#!/usr/bin/perl

=head1 NAME

line - a program to display a specific line of a file with optional context

=head1 SYNOPSIS

B<line> S<[ -[B<I<num>>] ] B<I<num>> [ B<I<file>> ]>

=head1 DESCRIPTION

This program is a simple L<perl(1)> script that will display a specific line
of a file, with a switch to provide context in much the same fashion as
L<grep(1)>.  The first (optional) argument is the number of lines of
context.  The second option is the line number.  The third (optional)
option is the file name.  If a file name is not supplied or is "-",
STDIN is read.

=head1 AUTHOR

Steven Pritchard <F<steve@silug.org>>

=head1 SEE ALSO

perl(1), grep(1), head(1), tail(1)

=head1 NOTES

If you have any question about how this program works, read the source.
It is shorter than this documentation.

=cut

sub usage
{
    print STDERR "line [-[<num>]] <num> [<file>]\n";
    exit 0;
}

$line=shift;

if ($line=~/^-(-|\d*)$/)
{
    $context=$1;
    $line=shift;
}

&usage() if (!defined($line));

$file=shift || "-";

open(FILE, "<$file");

while (($count<$line) && ($_=<FILE>))
{
    $count++;
    if ((($count+$context)>=$line) && ($count<$line))
    {
        push(@context, $_);
    }
}

print @context;
print;
while ($context && ($_=<FILE>))
{
    $context--;
    print;
}