#!/usr/bin/perl -T -w
#
# $Id: slow-filter,v 1.2 2003/10/07 00:41:07 suter Exp $
# Copyright (C) 1998,2003 Mark Suter <suter@humbug.org.au>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#
# [MJS 29 Jul 1998] Original version.
# [MJS 22 Mar 2003] Re-worked to use Getopt::Long and Pod::Usage

use strict;
use Getopt::Long;
use Pod::Usage;

$ENV{'PATH'} = '/bin:/usr/bin';
my %opt = (man => 0, help => 0, block => 8, delay => 100);
GetOptions(\%opt, "man", "help", "block", "delay") or pod2usage(0);
$opt{man} and pod2usage(-exitval => 0, -verbose => 2);
$opt{help} and pod2usage(0);

my ($len, $buf, $offset, $written);
while($len = sysread STDIN, $buf, $opt{block}) {
    if (!defined $len) {
	next if $! =~ /^Interrupted/;
	die "System read error: $!\n";
    }
    $offset = 0;
    while ($len) {    # Handle partial writes.
	$written = syswrite STDOUT, $buf, $len, $offset;
	die "System write error: $!\n" unless defined $written;
	$len -= $written;
	$offset += $written;
    };
    select undef, undef, undef, ($opt{delay} / 1000);    # Sleep for $opt{delay} ms.
}

__END__

=head1 NAME

slow-filter - A "slow" version of cat

=head1 SYNOPSIS

slow-filter [ --block <octets> ] [ --delay <ms> ]

=head1 OPTIONS

=over 8

=item B<--block>

Number of octets to read in each sysread.

=item B<--delay>

Delay in milliseconds between reads.

=item B<--man>

Print the manual page and exit.

=item B<--help>

Print a brief help message and exit.

=back

=head1 DESCRIPTION

B<This program> is a simple filter based on code from page 231 of
_Programming Perl_, under the summary of 'syswrite'.  It will 
delay its output according to the paramaters provided.

=head1 EXIT CODES

If B<this program> exits with a zero exit status and the correct
output is on standard output.  Nothing else is ever printed to
standard error.

B<This program> will exit with a non-zero exit status if there
was a fatal error.  Both fatal and non-fatal errors will cause
output on standard error.

=head1 AUTHOR

Mark Suter E<lt>F<suter@humbug.org.au>E<gt>

=head1 COPYRIGHT

Copyright (C) 1998,2003 Mark Suter E<lt>F<suter@humbug.org.au>E<gt>

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
or from the following webpage.

    http://www.gnu.org/licenses/gpl.txt

=cut