Program Input and Output

Processes as Filehandles

• It is also possible for a perl program to interact with a process.
• You can open a process just like you open a file, and read or write it just as you read or write a file.
• Simply use the "|" symbol with the open command, then treat the filehandle like normal.
• Example:
  

  # Find out who is on the system
  open(WHOPROC, "who |");
  while ( $nextUser = <WHOPROC> ) {
      print "$nextUser\n";
  }
  

• You can also write to a process
• Example:
  

  # Print who is on the system
  open(WHOPROC, "who |");
  open(PRINTER, "| lpr");
  while ( $nextUser = <WHOPROC> ) {
      print PRINTER "$nextUser\n";
  }
  
  close(WHOPROC);
  close(PRINTER);