Current ack --help

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
  -S, --[no]smart-case          Ignore case distinctions in PATTERN,
                                only if PATTERN contains no upper case.
                                Ignored if -i or -I are specified.
  -I                            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
  --lines=NUM                   Only print line(s) NUM of each file.  No
                                pattern is matched.
  --match PATTERN               Specify PATTERN explicitly. Typically omitted.

Search output:
  -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
  -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]proximate               Separate match output with blank lines unless
                                they are on adjacent lines.
  --[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-colno=COLOR
  --color-lineno=COLOR          Set the color for filenames, matches, line and
                                column 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: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:
  --type=X                      Include only X files, where X is a recognized
                                filetype, e.g. --php, --ruby
  --type=noX                    Exclude X files, e.g. --nophp, --no-ruby.
  -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.

Miscellaneous:
  --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
  --faq                         Print the frequently asked questions
  --cookbook                    Print a list of tips and tricks for using ack
  --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 https://beyondgrep.com/

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

This is version 2.999_01 of ack.  Run "ack --version" for full version info.