#!/usr/bin/perl
#
# Grep for something and display the line and
# the N lines following the match (default 1)
# Prefix each line with the filename
# if there is more than 1 file argument
# Exit status:
# 0 - a match was found
# 1 - No match was found
# >1 - An error was encountered (even if a match was found)
use Getopt::Std;

$usage_str = <<EOT;
Usage: ngrep [-h] [-i] [-n #] [-q] pattern file1 file2 ...
-h - Suppress file names when multiple file arguments are supplied
-i - Do case-insensitive search
-n - Number of lines to display after match (default: 1)
-q - Treat pattern as a literal string instead of a regex
-r - Don't reset count if line following matched line matches
EOT
getopts('qrhin:') or die $usage_str;
die $usage_str unless @ARGV;
$pttrn = shift;
$pttrn = quotemeta $pttrn if $opt_q;
$pttrn = '(?i)' . $pttrn if $opt_i;
$pttrn = eval { qr/$pttrn/ } or die "$@$usage_str";
$n = length($opt_n) ? int($opt_n)+1 : 2;
$filename = (@ARGV > 1 and ! $opt_h) ? sub { "$ARGV: " } : sub { '' };
$SIG{__WARN__} = sub { warn $_[0]; $error = 2 };
$status = 1;
$i=0;                                                      
while (<>) {                                               
 ($status, $i) = (0, $n) if ! ($opt_r and $i) and /$pttrn/;
 $i--, print &$filename, $_ if $i;                         
 $i = 0 if eof;                                            
}                                                          
exit($error || $status);