ACK(1p) | User Contributed Perl Documentation | ACK(1p) |
ack - grep-like text finder
ack [options] PATTERN [FILE...] ack -f [options] [DIRECTORY...]
ack is designed as an alternative to grep for programmers.
ack searches the named input files or directories for lines containing a match to the given PATTERN. By default, ack prints the matching lines. If no FILE or DIRECTORY is given, the current directory will be searched.
PATTERN is a Perl regular expression. Perl regular expressions are commonly found in other programming languages, but for the particulars of their behavior, please consult <http://perldoc.perl.org/perlreref.html|perlreref>. If you don't know how to use regular expression but are interested in learning, you may consult <http://perldoc.perl.org/perlretut.html|perlretut>. If you do not need or want ack to use regular expressions, please see the "-Q"/"--literal" option.
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.
If files are not specified for searching, either on the command line or piped in with the "-x" option, ack delves into subdirectories selecting files for searching.
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 selection, ack searches through regular files that are not explicitly excluded by --ignore-dir and --ignore-file options, either present in ackrc files or on the command line.
The default options for ack ignore certain files and directories. These include:
Run ack with the "--dump" option to see what settings are set.
However, ack always searches the files given on the command line, no matter what type. If you tell ack to search in a coredump, it will search in a coredump.
ack descends through the directory tree of the starting directories specified. If no directories are specified, the current working directory is used. However, it will ignore the shadow directories used by many version control systems, and the build directories used by the Perl MakeMaker system. You may add or remove a directory from this list with the --[no]ignore-dir option. The option may be repeated to add/remove multiple directories from the ignore list.
For a complete list of directories that do not get searched, run "ack --dump".
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.
E.g., searching through huge files looking for regexes that can be expressed with grep syntax should be quicker with grep.
If your script or parent program uses grep "--quiet" or "--silent" or needs exit 2 on IO error, use grep.
If combined with -h (--no-filename) ack outputs only one total count.
On Windows, this option is off by default unless the Win32::Console::ANSI module is installed or the "ACK_PAGER_COLOR" environment variable is used.
This is off by default.
Note that
ack -g foo
is exactly the same as
ack -f | ack foo
This means that just as ack will not search, for example, .jpg files, "-g" will not list .jpg files either. ack is not intended to be a general-purpose file finder.
Note also that if you have "-i" in your .ackrc that the filenames to be matched will be case-insensitive as well.
This option can be combined with --color to make it easier to spot the match.
--nogroup prints one result per line, like grep. This is the default when output is redirected.
The DIRNAME must always be a simple directory name. Nested directories like foo/bar are NOT supported. You would need to specify --ignore-dir=foo and then no files from any foo directory are taken into account by ack unless given explicitly on the command line.
# search for foo and bar in given files ack file1 t/file* --match foo ack file1 t/file* --match bar
Using --pager does not suppress grouping and coloring like piping output on the command-line does.
--nopager cancels any setting in ~/.ackrc, "ACK_PAGER" or "ACK_PAGER_COLOR". No output will be sent through a pager.
# Watch a log file, and highlight a certain IP address $ tail -f ~/access.log | ack --passthru 123.45.67.89
# remove all files of type html ack -f --html --print0 | xargs -0 rm -f
-i always overrides this option.
Works with -f and -g options.
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.
Thus, for example, -w with the regular expression "ox" will not match the strings "box" or "oxen". However, if the regular expression is "(ox|ass)" then it will match those strings. Because the regular expression's first character is "(", the -w flag has no effect at the start, and because the last character is ")", it has no effect at the end.
Force PATTERN to match only whole words. The PATTERN is wrapped with "\b" metacharacters.
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 --sort-files # Always color, even if piping to another program --color # Use "less -r" as my pager --pager=less -r
Note that arguments with spaces in them do not need to be quoted, as they are not interpreted by the shell. Basically, each line in the .ackrc file is interpreted as one element of @ARGV.
ack looks in several locations for .ackrc files; the searching process is detailed in "ACKRC LOCATION SEMANTICS". These files are not considered if --noenv is specified on the command line.
ack allows you to define your own types in addition to the predefined types. This is done with command line options that are best put into an .ackrc file - then you do not have to define your types over and over again. In the following examples the options will always be shown on one command line so that they can be easily copy & pasted.
