.\" GNU grep man page

.if !\n(.g \{\

.	if !\w|\*(lq| \{\

.		ds lq ``

.		if \w'\(lq' .ds lq "\(lq

.	\}

.	if !\w|\*(rq| \{\

.		ds rq ''

.		if \w'\(rq' .ds rq "\(rq

.	\}

.\}

.

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.el \{\

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\\$2 \(laemail: \\$1 \(ra\\$3

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.

.TH GREP 1 \*(Dt "GNU grep @VERSION@" "User Commands"

.hy 0

.

.SH NAME

grep, egrep, fgrep \- print lines matching a pattern

.

.SH SYNOPSIS

.B grep

.RI [ OPTIONS ]

.I PATTERN

.RI [ FILE .\|.\|.]

.br

.B grep

.RI [ OPTIONS ]

.B \-e

.I PATTERN

\&.\|.\|.\&

.RI [ FILE .\|.\|.]

.br

.B grep

.RI [ OPTIONS ]

.B \-f

.I FILE

\&.\|.\|.\&

.RI [ FILE .\|.\|.]

.

.SH DESCRIPTION

.B grep

searches for

.I PATTERN

in each

.IR FILE .

A

.I FILE

of

.RB "\*(lq" \- "\*(rq"

stands for standard input.

If no

.I FILE

is given, recursive searches examine the working directory,

and nonrecursive searches read standard input.

By default,

.B grep

prints the matching lines.

.PP

In addition, the variant programs

.B egrep

and

.B fgrep

are the same as

.B "grep\ \-E"

and

.BR "grep\ \-F" ,

respectively.

These variants are deprecated, but are provided for backward compatibility.

.

.SH OPTIONS

.SS "Generic Program Information"

.TP

.B \-\^\-help

Output a usage message and exit.

.TP

.BR \-V ", " \-\^\-version

Output the version number of

.B grep

and exit.

.SS "Matcher Selection"

.TP

.BR \-E ", " \-\^\-extended\-regexp

Interpret

.I PATTERN

as an extended regular expression (ERE, see below).

.TP

.BR \-F ", " \-\^\-fixed\-strings

Interpret

.I PATTERN

as a list of fixed strings (instead of regular expressions),

separated by newlines,

any of which is to be matched.

.TP

.BR \-G ", " \-\^\-basic\-regexp

Interpret

.I PATTERN

as a basic regular expression (BRE, see below).

This is the default.

.TP

.BR \-P ", " \-\^\-perl\-regexp

Interpret the pattern as a Perl-compatible regular expression (PCRE).

This is experimental and

.B "grep \-P"

may warn of unimplemented features.

.SS "Matching Control"

.TP

.BI \-e " PATTERN" "\fR,\fP \-\^\-regexp=" PATTERN

Use

.I PATTERN

as the pattern.

If this option is used multiple times or is combined with the

.B \-f

.RB ( \-\-file )

option, search for all patterns given.

This option can be used to protect a pattern beginning with \*(lq\-\*(rq.

.TP

.BI \-f " FILE" "\fR,\fP \-\^\-file=" FILE

Obtain patterns from

.IR FILE ,

one per line.

If this option is used multiple times or is combined with the

.B \-e

.RB ( \-\-regexp )

option, search for all patterns given.

The empty file contains zero patterns, and therefore matches nothing.

.TP

.BR \-i ", " \-\^\-ignore\-case

Ignore case distinctions, so that characters that differ only in case

match each other.

.TP

.BR \-v ", " \-\^\-invert\-match

Invert the sense of matching, to select non-matching lines.

.TP

.BR \-w ", " \-\^\-word\-regexp

Select only those lines containing matches that form whole words.

The test is that the matching substring must either be at the

beginning of the line, or preceded by a non-word constituent

character.

Similarly, it must be either at the end of the line

or followed by a non-word constituent character.

Word-constituent characters are letters, digits, and the underscore.

This option has no effect if

.B \-x

is also specified.

.TP

.BR \-x ", " \-\^\-line\-regexp

Select only those matches that exactly match the whole line.

For a regular expression pattern, this is like parenthesizing the

pattern and then surrounding it with

.B ^

and

.BR $ .

.TP

.B \-y

Obsolete synonym for

.BR \-i .

.SS "General Output Control"

.TP

.BR \-c ", " \-\^\-count

Suppress normal output; instead print a count of

matching lines for each input file.

With the

.BR \-v ", " \-\^\-invert\-match

option (see below), count non-matching lines.

