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Ask is a grep replacement that searches entire trees by default while ignoring Subversion, Git and other VCS directories and other files that aren't your source code. Designed for code search. Where grep is a general text search tool, ack is especially for the programmer searching source code. Common tasks take fewer keystrokes.
ack is written in Perl
Usage: ack [OPTION]... PATTERN [FILES OR DIRECTORIES] Search for PATTERN in each source file in the tree from the current directory on down. If any files or directories are specified, then only those files and directories are checked. ack may also search STDIN, but only if no file or directory arguments are specified, or if one of them is "-". Default switches may be specified in ACK_OPTIONS environment variable or an .ackrc file. If you want no dependency on the environment, turn it off with --noenv. Example: ack -i select Searching: -i, --ignore-case Ignore case distinctions in PATTERN --[no]smart-case Ignore case distinctions in PATTERN, only if PATTERN contains no upper case. Ignored if -i is specified -v, --invert-match Invert match: select non-matching lines -w, --word-regexp Force PATTERN to match only whole words -Q, --literal Quote all metacharacters; PATTERN is literal Search output: --lines=NUM Only print line(s) NUM of each file -l, --files-with-matches Only print filenames containing matches -L, --files-without-matches Only print filenames with no matches --output=expr Output the evaluation of expr for each line (turns off text highlighting) -o Show only the part of a line matching PATTERN Same as --output='$&' --passthru Print all lines, whether matching or not --match PATTERN Specify PATTERN explicitly. -m, --max-count=NUM Stop searching in each file after NUM matches -1 Stop searching after one match of any kind -H, --with-filename Print the filename for each match (default: on unless explicitly searching a single file) -h, --no-filename Suppress the prefixing filename on output -c, --count Show number of lines matching per file --[no]column Show the column number of the first match -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. -C [NUM], --context[=NUM] Print NUM lines (default 2) of output context. --print0 Print null byte as separator between filenames, only works with -f, -g, -l, -L or -c. -s Suppress error messages about nonexistent or unreadable files. File presentation: --pager=COMMAND Pipes all ack output through COMMAND. For example, --pager="less -R". Ignored if output is redirected. --nopager Do not send output through a pager. Cancels any setting in ~/.ackrc, ACK_PAGER or ACK_PAGER_COLOR. --[no]heading Print a filename heading above each file's results. (default: on when used interactively) --[no]break Print a break between results from different files. (default: on when used interactively) --group Same as --heading --break --nogroup Same as --noheading --nobreak --[no]color Highlight the matching text (default: on unless output is redirected, or on Windows) --[no]colour Same as --[no]color --color-filename=COLOR --color-match=COLOR --color-lineno=COLOR Set the color for filenames, matches, and line numbers. --flush Flush output immediately, even when ack is used non-interactively (when output goes to a pipe or file). File finding: -f Only print the files selected, without searching. The PATTERN must not be specified. -g Same as -f, but only select files matching PATTERN. --sort-files Sort the found files lexically. --show-types Show which types each file has. --files-from=FILE Read the list of files to search from FILE. -x Read the list of files to search from STDIN. File inclusion/exclusion: --[no]ignore-dir=name Add/remove directory from list of ignored dirs --[no]ignore-directory=name Synonym for ignore-dir --ignore-file=filter Add filter for ignoring files -r, -R, --recurse Recurse into subdirectories (default: on) -n, --no-recurse No descending into subdirectories --[no]follow Follow symlinks. Default is off. -k, --known-types Include only files of types that ack recognizes. --type=X Include only X files, where X is a recognized filetype. --type=noX Exclude X files. See "ack --help-types" for supported filetypes. File type specification: --type-set TYPE:FILTER:FILTERARGS Files with the given FILTERARGS applied to the given FILTER are recognized as being of type TYPE. This replaces an existing definition for type TYPE. --type-add TYPE:FILTER:FILTERARGS Files with the given FILTERARGS applied to the given FILTER are recognized as being type TYPE. --type-del TYPE Removes all filters associated with TYPE. Miscellaneous: --[no]env Ignore environment variables and global ackrc files. --env is legal but redundant. --ackrc=filename Specify an ackrc file to use --ignore-ack-defaults Ignore default definitions included with ack. --create-ackrc Outputs a default ackrc for your customization to standard output. --help, -? This help --help-types Display all known types --dump Dump information on which options are loaded from which RC files --[no]filter Force ack to treat standard input as a pipe (--filter) or tty (--nofilter) --man Man page --version Display version & copyright --thpppt Bill the Cat --bar The warning admiral --cathy Chocolate! Chocolate! Chocolate! Exit status is 0 if match, 1 if no match. This is version 2.12 of ack.
