Program Input and Output

Backquotes

• system makes no attempt to capture the output of your executed command, which makes it of limited utility.
• The backquotes construct allows you to execute a command, and capture the results of that command (stdout) to a scalar variable.
• This variables contents may then be used for further processing.
• Example:
  

  # Find out if $userName is on the system
  
  $userList = `who | grep $userName`;
  if ( defined( $userList ){
      print "$userName is logged in\n";
  }
  

• Using the backquote in an array context returns each resulting line from the process as a seperate array entry.
• If you wish to capture both standard out and standard error from the launched process, use the normal shell construct 2>&1 .
• Example:
  

  $userList = `who | grep $userName 2>&1`;