File types can be specified both with the the --type=xxx option, or the file type as an option itself. For example, if you create a filetype of "cobol", you can specify --type=cobol or simply --cobol. File types must be at least two characters long. This is why the C language is --cc and the R language is --rr.
ack --perl foo searches for foo in all perl files. ack --help=types tells you, that perl files are files ending in .pl, .pm, .pod or .t. So what if you would like to include .xs files as well when searching for --perl files? ack --type-add perl:ext:xs --perl foo does this for you. --type-add appends additional extensions to an existing type.
If you want to define a new type, or completely redefine an existing type, then use --type-set. ack --type-set eiffel:ext:e,eiffel defines the type eiffel to include files with the extensions .e or .eiffel. So to search for all eiffel files containing the word Bertrand use ack --type-set eiffel:ext:e,eiffel --eiffel Bertrand. As usual, you can also write --type=eiffel instead of --eiffel. Negation also works, so --noeiffel excludes all eiffel files from a search. Redefining also works: ack --type-set cc:ext:c,h and .xs files no longer belong to the type cc.
When defining your own types in the .ackrc file you have to use the following:
--type-set=eiffel:ext:e,eiffel
or writing on separate lines
--type-set eiffel:ext:e,eiffel
The following does NOT work in the .ackrc file:
--type-set eiffel:ext:e,eiffel
In order to see all currently defined types, use --help-types, e.g. ack --type-set backup:ext:bak --type-add perl:ext:perl --help-types
In addition to filtering based on extension (like ack 1.x allowed), ack 2 offers additional filter types. The generic syntax is --type-set TYPE:FILTER:FILTERARGS; FILTERARGS depends on the value of FILTER.
Example:
--type-set make:is:Makefile
Example:
--type-set perl:ext:pl,pm,t
Example:
--type-set make:match:/(gnu)?makefile/
Example:
--type-add perl:firstlinematch:/perl/
More filter types may be made available in the future.
For commonly-used ack options, environment variables can make life much easier. These variables are ignored if --noenv is specified on the command line.
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.
This option can also be set with --color-filename.
This option can also be set with --color-match.
See ACK_COLOR_FILENAME for the color specifications.
This option can also be set with --color-lineno.
See ACK_COLOR_FILENAME for the color specifications.
Using "ACK_PAGER" does not suppress grouping and coloring like piping output on the command-line does, except that on Windows ack will assume that "ACK_PAGER" does not support color.
"ACK_PAGER_COLOR" overrides "ACK_PAGER" if both are specified.
If you are not on Windows, you never need to use "ACK_PAGER_COLOR".
ack uses the colors available in Perl's Term::ANSIColor module, which provides the following listed values. Note that case does not matter when using these values.
black red green yellow blue magenta cyan white bright_black bright_red bright_green bright_yellow bright_blue bright_magenta bright_cyan bright_white
on_black on_red on_green on_yellow on_blue on_magenta on_cyan on_white on_bright_black on_bright_red on_bright_green on_bright_yellow on_bright_blue on_bright_magenta on_bright_cyan on_bright_white
ack integrates easily with the Vim text editor. Set this in your .vimrc to use ack instead of grep:
set grepprg=ack\ -k
That example uses "-k" to search through only files of the types ack knows about, but you may use other default flags. Now you can search with ack and easily step through the results in Vim:
:grep Dumper perllib
Many users have integrated ack into their preferred text editors. For details and links, see <https://beyondgrep.com/more-tools/>.
For greater compatibility with grep, ack in normal use returns shell return or exit code of 0 only if something is found and 1 if no match is found.
(Shell exit code 1 is "$?=256" in perl with "system" or backticks.)
The grep code 2 for errors is not used.
If "-f" or "-g" are specified, then 0 is returned if at least one file is found. If no files are found, then 1 is returned.
If ack gives you output you're not expecting, start with a few simple steps.
Your environment variables and .ackrc may be doing things you're not expecting, or forgotten you specified. Use --noenv to ignore your environment and .ackrc.
Ack's -f was originally added as a debugging tool. If ack is not finding matches you think it should find, run ack -f to see what files have been selected. You can also add the "--show-types" options to show the type of each file selected.
This lists the ackrc files that are loaded and the options loaded from them. So for example you can find a list of directories that do not get searched or where filetypes are defined.
The .ackrc is the place to put all your options you use most of the time but don't want to remember. Put all your --type-add and --type-set definitions in it. If you like --smart-case, set it there, too. I also set --sort-files there.
