lib/perl5/5.6.1/SelectSaver.pm

   1 package SelectSaver;
   2
   3 =head1 NAME
   4
   5 SelectSaver - save and restore selected file handle
   6
   7 =head1 SYNOPSIS
   8
   9     use SelectSaver;
  10
  11     {
  12        my $saver = new SelectSaver(FILEHANDLE);
  13        # FILEHANDLE is selected
  14     }
  15     # previous handle is selected
  16
  17     {
  18        my $saver = new SelectSaver;
  19        # new handle may be selected, or not
  20     }
  21     # previous handle is selected
  22
  23 =head1 DESCRIPTION
  24
  25 A C<SelectSaver> object contains a reference to the file handle that
  26 was selected when it was created.  If its C<new> method gets an extra
  27 parameter, then that parameter is selected; otherwise, the selected
  28 file handle remains unchanged.
  29
  30 When a C<SelectSaver> is destroyed, it re-selects the file handle
  31 that was selected when it was created.
  32
  33 =cut
  34
  35 require 5.000;
  36 use Carp;
  37 use Symbol;
  38
  39 sub new {
  40     @_ >= 1 && @_ <= 2 or croak 'usage: new SelectSaver [FILEHANDLE]';
  41     my $fh = select;
  42     my $self = bless [$fh], $_[0];
  43     select qualify($_[1], caller) if @_ > 1;
  44     $self;
  45 }
  46
  47 sub DESTROY {
  48     my $this = $_[0];
  49     select $$this[0];
  50 }
  51
  52 1;