Equivalent of Linux Grep Command

[bichonfrise74]

Hello,

I'm trying to do a simple equivalent of

grep -A1 -B1 'hello' file_name

in Perl. This basically prints the previous and the next line when the word 'hello' is found. I've done a super search and came up with the following links:

Grep - print matched line and next N lines
Emulating GNU grep -A and -B switches with perl

Both were created back in 2003 and I was wondering if there is now a more concise solution to this. I mean using the Linux 'grep' command, it is able to do it in one line which strikes me odd that it cannot be done in Perl in a concise manner.

Below is my code but again, I think it is too clunky and too long when compared to the Linux 'grep' command.

#!/usr/bin/perl

use strict;

my ($prev, $next);
while (my $line = <DATA>) {
    if ( $next ) {
        print "$line";
        $next = undef;
    }
    if ( $line =~ /hello/ ) {
        print "$prev" if defined( $prev );
        print "$line";
        $next++;
    }
    $prev = $line;
}

__DATA__
test1
test2
hello
test3
test4

Thanks in advance.

[Corion]

There is ack, which lives in App::Ack, which is considered to be even better than grep by some, because it also supports file types, recursive descent through file systems and skips VCS directories.

[thunders]

That's a reasonable start to an implementation. Any solution I can think of involve scanning the file and maintaining @before and @after buffers as you go.

Perl isn't really intended to provide one liners for every common unix command, and grep itself is a tool not a programming language, any implementation of grep in C is considerably more than one 80 character line of code.

There is a program called prep on CPAN, which is a pure perl implementation of grep. The source to that program may provide inspiration.

[CountZero]

Perl being the "glue language" par excellence, why don't you just shell out and call he Unix grep? There is no shame in relying on tried and trusted tools.

[Your Mother]

I give a hearty second to ack. Except for the times I need to do huge recursive grepping where grep's speed superiority matters ack is all I use now.

[ambrus]

cgrep: Egrep clone with function name display links to a few grep-like programs written in perl. Sure, mine is unmaintained too, and I have a page long TODO for it, but I still have it installed on my computer and use it occasionally.

[JavaFan]

Both were created back in 2003 and I was wondering if there is now a more concise solution to this.

Since 2003 there has been only one major release of Perl, and none of the new features would make mimicing grep -A1 -B1 any simpler than it already is.

[petdance]

Even if you don't want to use ack from the command line, take a look at how it handles the -A and -B flags. It's not very complex.