Usage: ack [OPTION]... PATTERN [FILES]
Search for PATTERN in each source file in the tree from cwd on down.
If [FILES] is specified, then only those files/directories are checked.
ack may also search STDIN, but only if no FILES are specified, or if
one of FILES is "-".

Default switches may be specified in ACK_OPTIONS environment variable.

Example: ack -i select

Searching:
    -i              Ignore case distinctions
    -v              Invert match: select non-matching lines
    -w              Force PATTERN to match only whole words
    -Q              Quote all metacharacters; expr is literal

Search output:
    -l              Only print filenames containing matches
    -o              Show only the part of a line matching PATTERN
                    (turns off text highlighting)
    --output=expr   Output the evaluation of expr for each line
                    (turns off text highlighting)
    -m=NUM          Stop after NUM matches
    -H              Print the filename for each match
    -h              Suppress the prefixing filename on output
    -c, --count     Show number of lines matching per file

    --group         Group matches by file name.
                    (default: on when used interactively)
    --nogroup       One result per line, including filename, like grep
                    (default: on when the output is redirected)

    --[no]color     Highlight the matching text (default: on unless
                    output is redirected, or on Windows)

Context control:
    -B, --before-context=NUM
    -A, --after-context=NUM
    -C, --context=NUM
                    print NUM lines of context before and/or after
                    matching lines

File finding:
    -f              Only print the files found, without searching.
                    The PATTERN must not be specified.
    --sort-files    Sort the found files lexically.

File inclusion/exclusion:
    -n              No descending into subdirectories
    -a, --all       All files, regardless of extension (but still skips
                    blib, CVS, RCS, SCCS, .svn, _darcs and .git dirs)
    --perl          Include only Perl files.
    --type=perl     Include only Perl files.
    --noperl        Exclude Perl files.
    --type=noperl   Exclude Perl files.
                    See "ack --help type" for supported filetypes.
    --[no]follow    Follow symlinks.  Default is off.

Miscellaneous:
    --help          This help
    --man           Man page
    --version       Display version & copyright
    --thpppt        Bill the Cat