever)

# returns:
#  cmd exit status (-1 if timed out)
#  cmd results (STDERR and STDOUT merged into an array ref)

sub ExecCmd {
  my $cmd = shift || return(0, []);
  my $timeout = shift || 0;

  # opening a pipe creates a forked process	
  my $pid = open(my $pipe, '-|');
  return(-1, "Can't fork: $!") unless defined $pid;

  if ($pid) {
    # this code is running in the parent process

    my @result = ();

    if ($timeout) {
      my $failed = 1;
      eval {
        # set a signal to die if the timeout is reached
        local $SIG{ALRM} = sub { die "alarm\n" };
        alarm $timeout;
        @result = <$pipe>;
        alarm 0;
        $failed = 0;
      };
      return(-1, ['command timeout', @result]) if $failed;
    }
    else {
      @result = <$pipe>;
    }
    close($pipe);

    # return exit status, command output
    return ($? >> 8), \@result;
  }

  # this code is running in the forked child process

  { # skip warnings in this block
    no warnings;

    # redirect STDERR to STDOUT
    open(STDERR, '>&STDOUT');

    # exec transfers control of the process
    # to the command
    ref($cmd) eq 'ARRAY' ? exec(@$cmd) : exec($cmd);
  }

  # this code will not execute unless exec fails!
  print "Can't exec @$cmd: $!";
  exit 1;
}