grep searches for lines matching a pattern.
This document was produced for version 2.5.3 of gnu grep.
grep searches the input files for lines containing a match to a given pattern list. When it finds a match in a line, it copies the line to standard output (by default), or produces whatever other sort of output you have requested with options.
Though grep expects to do the matching on text, it has no limits on input line length other than available memory, and it can match arbitrary characters within a line. If the final byte of an input file is not a newline, grep silently supplies one. Since newline is also a separator for the list of patterns, there is no way to match newline characters in a text.
The general synopsis of the grep command line is
grep options pattern input_file_names
There can be zero or more options. pattern will only be seen as such (and not as an input_file_name) if it wasn't already specified within options (by using the ‘-e pattern’ or ‘-f file’ options). There can be zero or more input_file_names.
grep comes with a rich set of options: some from posix.2 and some being gnu extensions. Long option names are always a gnu extension, even for options that are from posix specifications. Options that are specified by posix, under their short names, are explicitly marked as such to facilitate posix-portable programming. A few option names are provided for compatibility with older or more exotic implementations.
Several additional options control which variant of the grep matching engine is used. See grep Programs.
while grep -m 1 PATTERN
do
echo xxxx
done < FILE
But the following probably will not work because a pipe is not a regular file:
# This probably will not work.
cat FILE |
while grep -m 1 PATTERN
do
echo xxxx
done
When grep stops after num matching lines,
it outputs any trailing context lines.
Since context does not include matching lines,
grep will stop when it encounters another matching line.
When the ‘-c’ or ‘--count’ option is also used,
grep does not output a count greater than num.
When the ‘-v’ or ‘--invert-match’ option is also used,
grep stops after outputting num non-matching lines.
When several prefix fields are to be output, the order is always file name, line number, and byte offset, regardless of the order in which these options were specified.
gzip -cd foo.gz | grep --label=foo something
CR characters that were stripped.
This will produce results identical
to running grep on a Unix machine.
This option has no effect unless the ‘-b’ option is also used;
it has no effect on platforms other than ms-dos and ms-Windows.
NUL character)
instead of the character that normally follows a file name.
For example,
‘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
‘find -print0’, ‘perl -0’, ‘sort -z’, and ‘xargs -0’
to process arbitrary file names,
even those that contain newline characters.
Regardless of how these options are set, grep will never print any given line more than once. If the ‘-o’ or ‘--only-matching’ option is specified, these options have no effect and a warning is given upon their use.
Matching lines normally use ‘:’ as a separator between prefix fields and actual line content. Context (i.e., non-matching) lines use ‘-’ instead. When no context is specified, matching lines are simply output one right after another. When nonzero context is specified, lines that are adjacent in the input form a group and are output one right after another, but disjoint groups of lines are separated by a ‘--’ without any prefix and on a line of its own. Each group may contain several matching lines when they are close enough to each other that two otherwise adjacent but divided groups connect and can just merge into a single contiguous one.
\ to quote a wildcard or backslash character literally.
mmap system call to read input,
instead of the default read system call.
In some situations, ‘--mmap’ yields better performance.
However, ‘--mmap’ can cause undefined behavior (including core dumps)
if an input file shrinks while grep is operating,
or if an I/O error occurs.
CR characters from the original file contents
(to make regular expressions with ^ and $ work correctly).
Specifying ‘-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.
NUL character) instead of a newline.
Like the ‘-Z’ or ‘--null’ option,
this option can be used with commands like
‘sort -z’ to process arbitrary file names.
The behavior of grep is affected by the following environment variables.
The locale for category LC_foo
is specified by examining the three environment variables
LC_ALL, LC_foo, and LANG,
in that order.
The first of these variables that is set specifies the locale.
For example, if LC_ALL is not set,
but LC_MESSAGES is set to ‘pt_BR’,
then the Brazilian Portuguese locale is used
for the 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 grep was not compiled
with national language support (nls).
GREP_OPTIONS is
‘--binary-files=without-match --directories=skip’, grep
behaves as if the two options ‘--binary-files=without-match’ and
‘--directories=skip’ had been specified before
any explicit options.
Option specifications are separated by
whitespace.
A backslash escapes the next character, so it can be used to
specify an option containing whitespace or a backslash.