.TP

.BR \-\^\-color [ =\fIWHEN\fP "], " \-\^\-colour [ =\fIWHEN\fP ]

Surround the matched (non-empty) strings, matching lines, context lines,

file names, line numbers, byte offsets, and separators (for fields and

groups of context lines) with escape sequences to display them in color

on the terminal.

The colors are defined by the environment variable

.BR GREP_COLORS .

The deprecated environment variable

.B GREP_COLOR

is still supported, but its setting does not have priority.

.I WHEN

is

.BR never ", " always ", or " auto .

.TP

.BR \-L ", " \-\^\-files\-without\-match

Suppress normal output; instead print the name

of each input file from which no output would

normally have been printed.

The scanning will stop on the first match.

.TP

.BR \-l ", " \-\^\-files\-with\-matches

Suppress normal output; instead print

the name of each input file from which output

would normally have been printed.

The scanning will stop on the first match.

.TP

.BI \-m " NUM" "\fR,\fP \-\^\-max\-count=" NUM

Stop reading a file after

.I NUM

matching lines.

If the input is standard input from a regular file,

and

.I NUM

matching lines are output,

.B grep

ensures that the standard input is positioned to just after the last

matching line before exiting, regardless of the presence of trailing

context lines.

This enables a calling process to resume a search.

When

.B grep

stops after

.I NUM

matching lines, it outputs any trailing context lines.

When the

.B \-c

or

.B \-\^\-count

option is also used,

.B grep

does not output a count greater than

.IR NUM .

When the

.B \-v

or

.B \-\^\-invert\-match

option is also used,

.B grep

stops after outputting

.I NUM

non-matching lines.

.TP

.BR \-o ", " \-\^\-only\-matching

Print only the matched (non-empty) parts of a matching line,

with each such part on a separate output line.

.TP

.BR \-q ", " \-\^\-quiet ", " \-\^\-silent

Quiet; do not write anything to standard output.

Exit immediately with zero status if any match is found,

even if an error was detected.

Also see the

.B \-s

or

.B \-\^\-no\-messages

option.

.TP

.BR \-s ", " \-\^\-no\-messages

Suppress error messages about nonexistent or unreadable files.

.SS "Output Line Prefix Control"

.TP

.BR \-b ", " \-\^\-byte\-offset

Print the 0-based byte offset within the input file

before each line of output.

If

.B \-o

.RB ( \-\^\-only\-matching )

is specified,

print the offset of the matching part itself.

.TP

.BR \-H ", " \-\^\-with\-filename

Print the file name for each match.

This is the default when there is more than one file to search.

.TP

.BR \-h ", " \-\^\-no\-filename

Suppress the prefixing of file names on output.

This is the default when there is only one file

(or only standard input) to search.

.TP

.BI \-\^\-label= LABEL

Display input actually coming from standard input as input coming from file

.IR LABEL .

This is especially useful when implementing tools like

.BR zgrep ,

e.g.,

.BR "gzip -cd foo.gz | grep --label=foo -H something" .

See also the

.B \-H

option.

.TP

.BR \-n ", " \-\^\-line\-number

Prefix each line of output with the 1-based line number

within its input file.

.TP

.BR \-T ", " \-\^\-initial\-tab

Make sure that the first character of actual line content lies on a

tab stop, so that the alignment of tabs looks normal.

This is useful with options that prefix their output to the actual content:

.BR \-H , \-n ,

and

.BR \-b .

In order to improve the probability that lines

from a single file will all start at the same column,

this also causes the line number and byte offset (if present)

to be printed in a minimum size field width.

.TP

.BR \-u ", " \-\^\-unix\-byte\-offsets

Report Unix-style byte offsets.

This switch causes

.B grep

to report byte offsets as if the file were a Unix-style text file,

i.e., with CR characters stripped off.

This will produce results identical to running

.B grep

on a Unix machine.

This option has no effect unless

.B \-b

option is also used;

it has no effect on platforms other than MS-DOS and MS-Windows.

.TP

.BR \-Z ", " \-\^\-null

Output a zero byte (the ASCII

.B NUL

character) instead of the character that normally follows a file name.

For example,

.B "grep \-lZ"

outputs a zero byte after each file name instead of the usual newline.

This option makes the output unambiguous, even in the presence of file

names containing unusual characters like newlines.

This option can be used with commands like

.BR "find \-print0" ,

.BR "perl \-0" ,

.BR "sort \-z" ,

and

.B "xargs \-0"

to process arbitrary file names,

even those that contain newline characters.

