README for IO::Null Time-stamp: "2000-09-22 16:00:47 MDT" [From the POD.] NAME IO::Null -- class for null filehandles SYNOPSIS use IO::Null; my $fh = IO::Null->new; print $fh "I have nothing to say\n"; # does nothing. # or: $fh->print("And I'm saying it.\n"); # ditto. # or: my $old = select($fh); print "and that is poetry / as I needed it --John Cage"; # nada! select($old); Or even: tie(*FOO, IO::Null); print FOO "Lalalalala!\n"; # does nothing. DESCRIPTION This is a class for null filehandles. Calling a constructor of this class always succeeds, returning a new null filehandle. Writing to any object of this class is always a no- operation, and returns true. Reading from any object of this class is always no- operation, and returns empty-string or empty-list, as appropriate. WHY You could say: open(NULL, '>/dev/null') || die "WHAAT?! $!"; and get a null FH that way. But not everyone is using an OS that has a /dev/null IMPLEMENTATION This is a subclass of IO::Handle. Applicable methods with subs that do nothing, and return an appropriate value. SEE ALSO the IO::Handle manpage, the perltie manpage, IO::Scalar CAVEATS * This: use IO::Null; $^W = 1; # turn on warnings tie(*FOO, IO::Null); print FOO "Lalalalala!\n"; # does nothing. untie(*FOO); has been known to produce this odd warning: untie attempted while 3 inner references still exist. and I've no idea why. * Furthermore, this: use IO::Null; $^W = 1; *FOO = IO::Null->new; print FOO "Lalalalala!\n"; # does nothing. close(FOO); emits these warnings: Filehandle main::FOO never opened. Close on unopened file . ...which are, in fact, true; the FH behind the FOO{IO} was never opened on any real filehandle. (I'd welcome anyone's (working) suggestions on how to suppress these warnings.) You get the same warnings with: use IO::Null; $^W = 1; my $fh = IO::Null->new; print $fh "Lalalalala!\n"; # does nothing. close $fh; Note that this, however: use IO::Null; $^W = 1; my $fh = IO::Null->new; $fh->print("Lalalalala!\n"); # does nothing. $fh->close(); emits no warnings. * I don't know if you can successfully untaint a null filehandle. * This: $null_fh->fileno will return a defined and nonzero number, but one you're not likely to want to use for anything. See the source. * These docs are longer than the source itself. Read the source! COPYRIGHT Copyright (c) 2000 Sean M. Burke. All rights reserved. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. AUTHOR Sean M. Burke sburke@cpan.org [end POD excerpt] PREREQUISITES This suite requires Perl 5; I've only used it under Perl 5.004, so for anything lower, you're on your own. IO::Null doesn't use any nonstandard modules. INSTALLATION You install IO::Null, as you would install any perl module library, by running these commands: perl Makefile.PL make make test make install If you want to install a private copy of IO::Null in your home directory, then you should try to produce the initial Makefile with something like this command: perl Makefile.PL LIB=~/perl Then you may need something like setenv PERLLIB "$HOME/perl" in your shell initialization file (e.g., ~/.cshrc). DOCUMENTATION POD-format documentation is included in Null.pm. POD is readable with the 'perldoc' utility. See ChangeLog for recent changes. MACPERL INSTALLATION NOTES Don't bother with the makefiles. Just make an IO directory in your MacPerl site_lib or lib directory, and move Null.pm into there. SUPPORT Questions, bug reports, useful code bits, and suggestions for IO::Null should just be sent to me at sburke@cpan.org AVAILABILITY The latest version of IO::Null is available from the Comprehensive Perl Archive Network (CPAN). Visit to find a CPAN site near you.