GREP_COLORS, but still supported.
The ‘mt’, ‘ms’, and ‘mc’ capabilities of 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 ‘-v’ command-line option is omitted,
or a context line when ‘-v’ is specified).
The default is ‘01;31’,
which means a bold red foreground text on the terminal's default background.
sl=cx=rvmt=01;31ms=01;31mc=01;31fn=35ln=32bn=32se=36neback_color_erase
(bce) boolean terminfo capability does not apply,
when the chosen highlight colors do not affect the background,
or when EL is too slow or causes too much flicker.
The default is false (i.e., the capability is omitted).
Note that boolean capabilities have no ‘=’... part. They are omitted (i.e., false) by default and become true when specified.
See the Select Graphic Rendition (SGR) section
in the documentation of your text terminal
for permitted values and their meaning as character attributes.
These substring values are integers in decimal representation
and can be concatenated with semicolons.
grep takes care of assembling the result
into a complete SGR sequence (‘\33[’...‘m’).
Common values to concatenate include
‘1’ for bold,
‘4’ for underline,
‘5’ for blink,
‘7’ for inverse,
‘39’ for default foreground color,
‘30’ to ‘37’ for foreground colors,
‘90’ to ‘97’ for 16-color mode foreground colors,
‘38;5;0’ to ‘38;5;255’
for 88-color and 256-color modes foreground colors,
‘49’ for default background color,
‘40’ to ‘47’ for background colors,
‘100’ to ‘107’ for 16-color mode background colors,
and ‘48;5;0’ to ‘48;5;255’
for 88-color and 256-color modes background colors.
LC_COLLATE category,
which determines the collating sequence
used to interpret range expressions like ‘[a-z]’.
LC_CTYPE category,
which determines the type of characters,
e.g., which characters are whitespace.
LC_MESSAGES category,
which determines the language that grep uses for messages.
The default ‘C’ locale uses American English messages.
POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
described below.
POSIXLY_CORRECT is not set.
Normally, the exit status is 0 if selected lines are found and 1 otherwise. But the exit status is 2 if an error occurred, unless the -q or --quiet or --silent option is used and a selected line is found. Note, however, that posix only mandates, for programs such as grep, cmp, and diff, that the exit status in case of error be greater than 1; it is therefore advisable, for the sake of portability, to use logic that tests for this general condition instead of strict equality with 2.
grep searches the named input files (or standard input if no files are named, or the file name - is given) for lines containing a match to the given pattern. By default, grep prints the matching lines. There are four major variants of grep, controlled by the following options.
In addition, two variant programs egrep and fgrep are available. egrep is the same as ‘grep -E’. fgrep is the same as ‘grep -F’. Direct invocation as either egrep or fgrep is deprecated, but is provided to allow historical applications that rely on them to run unmodified.
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. grep understands two different versions of regular expression syntax: “basic”(BRE) and “extended”(ERE). In gnu grep, there is no difference in available functionality using either syntax. 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.
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.
A regular expression may be followed by one of several repetition operators:
Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions.
Two regular expressions may be joined by the infix operator ‘|’; the resulting regular expression matches any string matching either alternalte expression.
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.
A bracket expression is a list of characters enclosed by ‘[’ and ‘]’. It matches any single character in that list; if the first character of the list is the caret ‘^’, then it matches any character not in the list. For example, the regular expression ‘[0123456789]’ matches any single digit.
Within a bracket expression, a 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, ‘[a-d]’ is equivalent to ‘[abcd]’. Many locales sort characters in dictionary order, and in these locales ‘[a-d]’ is typically not equivalent to ‘[abcd]’; it might be equivalent to ‘[aBbCcDd]’, for example. To obtain the traditional interpretation of bracket expressions, you can use the ‘C’ locale by setting the LC_ALL environment variable to the value ‘C’.
Finally, certain named classes of characters are predefined within
bracket expressions, as follows.
Their interpretation depends on the LC_CTYPE locale;
the interpretation below is that of the ‘C’ locale,
which is the default if no LC_CTYPE locale is specified.
DEL).
In other character sets, these are
the equivalent characters, if any.
0 1 2 3 4 5 6 7 8 9.
a b c d e f g h i j k l m n o p q r s t u v w x y z.
! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z.
0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f.
Most meta-characters lose their special meaning inside bracket expressions.
The ‘\’ character, when followed by certain ordinary characters, takes a special meaning:
For example, ‘\brat\b’ matches the separate word ‘rat’, ‘\Brat\B’ matches ‘crate’ but not ‘furry rat’.
The caret ‘^’ and the dollar sign ‘$’ are meta-characters that respectively match the empty string at the beginning and end of a line.
The back-reference ‘\n’, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. For example, ‘(a)\1’ matches ‘aa’. When used with alternation, if the group does not participate in the match then the back-reference makes the whole match fail. For example, ‘a(.)|b\1’ will not match ‘ba’. When multiple regular expressions are given with ‘-e’ or from a file (‘-f file’), back-references are local to each expression.
In basic regular expressions the meta-characters ‘?’, ‘+’, ‘{’, ‘|’, ‘(’, and ‘)’ lose their special meaning; instead use the backslashed versions ‘\?’, ‘\+’, ‘\{’, ‘\|’, ‘\(’, and ‘\)’.
Traditional egrep did not support the ‘{’ meta-character, and some egrep implementations support ‘\{’ instead, so portable scripts should avoid ‘{’ in ‘grep -E’ patterns and should use ‘[{]’ to match a literal ‘{’.
gnu grep -E attempts to support traditional usage by assuming that ‘{’ is not special if it would be the start of an invalid interval specification. For example, the command ‘grep -E '{1'’ searches for the two-character string ‘{1’ instead of reporting a syntax error in the regular expression. posix.2 allows this behavior as an extension, but portable scripts should avoid it.
Here is an example command that invokes gnu grep:
grep -i 'hello.*world' menu.h main.c
This lists all lines in the files menu.h and main.c that contain the string ‘hello’ followed by the string ‘world’; this is because ‘.*’ matches zero or more characters within a line. See Regular Expressions. The ‘-i’ option causes grep to ignore case, causing it to match the line ‘Hello, world!’, which it would not otherwise match. See Invoking, for more details about how to invoke grep.
Here are some common questions and answers about grep usage.
grep -l 'main' *.c
lists the names of all C files in the current directory whose contents mention ‘main’.
grep -r 'hello' /home/gigi
searches for ‘hello’ in all files under the /home/gigi directory. For more control over which files are searched, use find, grep, and xargs. For example, the following command searches only C files:
find /home/gigi -name '*.c' -print0 | xargs -0r grep -H 'hello'
This differs from the command:
grep -rH 'hello' *.c
which merely looks for ‘hello’ in all files in the current directory whose names end in ‘.c’. Here the -r is probably unnecessary, as recursion occurs only in the unlikely event that one of ‘.c’ files is a directory. The ‘find ...’ command line above is more similar to the command:
grep -rH --include='*.c' 'hello' /home/gigi
grep -e '--cut here--' *
searches for all lines matching ‘--cut here--’. Without ‘-e’, grep would attempt to parse ‘--cut here--’ as a list of options.
grep -w 'hello' *
searches only for instances of ‘hello’ that are entire words; it does not match ‘Othello’. For more control, use ‘\<’ and ‘\>’ to match the start and end of words. For example:
grep 'hello\>' *
searches only for words ending in ‘hello’, so it matches the word ‘Othello’.
grep -C 2 'hello' *
prints two lines of context around each matching line.
Append /dev/null:
grep 'eli' /etc/passwd /dev/null
gets you:
/etc/passwd:eli:x:2098:1000:Eli Smith:/home/eli:/bin/bash
Alternatively, use ‘-H’, which is a gnu extension:
grep -H 'eli' /etc/passwd
ps -ef | grep '[c]ron'
If the pattern had been written without the square brackets, it would have matched not only the ps output line for cron, but also the ps output line for grep. Note that on some platforms, ps limits the output to the width of the screen; grep does not have any limit on the length of a line except the available memory.
If grep listed all matching “lines” from a binary file, it would probably generate output that is not useful, and it might even muck up your display. So gnu grep suppresses output from files that appear to be binary files. To force gnu grep to output lines even from files that appear to be binary, use the ‘-a’ or ‘--binary-files=text’ option. To eliminate the “Binary file matches” messages, use the ‘-I’ or ‘--binary-files=without-match’ option.