.SS "Context Line Control"

.TP

.BI \-A " NUM" "\fR,\fP \-\^\-after\-context=" NUM

Print

.I NUM

lines of trailing context after matching lines.

Places a line containing a group separator

.RB ( \-\^\- )

between contiguous groups of matches.

With the

.B \-o

or

.B \-\^\-only\-matching

option, this has no effect and a warning is given.

.TP

.BI \-B " NUM" "\fR,\fP \-\^\-before\-context=" NUM

Print

.I NUM

lines of leading context before matching lines.

Places a line containing a group separator

.RB ( \-\^\- )

between contiguous groups of matches.

With the

.B \-o

or

.B \-\^\-only\-matching

option, this has no effect and a warning is given.

.TP

.BI \-C " NUM" "\fR,\fP \-" NUM "\fR,\fP \-\^\-context=" NUM

Print

.I NUM

lines of output context.

Places a line containing a group separator

.RB ( \-\^\- )

between contiguous groups of matches.

With the

.B \-o

or

.B \-\^\-only\-matching

option, this has no effect and a warning is given.

.SS "File and Directory Selection"

.TP

.BR \-a ", " \-\^\-text

Process a binary file as if it were text; this is equivalent to the

.B \-\^\-binary\-files=text

option.

.TP

.BI \-\^\-binary\-files= TYPE

If a file's data or metadata

indicate that the file contains binary data,

assume that the file is of type

.IR TYPE .

Non-text bytes indicate binary data; these are either output bytes that are

improperly encoded for the current locale, or null input bytes when the

.B \-z

option is not given.

.IP

By default,

.I TYPE

is

.BR binary ,

and when

.B grep

discovers that a file is binary it suppresses any further output, and

instead outputs either a one-line message saying that a binary file

matches, or no message if there is no match.

.IP

If

.I TYPE

is

.BR without-match ,

when

.B grep

discovers that a file is binary it assumes that the rest of the file

does not match; this is equivalent to the

.B \-I

option.

.IP

If

.I TYPE

is

.BR text ,

.B grep

processes a binary file as if it were text; this is equivalent to the

.B \-a

option.

.IP

When

.I type

is

.BR binary ,

.B grep

may treat non-text bytes as line terminators even without the

.B \-z

option.  This means choosing

.B binary

versus

.B text

can affect whether a pattern matches a file.  For

example, when

.I type

is

.B binary

the pattern

.B q$ might

match

.B q

immediately followed by a null byte, even though this

is not matched when

.I type

is

.BR text .

Conversely, when

.I type

is

.B binary

the pattern

.B .\&

(period) might not match a null byte.

.IP

.I Warning:

The

.B \-a

option might output binary garbage,

which can have nasty side effects if the output is a terminal and if the

terminal driver interprets some of it as commands.

On the other hand, when reading files whose text encodings are

unknown, it can be helpful to use

.B \-a

or to set

.B LC_ALL='C'

in the environment, in order to find more matches even if the matches

are unsafe for direct display.

.TP

.BI \-D " ACTION" "\fR,\fP \-\^\-devices=" ACTION

If an input file is a device, FIFO or socket, use

.I ACTION

to process it.

By default,

.I ACTION

is

.BR read ,

which means that devices are read just as if they were ordinary files.

If

.I ACTION

is

.BR skip ,

devices are silently skipped.

.TP

.BI \-d " ACTION" "\fR,\fP \-\^\-directories=" ACTION

If an input file is a directory, use

.I ACTION

to process it.

By default,

.I ACTION

is

.BR read ,

i.e., read directories just as if they were ordinary files.

If

.I ACTION

is

.BR skip ,

silently skip directories.

If

.I ACTION

is

.BR recurse ,

read all files under each directory, recursively,

following symbolic links only if they are on the command line.

This is equivalent to the

.B \-r

option.

.TP

.BI \-\^\-exclude= GLOB

Skip any command-line file with a name suffix that matches the pattern

.IR GLOB ,

using wildcard matching; a name suffix is either the whole

name, or any suffix starting after a

.B /

and before a +non-\fB/\fP.

When searching recursively, skip any subfile whose base name matches

.IR GLOB ;

the base name is the part after the last

.BR / .

A pattern can use

.BR * ,

.BR ? ,

and

.BR [ ... ]

as wildcards, and

.B \e

to quote a wildcard or backslash character literally.

.TP

.BI \-\^\-exclude-from= FILE

Skip files whose base name matches any of the file-name globs read from

.I FILE

(using wildcard matching as described under

.BR \-\^\-exclude ).