Usage: ack [OPTION]... PATTERN [FILES OR DIRECTORIES] The following is the list of filetypes supported by ack. You can specify a file type with the --type=TYPE format, or the --TYPE format. For example, both --type=perl and --perl work. Note that some extensions may appear in multiple types. For example, .pod files are both Perl and Parrot. --[no]actionscript .as .mxml --[no]ada .ada .adb .ads --[no]asm .asm .s --[no]asp .asp --[no]aspx .master .ascx .asmx .aspx .svc --[no]batch .bat .cmd --[no]cc .c .h .xs --[no]cfmx .cfc .cfm .cfml --[no]clojure .clj --[no]cmake CMakeLists.txt; .cmake --[no]coffeescript .coffee --[no]cpp .cpp .cc .cxx .m .hpp .hh .h .hxx --[no]csharp .cs --[no]css .css --[no]dart .dart --[no]delphi .pas .int .dfm .nfm .dof .dpk .dproj .groupproj .bdsgroup .bdsproj --[no]elisp .el --[no]elixir .ex .exs --[no]erlang .erl .hrl --[no]fortran .f .f77 .f90 .f95 .f03 .for .ftn .fpp --[no]go .go --[no]groovy .groovy .gtmpl .gpp .grunit .gradle --[no]haskell .hs .lhs --[no]hh .h --[no]html .htm .html --[no]java .java .properties --[no]js .js --[no]json .json --[no]jsp .jsp .jspx .jhtm .jhtml --[no]less .less --[no]lisp .lisp .lsp --[no]lua .lua; first line matches /^#!.*\blua(jit)?/ --[no]make .mk; .mak; makefile; Makefile; GNUmakefile --[no]matlab .m --[no]md .mkd; .md --[no]objc .m .h --[no]objcpp .mm .h --[no]ocaml .ml .mli --[no]parrot .pir .pasm .pmc .ops .pod .pg .tg --[no]perl .pl .pm .pod .t .psgi; first line matches /^#!.*\bperl/ --[no]perltest .t --[no]php .php .phpt .php3 .php4 .php5 .phtml; first line matches /^#!.*\bphp/ --[no]plone .pt .cpt .metadata .cpy .py --[no]pmc .pmc --[no]python .py; first line matches /^#!.*\bpython/ --[no]rake Rakefile --[no]rr .R --[no]ruby .rb .rhtml .rjs .rxml .erb .rake .spec; Rakefile; first line matches /^#!.*\bruby/ --[no]rust .rs --[no]sass .sass .scss --[no]scala .scala --[no]scheme .scm .ss --[no]shell .sh .bash .csh .tcsh .ksh .zsh .fish; first line matches /^#!.*\b(?:ba|t?c|k|z|fi)?sh\b/ --[no]smalltalk .st --[no]sql .sql .ctl --[no]tcl .tcl .itcl .itk --[no]tex .tex .cls .sty --[no]textile .textile --[no]tt .tt .tt2 .ttml --[no]vb .bas .cls .frm .ctl .vb .resx --[no]verilog .v .vh .sv --[no]vhdl .vhd .vhdl --[no]vim .vim --[no]xml .xml .dtd .xsl .xslt .ent; first line matches /<[?]xml/ --[no]yaml .yaml .yml
Ack only searches the stuff that makes sense to search. Perl's regular expressions are highly optimized.
ack is pure Perl, so it runs on Windows just fine. It has no dependencies other than Perl 5. Installation is a snap.
ack searches recursively by default, while ignoring
and other VCS directories.