‘grep -lv’ lists the names of all files containing one or more lines that do not match. To list the names of all files that contain no matching lines, use the ‘-L’ or ‘--files-without-match’ option.
grep 'paul' /etc/motd | grep 'franc,ois'
finds all lines that contain both ‘paul’ and ‘franc,ois’.
Use the special file name ‘-’:
cat /etc/passwd | grep 'alain' - /etc/motd
It can be done by using back-references; for example, a palindrome of 4 characters can be written with a BRE:
grep -w -e '\(.\)\(.\).\2\1' file
It matches the word "radar" or "civic".
Guglielmo Bondioni proposed a single RE that finds all palindromes up to 19 characters long using 9 subexpressions and 9 back-references:
grep -E -e '^(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?).?\9\8\7\6\5\4\3\2\1$' file
Note this is done by using gnu ERE extensions; it might not be portable to other implementations of grep.
echo 'ba' | grep -E '(a)\1|b\1'
This gives no output, because the first alternate ‘(a)\1’ does not match, as there is no ‘aa’ in the input, so the ‘\1’ in the second alternate has nothing to refer back to, meaning it will never match anything. (The second alternate in this example can only match if the first alternate has matched – making the second one superfluous.)
The name grep comes from the way line editing was done on Unix. For example, ed uses the following syntax to print a list of matching lines on the screen:
global/regular expression/print
g/re/p
fgrep stands for Fixed grep; egrep stands for Extended grep.
Email bug reports to bug-grep@gnu.org, a mailing list whose web page is http://lists.gnu.org/mailman/listinfo/bug-grep. The Savannah bug tracker for grep is located at http://savannah.gnu.org/bugs/?group=grep.
Large repetition counts in the ‘{n,m}’ construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory.
Back-references are very slow, and may require exponential time.
GNU grep is licensed under the GNU GPL, which makes it free software.
Please note that “free” in “free software” refers to liberty, not price. As some GNU project advocates like to point out, think of “free speech” rather than “free beer”. The exact and legally binding distribution terms are spelled out below; in short, you have the right (freedom) to run and change grep and distribute it to other people, and even—if you want—charge money for doing either. The important restriction is that you have to grant your recipients the same rights and impose the same restrictions.
This method of licensing software is also known as open source because, among other things, it makes sure that all recipients will receive the source code along with the program, and be able to improve it. The GNU project prefers the term “free software” for reasons outlined at http://www.gnu.org/philosophy/free-software-for-freedom.html.
The exact license terms are defined by this paragraph and the GNU General Public License it refers to:
GNU grep is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.GNU grep is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
A copy of the GNU General Public License is included as part of this manual; if you did not receive it, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
In addition to this, this manual is free in the same sense:
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being “GNU General Public License” and “GNU Free Documentation License”, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
The full texts of the GNU General Public License and of the GNU Free Documentation License are available below.
Copyright © 1989, 1991 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software—to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.
We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.
Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.
Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.
The precise terms and conditions for copying, distribution and modification follow.
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.
You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.
These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.
Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.
In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.
The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.
If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.
If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.
It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.
Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.
If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.
one line to give the program's name and an idea of what it does.
Copyright (C) 19yy name of author
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
type `show w'. This is free software, and you are welcome
to redistribute it under certain conditions; type `show c'
for details.
The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than ‘show w’ and ‘show c’; they could even be mouse-clicks or menu items—whatever suits your program.
You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the program, if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright
interest in the program `Gnomovision'
(which makes passes at compilers) written
by James Hacker.
signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.
Copyright (C) 2000 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
The purpose of this License is to make a manual, textbook, or other written document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”.
A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.
A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.
The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.
A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not “Transparent” is called “Opaque”.
Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.
The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.
You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly display copies.
If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.
You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has less than five).
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section entitled “History”, and its title, and add to
it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section entitled “History” in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the “History” section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
K. In any section entitled “Acknowledgements” or “Dedications”,
preserve the section's title, and preserve in the section all the
substance and tone of each of the contributor acknowledgements
and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
M. Delete any section entitled “Endorsements”. Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section as “Endorsements”
or to conflict in title with any Invariant Section.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties–for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections entitled “History” in the various original documents, forming one section entitled “History”; likewise combine any sections entitled “Acknowledgements”, and any sections entitled “Dedications”. You must delete all sections entitled “Endorsements.”
