ack - grep-like text finder


    ack [options] PATTERN [FILE...]
    ack -f [options] [DIRECTORY...]


Ack is designed as a replacement for 99% of the uses of grep.

Ack searches the named input FILEs (or standard input if no files are named, or the file name - is given) for lines containing a match to the given PATTERN. By default, ack prints the matching lines.

Ack can also list files that would be searched, without actually searching them, to let you take advantage of ack's file-type filtering capabilities.


ack is intelligent about the files it searches. It knows about certain file types, based on both the extension on the file and, in some cases, the contents of the file. These selections can be made with the --type option.

With no file selections, ack only searches files of types that it recognizes. If you have a file called foo.wango, and ack doesn't know what a .wango file is, ack won't search it.

The -a option tells ack to select all files, regardless of type.

Some files will never be selected by ack, even with -a, including:

  • Backup files: Files ending with ~, or #*#

  • Coredumps: Files matching core.\d+


ack descends through the directory tree of the starting directories specified. However, it will ignore the shadow directories used by many version control systems, and the build directories used by the Perl MakeMaker system.

The following directories will never be descended into: _darcs, CVS, RCS, SCCS, .svn, blib, .git


ack trumps grep as an everyday tool 99% of the time, but don't throw grep away, because there are times you'll still need it.

ack only searches through files of types that it recognizes. If it can't tell what type a file is, then it won't look. If that's annoying to you, use grep.

If you truly want to search every file and every directory, ack won't do it. You'll need to rely on grep.

If you need context around your matches, use grep, but check back in on ack in the near future, because I'm adding it.


-a, --all

Operate on all files, regardless of type (but still skip directories like blib, CVS, etc.)

-c, --count

Suppress normal output; instead print a count of matching lines for each input file. If -l is in effect, it will only show the number of lines for each file that has lines matching. Without -l, some line counts may be zeroes.

--color, --nocolor

--color highlights the matching text. --nocolor supresses the color. This is on by default unless the output is redirected, or running under Windows.


Only print the files that would be searched, without actually doing any searching. PATTERN must not be specified, or it will be taken as a path to search.

--follow, --nofollow

Follow or don't follow symlinks, other than whatever starting files or directories were specified on the command line.

This is off by default.


Same as -f, but only print files that match REGEX. The entire path and filename are matched against REGEX, and REGEX is a Perl regular expression, not a shell glob.

--group, --nogroup

--group groups matches by file name with. This is the default when used interactively.

--nogroup prints one result per line, like grep. This is the default when output is redirected.

-H, --with-filename

Print the filename for each match.

-h, --no-filename

Suppress the prefixing of filenames on output when multiple files are searched.


Print a short help statement.

-i, --ignore-case

Ignore case in the search strings.

-l, --files-with-matches

Only print the filenames of matching files, instead of the matching text.

-m=NUM, --max-count=NUM

Stop reading a file after NUM matches.


Print this manual page.


No descending into subdirectories.


Show only the part of each line matching PATTERN (turns off text highlighting)


Output the evaluation of expr for each line (turns off text highlighting)


Prints all lines, whether or not they match the expression. Highlighting will still work, though, so it can be used to highlight matches while still seeing the entire file, as in:

    # Watch a log file, and highlight a certain IP address
    $ tail -f ~/access.log | ack --passthru
-Q, --literal

Quote all metacharacters. PATTERN is treated as a literal.


Specify a path to an alternate .ackrc file.


Sorts the found files lexically. Use this if you want your file listings to be deterministic between runs of ack.


Display the all-important Bill The Cat logo. Note that the exact spelling of --thpppppt is not important. It's checked against a regular expression.

--type=TYPE, --type=noTYPE

Specify the types of files to include or exclude from a search. TYPE is a filetype, like perl or xml. --type=perl can also be specified as --perl, and --type=noperl can be done as --noperl.

If a file is of both type "foo" and "bar", specifying --foo and --nobar will exclude the file, because an exclusion takes precedence over an inclusion.

Type specifications can be repeated and are ORed together.

See ack --help=types for a list of valid types.

-v, --invert-match

Invert match: select non-matching lines


Display version and copyright information.

-w, --word-regexp

Force PATTERN to match only whole words. The PATTERN is wrapped with \b metacharacters.

THE .ackrc FILE

The .ackrc file contains command-line options that are prepended to the command line before processing. Multiple options may live on multiple lines. Lines beginning with a # are ignored. A .ackrc might look like this:

    # Always sort the files

    # Always color, even if piping to a filter

ack looks in your home directory for the .ackrc. You can specify another location with the ACKRC variable, below.



Specifies the location of the .ackrc file. If this file doesn't exist, ack looks in the default location.


This variable specifies default options to be placed in front of any explicit options on the command line.


Specifies the color of the filename when it's printed in --group mode. By default, it's "bold green".

The recognized attributes are clear, reset, dark, bold, underline, underscore, blink, reverse, concealed black, red, green, yellow, blue, magenta, on_black, on_red, on_green, on_yellow, on_blue, on_magenta, on_cyan, and on_white. Case is not significant. Underline and underscore are equivalent, as are clear and reset. The color alone sets the foreground color, and on_color sets the background color.


Specifies the color of the matching text when printed in --color mode. By default, it's "black on_yellow".

See ACK_COLOR_FILENAME for the color specifications.


Vim integration

ack integrates easily with the Vim text editor. Set this in your .vimrc to use ack instead of grep:

    set grepprg=ack\ -a

That examples uses -a to search through all files, but you may use other default flags. Now you can search with ack and easily step through the results in Vim:

  :grep Dumper perllib


Note that FILES must still match valid selection rules. For example,

    ack something --perl foo.rb

will search nothing, because foo.rb is a Ruby file.


Andy Lester, <andy at>


Please report any bugs or feature requests to bug-ack at, or through the web interface at I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.


There is a list of enhancements I want to make to ack in the ack issues list at Google Code:

Yes, we want to be able to specify filetypes.

Yes, we want to display context.

Yes, we want to add support for a .ackrc file.

Please look in the issues list before requesting an enhancement. And, of course, patches are always welcome.


Support for and information about ack can be found at:


How appropriate to have acknowledgements!

Thanks to everyone who has contributed to ack in any way, including Nigel Metheringham, Gabor Szabo, Tod Hagan, Michael Hendricks, Ævar Arnfjörð Bjarmason, Piers Cawley, Stephen Steneker, Elias Lutfallah, Mark Leighton Fisher, Matt Diephouse, Christian Jaeger, Bill Sully, Bill Ricker, David Golden, Nilson Santos F. Jr, Elliot Shank, Merijn Broeren, Uwe Voelker, Rick Scott, Ask Bjørn Hansen, Jerry Gay, Will Coleda, Mike O'Regan, Slaven Rezić, Mark Stosberg, David Alan Pisoni, Adriano Ferreira, James Keenan, Leland Johnson, Ricardo Signes and Pete Krawczyk.


Copyright 2005-2007 Andy Lester, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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