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DESCRIPTION

grep is used for simple patterns and basic regular expressions (BREs); egrep can handle extended regular expressions (EREs). See re_format(7) for more information on regular expressions. fgrep is quicker than both grep and egrep, but can only handle fixed patterns (i.e. it does not interpret regular expressions). Patterns may consist of one or more lines, allowing any of the pattern lines to match a portion of the input.

zgrep, zegrep, and zfgrep act like grep, egrep, and fgrep, respectively, but accept input files compressed with the compress(1) or gzip(1) compression utilities.

The following options are available:

-A num, --after-context=num

Print num lines of trailing context after each match. See also the -B and -C options.

-a, --text

Treat all files as ASCII text. Normally grep will simply print “Binary file ... matches” if files contain binary characters. Use of this option forces grep to output lines matching the specified pattern.

-B num, --before-context=num

Print num lines of leading context before each match. See also the -A and -C options.

-b, --byte-offset

The offset in bytes of a matched pattern is displayed in front of the respective matched line.

-C[num, --context=num]

Print num lines of leading and trailing context surrounding each match. The default is 2 and is equivalent to -A 2 -B 2. Note: no whitespace may be given between the option and its argument.

-c, --count

Only a count of selected lines is written to standard output.

--colour=[when, --color=[when]]

Mark up the matching text with the expression stored in GREP_COLOR environment variable. The possible values of when can be `never', `always' or `auto'.

-D action, --devices=action

Specify the demanded action for devices, FIFOs and sockets. The default action is `read', which means, that they are read as if they were normal files. If the action is set to `skip', devices will be silently skipped.

-d action, --directories=action

Specify the demanded action for directories. It is `read' by default, which means that the directories are read in the same manner as normal files. Other possible values are `skip' to silently ignore the directories, and `recurse' to read them recursively, which has the same effect as the -R and -r option.

-E, --extended-regexp

Interpret pattern as an extended regular expression (i.e. force grep to behave as egrep).

-e pattern, --regexp=pattern

Specify a pattern used during the search of the input: an input line is selected if it matches any of the specified patterns. This option is most useful when multiple -e options are used to specify multiple patterns, or when a pattern begins with a dash (‘-’).

--exclude

If specified, it excludes files matching the given filename pattern from the search. Note that --exclude patterns take priority over --include patterns, and if no --include pattern is specified, all files are searched that are not excluded. Patterns are matched to the full path specified, not only to the filename component.

--exclude-dir

If -R is specified, it excludes directories matching the given filename pattern from the search. Note that --exclude-dir patterns take priority over --include-dir patterns, and if no --include-dir pattern is specified, all directories are searched that are not excluded.

-F, --fixed-strings

Interpret pattern as a set of fixed strings (i.e. force grep to behave as fgrep).

-f file, --file=file

Read one or more newline separated patterns from file. Empty pattern lines match every input line. Newlines are not considered part of a pattern. If file is empty, nothing is matched.

-G, --basic-regexp

Interpret pattern as a basic regular expression (i.e. force grep to behave as traditional grep).

-H

Always print filename headers with output lines.

-h, --no-filename

Never print filename headers (i.e. filenames) with output lines.

--help

Print a brief help message.

-I

Ignore binary files. This option is equivalent to --binary-file=without-match option.

-i, --ignore-case

Perform case insensitive matching. By default, grep is case sensitive.

--include

If specified, only files matching the given filename pattern are searched. Note that --exclude patterns take priority over --include patterns. Patterns are matched to the full path specified, not only to the filename component.

--include-dir

If -R is specified, only directories matching the given filename pattern are searched. Note that --exclude-dir patterns take priority over --include-dir patterns.

-J, --bz2decompress

Decompress the bzip2(1) compressed file before looking for the text.

-L, --files-without-match

Only the names of files not containing selected lines are written to standard output. Pathnames are listed once per file searched. If the standard input is searched, the string “(standard input)” is written.

-l, --files-with-matches

Only the names of files containing selected lines are written to standard output. grep will only search a file until a match has been found, making searches potentially less expensive. Pathnames are listed once per file searched. If the standard input is searched, the string “(standard input)” is written.

--mmap

Use mmap(2) instead of read(2) to read input, which can result in better performance under some circumstances but can cause undefined behaviour.

-m num, --max-count=num

Stop reading the file after num matches.

-n, --line-number

Each output line is preceded by its relative line number in the file, starting at line 1. The line number counter is reset for each file processed. This option is ignored if -c, -L, -l, or -q is specified.

--null

Prints a zero-byte after the file name.

-O

If -R is specified, follow symbolic links only if they were explicitly listed on the command line. The default is not to follow symbolic links.

-o, --only-matching

Prints only the matching part of the lines.

-p

If -R is specified, no symbolic links are followed. This is the default.

-q, --quiet, --silent

Quiet mode: suppress normal output. grep will only search a file until a match has been found, making searches potentially less expensive.

-R, -r, --recursive

Recursively search subdirectories listed.

-S

If -R is specified, all symbolic links are followed. The default is not to follow symbolic links.

-s, --no-messages

Silent mode. Nonexistent and unreadable files are ignored (i.e. their error messages are suppressed).

-U, --binary

Search binary files, but do not attempt to print them.

-u

This option has no effect and is provided only for compatibility with GNU grep.

-V, --version

Display version information and exit.

-v, --invert-match

Selected lines are those not matching any of the specified patterns.

-w, --word-regexp

The expression is searched for as a word (as if surrounded by ‘[[:<:]]’ and ‘[[:>:]]’; see re_format(7)).

-x, --line-regexp

Only input lines selected against an entire fixed string or regular expression are considered to be matching lines.

-y

Equivalent to -i. Obsoleted.

-Z, -z, --decompress

Force grep to behave as zgrep.

--binary-files=value

Controls searching and printing of binary files. Options are binary, the default: search binary files but do not print them; without-match: do not search binary files; and text: treat all files as text.

--context[=num]

Print num lines of leading and trailing context. The default is 2.

--line-buffered

Force output to be line buffered. By default, output is line buffered when standard output is a terminal and block buffered otherwise.

If no file arguments are specified, the standard input is used.