Please read the ack manual, which also includes the ack FAQ.

ack's command-line switches (ack --help)


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 an .ackrc file. If you want no dependency
on the environment, turn it off with --noenv.

File select actions:
  -f                            Only print the files selected, without
                                searching.  The PATTERN must not be specified.
  -g                            Same as -f, but only select files matching

File listing actions:
  -l, --files-with-matches      Print filenames with at least one match
  -L, --files-without-matches   Print filenames with no matches
  -c, --count                   Print filenames and count of matching lines

  -i, --ignore-case             Ignore case distinctions in PATTERN
  -S, --[no]smart-case          Ignore case distinctions in PATTERN,
                                only if PATTERN contains no upper case.
                                Ignored if -i or -I are specified.
  -I, --no-ignore-case          Turns on case-sensitivity in PATTERN.
                                Negates -i and --smart-case.
  -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
  --range-start PATTERN         Specify PATTERN as the start of a match range.
  --range-end PATTERN           Specify PATTERN as the end of a match range.
  --match PATTERN               Specify PATTERN explicitly. Typically omitted.
  --not PATTERN                 Specifies PATTERN that must not be found on
                                the line for a match to occur. Repeatable.

Search output:
  --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
  -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
  --[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
  --[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
  -p, --proximate=LINES         Separate match output with blank lines unless
                                they are within LINES lines from each other.
  -P, --proximate=0             Negates --proximate.
  --[no]underline               Print a line of carets under the matched text.
  --[no]color, --[no]colour     Highlight the matching text (default: on unless
                                output is redirected, or on Windows)
  --color-lineno=COLOR          Set the color for filenames, matches, line and
                                column numbers.
  --help-colors                 Show a list of possible color combinations.
  --help-rgb-colors             Show a list of advanced RGB colors.
  --flush                       Flush output immediately, even when ack is used
                                non-interactively (when output goes to a pipe or

File finding:
  --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:ARGS     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.

File type inclusion/exclusion:
  -t X, --type=X                Include only X files, where X is a filetype,
                                e.g. python, html, markdown, etc
  -T X, --type=noX              Exclude X files, where X is a filetype.
  -k, --known-types             Include only files of types that ack recognizes.
  --help-types                  Display all known types, and how they're defined.

File type specification:
  --type-set=TYPE:FILTER:ARGS   Files with the given ARGS applied to the given
                                FILTER are recognized as being of type TYPE.
                                This replaces an existing definition for TYPE.
  --type-add=TYPE:FILTER:ARGS   Files with the given ARGS applied to the given
                                FILTER are recognized as being type TYPE.
  --type-del=TYPE               Removes all filters associated with TYPE.

  --version                     Display version & copyright
  --[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.
  --dump                        Dump information on which options are loaded
                                and where they're defined.
  --[no]filter                  Force ack to treat standard input as a pipe
                                (--filter) or tty (--nofilter)
  --help                        This help
  --man                         Print the manual.
  --help-types                  Display all known types, and how they're defined.
  --help-colors                 Show a list of possible color combinations.
  --help-rgb-colors             Show a list of advanced RGB colors.
  --thpppt                      Bill the Cat
  --bar                         The warning admiral
  --cathy                       Chocolate! Chocolate! Chocolate!

Filter specifications:
    If FILTER is "ext", ARGS is a list of extensions checked against the
        file's extension.
    If FILTER is "is", ARGS must match the file's name exactly.
    If FILTER is "match", ARGS is matched as a case-insensitive regex
        against the filename.
    If FILTER is "firstlinematch", ARGS is matched as a regex the first
        line of the file's contents.

Exit status is 0 if match, 1 if no match.

ack's home page is at

The full ack manual is available by running "ack --man".

This is version v3.7.0 of ack.  Run "ack --version" for full version info.

ack's file types (ack --help-types)


The following is the list of filetypes supported by ack.  You can specify a
filetype to include with -t TYPE or --type=TYPE.  You can exclude a
filetype with -T TYPE or --type=noTYPE.

Note that some files may appear in multiple types.  For example, a file
called Rakefile is both Ruby (--type=ruby) and Rakefile (--type=rakefile).

    actionscript .as .mxml
    ada          .ada .adb .ads
    asm          .asm .s
    asp          .asp
    aspx         .master .ascx .asmx .aspx .svc
    batch        .bat .cmd
    bazel        .bzl; .bazelrc; BUILD; WORKSPACE
    cc           .c .h .xs
    cfmx         .cfc .cfm .cfml
    clojure      .clj .cljs .edn .cljc
    cmake        CMakeLists.txt; .cmake
    coffeescript .coffee
    cpp          .cpp .cc .cxx .m .hpp .hh .h .hxx
    crystal      .cr .ecr
    csharp       .cs
    css          .css
    dart         .dart
    delphi       .pas .int .dfm .nfm .dof .dpk .dproj .groupproj .bdsgroup .bdsproj
    elisp        .el
    elixir       .ex .exs
    elm          .elm
    erlang       .erl .hrl
    fortran      .f .f77 .f90 .f95 .f03 .for .ftn .fpp
    go           .go
    groovy       .groovy .gtmpl .gpp .grunit .gradle
    gsp          .gsp
    haskell      .hs .lhs
    hh           .h
    hpp          .hpp .hh .h .hxx
    html         .htm .html .xhtml
    jade         .jade
    java         .java .properties
    jenkins      Jenkinsfile
    js           .js
    json         .json
    jsp          .jsp .jspx .jspf .jhtm .jhtml
    kotlin       .kt .kts
    less         .less
    lisp         .lisp .lsp
    lua          .lua; First line matches /^#!.*\blua(jit)?/
    make         .mk; .mak; makefile; Makefile; Makefile.Debug; Makefile.Release; GNUmakefile
    markdown     .md .markdown
    matlab       .m
    objc         .m .h
    objcpp       .mm .h
    ocaml        .ml .mli .mll .mly
    perl         .pl .pm .pod .t .psgi; First line matches /^#!.*\bperl/
    perltest     .t
    php          .php .phpt .php3 .php4 .php5 .phtml; First line matches /^#!.*\bphp/
    plone        .pt .cpt .metadata .cpy .py
    pod          .pod
    powershell   .ps1 .psm1
    purescript   .purs
    pytest       Filename matches (?^i:_test[.]py$); Filename matches (?^i:^test_.*[.]py$)
    python       .py; First line matches /^#!.*\bpython/
    rake         Rakefile
    rr           .R .Rmd
    rst          .rst
    ruby         .rb .rhtml .rjs .rxml .erb .rake .spec; Rakefile; First line matches /^#!.*\bruby/
    rust         .rs
    sass         .sass .scss
    scala        .scala .sbt
    scheme       .scm .ss
    shell        .sh .bash .csh .tcsh .ksh .zsh .fish; First line matches /^#!.*\b(?:ba|t?c|k|z|fi)?sh\b/
    smalltalk    .st
    smarty       .tpl
    sql          .sql .ctl
    starlark     .star
    stylus       .styl
    svg          .svg
    swift        .swift; First line matches /^#!.*\bswift/
    tcl          .tcl .itcl .itk
    tex          .tex .cls .sty
    toml         .toml
    ts           .ts .tsx
    ttml         .tt .tt2 .ttml
    vb           .bas .cls .frm .ctl .vb .resx
    verilog      .v .vh .sv
    vhdl         .vhd .vhdl
    vim          .vim
    xml          .xml .dtd .xsd .xsl .xslt .ent .wsdl; First line matches /<[?]xml/
    yaml         .yaml .yml