Shell Programming and Scripting

sub my_fork {
  my $cmd = $_[0];
  my $pid;

 FORK: {
    if ($pid = fork) {
    return $pid;
    } elsif (defined $pid) {
    log_message("------------$cmd output BEGIN-------------");
    my $ret = system($cmd) ;
        if($ret !=0){
            print "$cmd not successful\n";
            log_and_exit("$cmd not successful",16) ;
    }
        else{
            my @output = `$cmd`;
            log_message(@output);
    #       log_message("------------$cmd output END---------------");
            exit 0;
        }
    } elsif ($! =~ /No more process/) {
    # EAGAIN, supposedly recoverable fork error
    sleep 5;
    redo FORK;
    } else {
    # weird fork error
    log_and_exit("Can't fork: $!\n",$failure);
    }
  }
}

sub execute_command_rc {
    my $expectedrc = $_[0];
    my $command = $_[1];
    my $pid = my_fork($command);
    my $returned_pid = waitpid($pid,0);
    my $status = $?;
    log_and_exit("no child procs to collect?????",$failure) if ($returned_pid == -1);
    log_and_exit("returned pid: $returned_pid should have been $pid",$failure)
    if ($returned_pid != $pid);
    my $exit_value = $status >> 8;
    my $signal_num = $status & 127;
    my $dumped_core = $status & 128;

    log_message("$command exited with status: 16 (instead of $expectedrc)")
    if ($exit_value != $expectedrc);

    log_message("$command killed by signal: $signal_num")
    if ($signal_num);

    log_message("$command dumped core")
    if ($dumped_core);

    log_message("------------$command output END---------------");
    # emulate bash behavior. if process is killed, then return (128 | signal no.)
    return ($signal_num | 128) if ($signal_num);
    return $exit_value;
}
execute_command_rc(0,'ps -eo vsz,pid,args | sort -n');

my @output = `$cmd` ; 
if(($?>>8) !=0){ # see perlvar manpage (CHILD_ERROR) 
    print "$cmd not successful\n"; 
    log_and_exit("$cmd not successful",16) ;     
} else { 
    log_message(@output);     
    #       log_message("------------$cmd output END---------------");             
    exit 0;         
}