Program Input and Output

Die

• The die command... well... dies.
• In fact, the command not only dies, but the entire Perl program being executed is immediately terminated with extreme prejudice.
• The status returned from the perl program to the shell is nonzero (the traditional Unix shell "I had an error" return).
• You can use another magic variable with die, the "$!" variable, which contains the most recent operating system error.
• Example:
  

  # Open the unix password file for reading
  $theFile = "/etc/passwd";
  unless ( open ( PASSWORD, $theFile ) ) {
      die "I can't seem to open $theFile.\nError was $!\n";
  }
  

• Example:
  

  # Open the unix password file for reading
  $theFile = "/etc/passwd";
  open ( PASSWORD, $theFile ) || die "Unable to open $theFile.\nError was $!\n";
  

• If the string argument to die does not include a trailing "\n", then the output message will include the perl script name and the line number where the "die" was invoked. If you include a trailing "\n", then this information is not included.
• You can also make it a near death experience, but not actually kill the program, with the warn directive.
• It does everything the same as the die directive, but program execution continues.
• Example:
  

  # Open the unix password file for reading
  $theFile = "/etc/passwd";
  unless ( open ( PASSWORD, $theFile ) ) {
      warn "I can't seem to open $theFile.  Continuing anyway.\n";
  }