.TP

.BI \-\^\-exclude-dir= GLOB

Skip any command-line directory with a name suffix that matches the

pattern

.IR GLOB .

When searching recursively, skip any subdirectory

whose base name matches

.IR GLOB .

Ignore any redundant trailing slashes in

.IR GLOB .

.TP

.BR \-I

Process a binary file as if it did not contain matching data; this is

equivalent to the

.B \-\^\-binary\-files=without-match

option.

.TP

.BI \-\^\-include= GLOB

Search only files whose base name matches

.I GLOB

(using wildcard matching as described under

.BR \-\^\-exclude ).

.TP

.BR \-r ", " \-\^\-recursive

Read all files under each directory, recursively,

following symbolic links only if they are on the command line.

Note that if no file operand is given, grep searches the working directory.

This is equivalent to the

.B "\-d recurse"

option.

.TP

.BR \-R ", " \-\^\-dereference\-recursive

Read all files under each directory, recursively.

Follow all symbolic links, unlike

.BR \-r .

.SS "Other Options"

.TP

.BR \-\^\-line\-buffered

Use line buffering on output.

This can cause a performance penalty.

.TP

.BR \-U ", " \-\^\-binary

Treat the file(s) as binary.

By default, under MS-DOS and MS-Windows,

.BR grep

guesses whether a file is text or binary as described for the

.B \-\^\-binary\-files

option.

If

.BR grep

decides the file is a text file, it strips the CR characters from the

original file contents (to make regular expressions with

.B ^

and

.B $

work correctly).

Specifying

.B \-U

overrules this guesswork, causing all files to be read and passed to the

matching mechanism verbatim; if the file is a text file with CR/LF

pairs at the end of each line, this will cause some regular

expressions to fail.

This option has no effect on platforms

other than MS-DOS and MS-Windows.

.TP

.BR \-z ", " \-\^\-null\-data

Treat input and output data as sequences of lines, each terminated by

a zero byte (the ASCII NUL character) instead of a newline.

Like the

.B \-Z

or

.B \-\^\-null

option, this option can be used with commands like

.B sort -z

to process arbitrary file names.

.

.SH "REGULAR EXPRESSIONS"

A regular expression is a pattern that describes a set of strings.

Regular expressions are constructed analogously to arithmetic

expressions, by using various operators to combine smaller expressions.

.PP

.B grep

understands three different versions of regular expression syntax:

\*(lqbasic\*(rq (BRE), \*(lqextended\*(rq (ERE) and \*(lqperl\*(rq (PCRE).

In GNU

.B grep

there is no difference in available functionality between basic and

extended syntaxes.

In other implementations, basic regular expressions are less powerful.

The following description applies to extended regular expressions;

differences for basic regular expressions are summarized afterwards.

Perl-compatible regular expressions give additional functionality, and are

documented in pcresyntax(3) and pcrepattern(3), but work only if

PCRE is available in the system.

.PP

The fundamental building blocks are the regular expressions

that match a single character.

Most characters, including all letters and digits,

are regular expressions that match themselves.

Any meta-character with special meaning

may be quoted by preceding it with a backslash.

.PP

The period

.B .\&

matches any single character.

.SS "Character Classes and Bracket Expressions"

A

.I "bracket expression"

is a list of characters enclosed by

.B [

and

.BR ] .

It matches any single

character in that list; if the first character of the list

is the caret

.B ^

then it matches any character

.I not

in the list.

For example, the regular expression

.B [0123456789]

matches any single digit.

.PP

Within a bracket expression, a

.I "range expression"

consists of two characters separated by a hyphen.

It matches any single character that sorts between the two characters,

inclusive, using the locale's collating sequence and character set.

For example, in the default C locale,

.B [a\-d]

is equivalent to

.BR [abcd] .

Many locales sort characters in dictionary order, and in these locales

.B [a\-d]

is typically not equivalent to

.BR [abcd] ;

it might be equivalent to

.BR [aBbCcDd] ,

for example.

To obtain the traditional interpretation of bracket expressions,

you can use the C locale by setting the

.B LC_ALL

environment variable to the value

.BR C .

.PP

Finally, certain named classes of characters are predefined within

bracket expressions, as follows.

Their names are self explanatory, and they are

.BR [:alnum:] ,

.BR [:alpha:] ,

.BR [:cntrl:] ,

.BR [:digit:] ,

.BR [:graph:] ,

.BR [:lower:] ,

.BR [:print:] ,

.BR [:punct:] ,

.BR [:space:] ,

.BR [:upper:] ,

and

.BR [:xdigit:].