# Which would you rather type?
$ grep pattern $(find . -type f | grep -v '\.svn')
$ ack pattern
Since ack defaults to only searching source code, you get fewer false positives.
If you have a big project with many different languages combined, it's easy to add --perl to search only Perl files, or use --nohtml to search everything except HTML.
ack's filetype detection means more than just specifying a single file extension.
# Which would you rather type? $ grep pattern $(find . -name '*.pl' -or -name '*.pm' -or -name '*.pod' | grep -v .svn)
$ ack --perl pattern
Plus, ack does filetype detection that
find can't. ack checks the shebang lines of scripts
Since ack can know to search only, say, Ruby files with the
--ruby switch, you can also
generate a list of files in a tree with the
# List all Ruby files in the tree
$ ack -f --ruby > all-ruby-files
ack has flexible match highlighting, where you can specify the colors to use in its output.
Perl leads the programming world with its regular expressions. ack uses Perl's regular expressions, not a "Perl-compatible" subset.
You can also take advantage of Perl's match variables. For example, to generate a list of all files
#included in your C code, use this:
ack --cc '#include\s+<(.*)>' --output '$1' -h
If you know GNU grep, you know most of ack's switches, too. Word-only searching with
case-insensitive searching with
This one is sort of a joke, but sort of not. You spend hours every day searching through source code. ack makes it as quick and easy as possible to do that searching and to remove as much drudgerous typing as possible.
Defaults matter. The less typing you have to do, the better.
Installation is a snap. Try ack for yourself.
There are some tools that look like you will never replace them. One of those (for me) is grep. It does what it does very well (remarks about the shortcomings of regexen in general aside). It works reasonably well with Unicode/UTF-8 (a great opportunity to Fail Miserably for any tool, viz. a2ps).
Yet, the other day I read about ack, which claims to be "better than grep, a search tool for programmers". Woo. Better than grep? In what way?
The ack homepage lists the top ten reasons why one should use it instead of grep. Actually, it's thirteen reasons but then some are dupes. So I'd say "about ten reasons". Let's look at them in order.
- It's blazingly fast because it only searches the stuff you want searched.
Wait, how does it know what I want? A DWIM-Interface at last? Not quite. First off, ack is faster than grep for simple searches. Here's an example:$ time ack 1Jsztn-000647-SL exim_main.log >/dev/null real 0m3.463s user 0m3.280s sys 0m0.180s $ time grep -F 1Jsztn-000647-SL exim_main.log >/dev/null real 0m14.957s user 0m14.770s sys 0m0.160s
Two notes: first, yes, the file was in the page cache before I ran ack; second, I even made it easy for grep by telling it explicitly I was looking for a fixed string (not that it helped much, the same command without -F was faster by about 0.1s). Oh and for completeness, the exim logfile I searched has about two million lines and is 250M. I've run those tests ten times for each, the times shown above are typical.
So yes, for simple searches, ack is faster than grep. Let's try with a more complicated pattern, then. This time, let's use the pattern (klausman|gentoo) on the same file. Note that we have to use -E for grep to use extended regexen, which ack in turn does not need, since it (almost) always uses them. Here, grep takes its sweet time: 3:56, nearly four minutes. In contrast, ack accomplished the same task in 49 seconds (all times averaged over ten runs, then rounded to integer seconds).
As for the "being clever" side of speed, see below, points 5 and 6
- ack is pure Perl, so it runs on Windows just fine.
This isn't relevant to me, since I don't use windows for anything where I might need grep. That said, it might be a killer feature for others.
- The standalone version uses no non-standard modules, so you can put it in your ~/bin without fear.
Ok, this is not so much of a feature than a hard criterion. If I needed extra modules for the whole thing to run, that'd be a deal breaker. I already have tons of libraries, I don't need more undergrowth around my dependency tree.
- Searches recursively through directories by default, while ignoring .svn, CVS and other VCS directories.
