How to run a user-supplied command in an infinite loop in a perl script, till user aborts it?

I need to run a command till the system I'm testing fails, or I abort the script. The command I need to run may开发者_运维技巧 vary, so I'm taking it as a command-line argument in quotes. But I can't seem to be able to run a command-line argument using the system command. Here's what I tried so far (edited my attempt with the script that @Cfreak provided, even with which I see the same issue):

#!/usr/bin/perl


while(1)
{
    print "Iteration #: $count\n";
    $retval = system ($ARGV[1]);
    if( $retval != 0 ) {
        print "System call $ARGV[1] failed with code $retval\n";
    }
    $count++;
}

If I do ./run ls

I see the following prints:

System call  failed with code 65280
Iteration #: 1
System call  failed with code 65280
Iteration #: 2

What am i doing wrong here ?

I believe that you want $ARGV[0] and not $ARGV[1]. You might also want to check to be sure that $ARGV[0] is present.

if( 0 > $#ARGV )
{
  print "No command\n";
}
else
{
  while(1)
  {
    print "$count\n";
    my $ret = system( "ARGV[0]" );
    if( 0 != $ret )
    {
      print "<$ARGV[0] failed with $ret\n";
      exit;
    }
    $count++;
  }
}

You have single quotes around your argument to system. You don't need quotes at all (though double quotes would work)

Really you should also check the return value of the system call. It should return 0 if the call succeeds:

while(1)
{
    print "Iteration #: $count\n";
    $retval = system ($ARGV[1]);
    if( $retval != 0 ) {
         print "System call $ARGV[1] failed with code $retval\n";
    }
    $count++;
}

If you want to stop the script when the code fails then just use last:

while(1)
{
    print "Iteration #: $count\n";
    $retval = system ($ARGV[1]);
    if( $retval != 0 ) {
         print "System call $ARGV[1] failed with code $retval\n";
         last; # will break out of the loop
    }
    $count++;
}

65280 == 0xFF00, so the command did run (0xFF00 != -1), it did not die from a signal (0xFF00 & 0x7F == 0), and exited with exit code of 255 (0xFF00 >> 8 == 0xFF == 255).

So I guess you should start by checking what command you ran. Well, according to your own output, the empty string! Perhaps you want $ARGV[0] instead of $ARGV[1]?

Use use strict; use warnings;!!! It would have avoided this entire problem.