For example,

.B [[:alnum:]]

means the character class of numbers and

letters in the current locale.

In the C locale and ASCII

character set encoding, this is the same as

.BR [0\-9A\-Za\-z] .

(Note that the brackets in these class names are part of the symbolic

names, and must be included in addition to the brackets delimiting

the bracket expression.)

Most meta-characters lose their special meaning inside bracket expressions.

To include a literal

.B ]

place it first in the list.

Similarly, to include a literal

.B ^

place it anywhere but first.

Finally, to include a literal

.B \-

place it last.

.SS Anchoring

The caret

.B ^

and the dollar sign

.B $

are meta-characters that respectively match the empty string at the

beginning and end of a line.

.SS "The Backslash Character and Special Expressions"

The symbols

.B \e<

and

.B \e>

respectively match the empty string at the beginning and end of a word.

The symbol

.B \eb

matches the empty string at the edge of a word,

and

.B \eB

matches the empty string provided it's

.I not

at the edge of a word.

The symbol

.B \ew

is a synonym for

.B [_[:alnum:]]

and

.B \eW

is a synonym for

.BR [^_[:alnum:]] .

.SS Repetition

A regular expression may be followed by one of several repetition operators:

.PD 0

.TP

.B ?

The preceding item is optional and matched at most once.

.TP

.B *

The preceding item will be matched zero or more times.

.TP

.B +

The preceding item will be matched one or more times.

.TP

.BI { n }

The preceding item is matched exactly

.I n

times.

.TP

.BI { n ,}

The preceding item is matched

.I n

or more times.

.TP

.BI {, m }

The preceding item is matched at most

.I m

times.

This is a GNU extension.

.TP

.BI { n , m }

The preceding item is matched at least

.I n

times, but not more than

.I m

times.

.PD

.SS Concatenation

Two regular expressions may be concatenated; the resulting

regular expression matches any string formed by concatenating

two substrings that respectively match the concatenated

expressions.

.SS Alternation

Two regular expressions may be joined by the infix operator

.BR | ;

the resulting regular expression matches any string matching

either alternate expression.

.SS Precedence

Repetition takes precedence over concatenation, which in turn

takes precedence over alternation.

A whole expression may be enclosed in parentheses

to override these precedence rules and form a subexpression.

.SS "Back References and Subexpressions"

The back-reference

.BI \e n\c

\&, where

.I n

is a single digit, matches the substring

previously matched by the

.IR n th

parenthesized subexpression of the regular expression.

.SS "Basic vs Extended Regular Expressions"

In basic regular expressions the meta-characters

.BR ? ,

.BR + ,

.BR { ,

.BR | ,

.BR ( ,

and

.BR )

lose their special meaning; instead use the backslashed

versions

.BR \e? ,

.BR \e+ ,

.BR \e{ ,

.BR \e| ,

.BR \e( ,

and

.BR \e) .

.

.SH "ENVIRONMENT VARIABLES"

The behavior of

.B grep

is affected by the following environment variables.

.PP

The locale for category

.BI LC_ foo

is specified by examining the three environment variables

.BR LC_ALL ,

.BR LC_\fIfoo\fP ,

.BR LANG ,

in that order.

The first of these variables that is set specifies the locale.

For example, if

.B LC_ALL

is not set, but

.B LC_MESSAGES

is set to

.BR pt_BR ,

then the Brazilian Portuguese locale is used for the

.B LC_MESSAGES

category.

The C locale is used if none of these environment variables are set,

if the locale catalog is not installed, or if

.B grep

was not compiled with national language support (NLS).

The shell command

.B "locale \-a"

lists locales that are currently available.

.TP

.B GREP_OPTIONS

This variable specifies default options

to be placed in front of any explicit options.

As this causes problems when writing portable scripts,

this feature will be removed in a future release of

.BR grep ,

and

.B grep

warns if it is used.

Please use an alias or script instead.

.TP

.B GREP_COLOR

This variable specifies the color used to highlight matched (non-empty) text.

It is deprecated in favor of

.BR GREP_COLORS ,

but still supported.

The

.BR mt ,

.BR ms ,

and

.B mc

capabilities of

.B GREP_COLORS

have priority over it.

It can only specify the color used to highlight

the matching non-empty text in any matching line

(a selected line when the

.B -v

command-line option is omitted,

or a context line when

.B -v

is specified).

The default is

.BR 01;31 ,