Ack does more than search files. "ack -f --perl" will create a list of all the Perl files in a tree, ideal for sending into xargs. For example:
# Change all "this" to "that" in all Perl files in a tree. ack -f --perl | xargs perl -p -i -e's/this/that/g'
or if you prefer:
perl -p -i -e's/this/that/g' $(ack -f --perl)
If you're searching for something with a regular expression metacharacter, most often a period in a filename or IP address, add the -Q to avoid false positives without all the backslashing. See the following example for more...
Here's one I used the other day to find trouble spots for a website visitor. The user had a problem loading troublesome.gif, so I took the access log and scanned it with ack twice.
ack -Q aa.bb.cc.dd /path/to/access.log | ack -Q -B5 troublesome.gif
The first ack finds only the lines in the Apache log for the given IP. The second finds the match on my troublesome GIF, and shows the previous five lines from the log in each case.
Following variables are useful in the expansion string:
For more details and other variables see <http://perldoc.perl.org/perlvar.html#Variables-related-to-regular-expressions|perlvar>.
This example shows how to add text around a particular pattern (in this case adding _ around word with "e")
ack2.pl "\w*e\w*" quick.txt --output="$`_$&_$'" _The_ quick brown fox jumps over the lazy dog The quick brown fox jumps _over_ the lazy dog The quick brown fox jumps over _the_ lazy dog
This shows how to pick out particular parts of a match using ( ) within regular expression.
ack '=head(\d+)\s+(.*)' --output=' $1 : $2' input file contains "=head1 NAME" output "1 : NAME"
There are ack mailing lists and a Slack channel for ack. See <https://beyondgrep.com/community/> for details.
First, take a look and see if ack is even looking at the file. ack is intelligent in what files it will search and which ones it won't, but sometimes that can be surprising.
Use the "-f" switch, with no regex, to see a list of files that ack will search for you. If your file doesn't show up in the list of files that "ack -f" shows, then ack never looks in it.
NOTE: If you're using an old ack before 2.0, it's probably because it's of a type that ack doesn't recognize. In ack 1.x, the searching behavior is driven by filetype. If ack 1.x doesn't know what kind of file it is, ack ignores the file. You can use the "--show-types" switch to show which type ack thinks each file is.
No, ack will always be read-only. Perl has a perfectly good way to do search & replace in files, using the "-i", "-p" and "-n" switches.
You can certainly use ack to select your files to update. For example, to change all "foo" to "bar" in all PHP files, you can do this from the Unix shell:
$ perl -i -p -e's/foo/bar/g' $(ack -f --php)
Yes! Please see "Defining your own types". If you think that ack should recognize a type by default, please see "ENHANCEMENTS".
Yes, I know.
The name of the program is "ack". Some packagers have called it "ack-grep" when creating packages because there's already a package out there called "ack" that has nothing to do with this ack.
I suggest you make a symlink named ack that points to ack-grep because one of the crucial benefits of ack is having a name that's so short and simple to type.
To do that, run this with sudo or as root:
ln -s /usr/bin/ack-grep /usr/bin/ack
Alternatively, you could use a shell alias:
# bash/zsh alias ack=ack-grep # csh alias ack ack-grep
Nothing. I wanted a name that was easy to type and that you could pronounce as a single syllable.
No, ack does not support regexes that match multiple lines. Doing so would require reading in the entire file at a time.
If you want to see lines near your match, use the "--A", "--B" and "--C" switches for displaying context.
ack treats command line options beginning with "+" or "-" as options; if you would like to search for these, you may prefix your search term with "--" or use the "--match" option. (However, don't forget that "+" is a regular expression metacharacter!)
The Perl language limits the repetition quantifier to 32K. You can search for ".{32767}" but not ".{32768}".
We try to remain as close to grep's behavior as possible, so when in doubt, see what grep does! If there's a mismatch in functionality there, please bring it up on the ack-users mailing list.
Ack can load its configuration from many sources. The following list specifies the sources Ack looks for configuration files; each one that is found is loaded in the order specified here, and each one overrides options set in any of the sources preceding it. (For example, if I set --sort-files in my user ackrc, and --nosort-files on the command line, the command line takes precedence)
Options are then loaded from the global ackrc. This is located at "/etc/ackrc" on Unix-like systems.