This is a feature, yet one that wouldn't pry me away from grep: -r is there (though it distinctly feels like an afterthought). Since ack ignores a certain set of files and directories, its recursive capabilities where there from the start, making it feel more seamless.
- ack ignores most of the crap you don't want to search
To be precise:
- VCS directories
- blib, the Perl build directory
- backup files like foo~ and #foo#
- binary files, core dumps, etc.
Most of the time, I don't want to search those (and have to exclude them with grep -v from find results). Of course, this ignore-mode can be switched off with ack (-u). All that said, it sure makes command lines shorter (and easier to read and construct). Also, this is the first spot where ack's Perl-centricism shows. I don't mind, even though I prefer that other language with P.
- Ignoring .svn directories means that ack is faster than grep for searching through trees.
Dupe. See Point 5
- Lets you specify file types to search, as in --perl or --nohtml.
While at first glance, this may seem limited, ack comes with a plethora of definitions (45 if I counted correctly), so it's not as perl-centric as it may seem from the example. This feature saves command-line space (if there's such a thing), since it avoids wild find-constructs. The docs mention that --perl also checks the shebang line of files that don't have a suffix, but make no mention of the other "shipped" file type recognizers doing so.
- File-filtering capabilities usable without searching with ack -f. This lets you create lists of files of a given type.
This mostly is a consequence of the feature above. Even if it weren't there, you could simply search for "."
- Color highlighting of search results.
While I've looked upon color in shells as kinda childish for a while, I wouldn't want to miss syntax highlighting in vim, colors for ls (if they're not as sucky as the defaults we had for years) or match highlighting for grep. It's really neat to see that yes, the pattern you grepped for indeed matches what you think it does. Especially during evolutionary construction of command lines and shell scripts.
- Uses real Perl regular expressions, not a GNU subset
Again, this doesn't bother me much. I use egrep/grep -E all the time, anyway. And I'm no Perl programmer, so I don't get withdrawal symptoms every time I use another regex engine.
- Allows you to specify output using Perl's special variables
This sounds neat, yet I don't really have a use case for it. Also, my perl-fu is weak, so I probably won't use it anyway. Still, might be a killer feature for you.
The docs have an example:ack '(Mr|Mr?s)\. (Smith|Jones)' --output='$&'
- Many command-line switches are the same as in GNU grep:
Specifically mentioned are -w, -c and -l. It's always nice if you don't have to look up all the flags every time.
- Command name is 25% fewer characters to type! Save days of free-time! Heck, it's 50% shorter compared to grep -r
Okay, now we have proof that not only the ack webmaster can't count, he's also making up reasons for fun. Works for me.
Bottom line: yes, ack is an exciting new tool which partly replaces grep. That said, a drop-in replacement it ain't. While the standalone version of ack needs nothing but a perl interpreter and its standard modules, for embedded systems that may not work out (vs. the binary with no deps beside a libc). This might also be an issue if you need grep early on during boot and /usr (where your perl resides) isn't mounted yet. Also, default behaviour is divergent enough that it might yield nasty surprises if you just drop in ack instead of grep. Still, I recommend giving ack a try if you ever use grep on the command line. If you're a coder who often needs to search through working copies/checkouts, even more so.
I've written a followup on this, including some tips for day-to-day usage (and an explanation of grep's sucky performance).
René "Necoro" Neumann writes (in German, translation by me):
Stumbled across your blog entry about "ack" today. I tried it and found it to be cool :). So I created two ebuilds for it:
Google matched content
Articles from around the web about ack and searching. Let me know if there are any that should be on here.
Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers : Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism : The Iron Law of Oligarchy : Libertarian Philosophy
War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda : SE quotes : Language Design and Programming Quotes : Random IT-related quotes : Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce : Bernard Shaw : Mark Twain Quotes
Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 : Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law
Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds : Larry Wall : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS : Programming Languages History : PL/1 : Simula 67 : C : History of GCC development : Scripting Languages : Perl history : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history
The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month : How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Hater’s Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite
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Last modified: March, 12, 2019