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ack is a grep-like source code search tool.

The latest version of ack is v3.7.0, released 2023-02-25.

Designed for programmers with large heterogeneous trees of source code, ack is written in portable Perl 5 and takes advantage of the power of Perl's regular expressions.

What's new in ack?

New --not option

The new repeatable --not option lets you get more precise matches. If you want to search for "dogs" but not if "cats" or "fish" are on the line, use

ack dogs --not cats --not fish

Easier to understand error messages

The error message ack displays when the regex passed is invalid has been improved. The message is more readable and includes a pointer to the offending part of the regex. For example:

$ ack 'status: (open|closed|in progress'
ack: Invalid regex 'status: (open|closed|in progress'
Regex: status: (open|closed|in progress
               ^---HERE Unmatched ( in regex

New --proximate option groups matches near each other

A new option --proximate=N groups together lines of output that are within N lines of each other in the file. This is useful when looking for matches that are related to each other.

For example, these results:

    15: First match
    18: Second match
    19: Third match
    37: Fourth match

look like this with --proximate=1.

    15: First match

    18: Second match
    19: Third match

    37: Fourth match

Improved -w option

The -w option, which tells ack to only find whole-word matches, did not always work if your pattern began or ended with puncutation. ack would make guesses as to what your intent was, but it was not well-defined. Now, ack disallows regexes that begin or end with non-word characters.

This means that if you use ack -w foo:, the new ack will not allow it, whereas ack 2.x would.

Added -S as a synonym for --smart-case

For those without --smart-case always on, the -S will be easier for when you do want to use it.

Smart-case matching makes ack do a case-insensitive search unless the pattern being matched has a capital letter in it.

Added -I to force case-sensitivity

If you use --smart-case in your .ackrc, you can use -I to force case-sensitivity instead of having to use --no-smart-case (which still works).

Significant speed improvements

Run times for ack 3 compared to ack 2.22 are 30-40% faster because of removal of unused infrastructure for plugins.

How to install

ack is simple to install, via CPAN, package or simple download. Read how.

People love ack

"Every once in a while something comes along that improves an idea so much, you can't ignore it. Such a thing is Ack, the grep replacement."

Read what else people are saying.

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