Under Windows XP and earlier, the global ackrc is at "C:\Documents and Settings\All Users\Application Data\ackrc"
Under Windows Vista/7, the global ackrc is at "C:\ProgramData\ackrc"
The "--noenv" option prevents all ackrc files from being loaded.
Options are then loaded from the user's ackrc. This is located at "$HOME/.ackrc" on Unix-like systems.
Under Windows XP and earlier, the user's ackrc is at "C:\Documents and Settings\$USER\Application Data\ackrc".
Under Windows Vista/7, the user's ackrc is at "C:\Users\$USER\AppData\Roaming\ackrc".
If you want to load a different user-level ackrc, it may be specified with the $ACKRC environment variable.
The "--noenv" option prevents all ackrc files from being loaded.
Options are then loaded from the project ackrc. The project ackrc is the first ackrc file with the name ".ackrc" or "_ackrc", first searching in the current directory, then the parent directory, then the grandparent directory, etc. This can be omitted using "--noenv".
The "--ackrc" option may be included on the command line to specify an ackrc file that can override all others. It is consulted even if "--noenv" is present.
Options are then loaded from the environment variable "ACK_OPTIONS". This can be omitted using "--noenv".
Options are then loaded from the command line.
A lot of changes were made for ack 2; here is a list of them.
Andy Lester, "<andy at petdance.com>"
Please report any bugs or feature requests to the issues list at Github: <https://github.com/beyondgrep/ack2/issues>
All enhancement requests MUST first be posted to the ack-users mailing list at <http://groups.google.com/group/ack-users>. I will not consider a request without it first getting seen by other ack users. This includes requests for new filetypes.
There is a list of enhancements I want to make to ack in the ack issues list at Github: <https://github.com/beyondgrep/ack2/issues>
Patches are always welcome, but patches with tests get the most attention.
Support for and information about ack can be found at:
<https://beyondgrep.com/>
<http://groups.google.com/group/ack-users>
<https://github.com/beyondgrep/ack2/issues>
<http://annocpan.org/dist/ack>
<http://cpanratings.perl.org/d/ack>
<http://search.cpan.org/dist/ack>
<http://metacpan.org/release/ack>
<https://github.com/beyondgrep/ack2>
How appropriate to have acknowledgements!
Thanks to everyone who has contributed to ack in any way, including Michele Campeotto, H.Merijn Brand, Duke Leto, Gerhard Poul, Ethan Mallove, Marek Kubica, Ray Donnelly, Nikolaj Schumacher, Ed Avis, Nick Morrott, Austin Chamberlin, Varadinsky, Sébastien Feugère, Jakub Wilk, Pete Houston, Stephen Thirlwall, Jonah Bishop, Chris Rebert, Denis Howe, Raúl Gundín, James McCoy, Daniel Perrett, Steven Lee, Jonathan Perret, Fraser Tweedale, Raál Gundán, Steffen Jaeckel, Stephan Hohe, Michael Beijen, Alexandr Ciornii, Christian Walde, Charles Lee, Joe McMahon, John Warwick, David Steinbrunner, Kara Martens, Volodymyr Medvid, Ron Savage, Konrad Borowski, Dale Sedivic, Michael McClimon, Andrew Black, Ralph Bodenner, Shaun Patterson, Ryan Olson, Shlomi Fish, Karen Etheridge, Olivier Mengue, Matthew Wild, Scott Kyle, Nick Hooey, Bo Borgerson, Mark Szymanski, Marq Schneider, Packy Anderson, JR Boyens, Dan Sully, Ryan Niebur, Kent Fredric, Mike Morearty, Ingmar Vanhassel, Eric Van Dewoestine, Sitaram Chamarty, Adam James, Richard Carlsson, Pedro Melo, AJ Schuster, Phil Jackson, Michael Schwern, Jan Dubois, Christopher J. Madsen, Matthew Wickline, David Dyck, Jason Porritt, Jjgod Jiang, Thomas Klausner, Uri Guttman, Peter Lewis, Kevin Riggle, Ori Avtalion, Torsten Blix, Nigel Metheringham, Gábor Szabó, 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, Pete Krawczyk and Rob Hoelz.
Copyright 2005-2018 Andy Lester.
This program is free software; you can redistribute it and/or modify it under the terms of the Artistic License v2.0.
See http://www.perlfoundation.org/artistic_license_2_0 or the LICENSE.md file that comes with the ack distribution.
2018-06-27 | perl v5.26.2 |