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an “aggregate”, and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.
You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.
To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
Copyright (C) year your name.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with the Invariant Sections being list their titles, with the
Front-Cover Texts being list, and with the Back-Cover Texts being list.
A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have no Invariant Sections, write “with no Invariant Sections” instead of saying which ones are invariant. If you have no Front-Cover Texts, write “no Front-Cover Texts” instead of “Front-Cover Texts being list”; likewise for Back-Cover Texts.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.
This is a general index of all issues discussed in this manual, with the exception of all specific grep command-line options, environment variables, color capabilities, and regular expression constructs, which are covered in their own index.
This is an lexicographical list of all grep command-line options, environment variables, color capabilities, and regular expression constructs.
*: Fundamental Structure+: Fundamental Structure--after-context: Context Line Control--basic-regexp: grep Programs--before-context: Context Line Control--binary: Other Options--binary-files: File and Directory Selection--byte-offset: Output Line Prefix Control--color: General Output Control--colour: General Output Control--context: Context Line Control--count: General Output Control--devices: File and Directory Selection--directories: File and Directory Selection--exclude: File and Directory Selection--exclude-dir: File and Directory Selection--exclude-from: File and Directory Selection--extended-regexp: grep Programs--file: Matching Control--files-with-matches: General Output Control--files-without-match: General Output Control--fixed-strings: grep Programs--help: Generic Program Information--ignore-case: Matching Control--include: File and Directory Selection--initial-tab: Output Line Prefix Control--invert-match: Matching Control--label: Output Line Prefix Control--line-buffered: Other Options--line-number: Output Line Prefix Control--line-regexp: Matching Control--max-count: General Output Control--mmap: Other Options--no-filename: Output Line Prefix Control--no-messages: General Output Control--null: Output Line Prefix Control--null-data: Other Options--only-matching: General Output Control--perl-regexp: grep Programs--quiet: General Output Control--recursive: File and Directory Selection--regexp=pattern: Matching Control--silent: General Output Control--text: File and Directory Selection--unix-byte-offsets: Output Line Prefix Control--version: Generic Program Information--with-filename: Output Line Prefix Control--word-regexp: Matching Control-a: File and Directory Selection-A: Context Line Control-b: Output Line Prefix Control-B: Context Line Control-C: Context Line Control-c: General Output Control-D: File and Directory Selection-d: File and Directory Selection-e: Matching Control-E: grep Programs-f: Matching Control-F: grep Programs-G: grep Programs-h: Output Line Prefix Control-H: Output Line Prefix Control-i: Matching Control-L: General Output Control-l: General Output Control-m: General Output Control-n: Output Line Prefix Control-num: Context Line Control-o: General Output Control-P: grep Programs-q: General Output Control-r: File and Directory Selection-s: General Output Control-T: Output Line Prefix Control-U: Other Options-u: Output Line Prefix Control-V: Generic Program Information-v: Matching Control-w: Matching Control-x: Matching Control-y: Matching Control-Z: Output Line Prefix Control-z: Other Options.: Fundamental Structure?: Fundamental Structure_N_GNU_nonoption_argv_flags_ environment variable: Environment Variablesalnum character class: Character Classes and Bracket Expressionsalpha character class: Character Classes and Bracket Expressionsblank character class: Character Classes and Bracket Expressionsbn GREP_COLORS capability: Environment Variablescntrl character class: Character Classes and Bracket Expressionscx GREP_COLORS capability: Environment Variablesdigit character class: Character Classes and Bracket Expressionsfn GREP_COLORS capability: Environment Variablesgraph character class: Character Classes and Bracket ExpressionsGREP_COLOR environment variable: Environment VariablesGREP_COLORS environment variable: Environment VariablesGREP_OPTIONS environment variable: Environment VariablesLANG environment variable: Environment VariablesLC_ALL environment variable: Environment VariablesLC_COLLATE environment variable: Environment VariablesLC_CTYPE environment variable: Environment VariablesLC_MESSAGES environment variable: Environment Variablesln GREP_COLORS capability: Environment Variableslower character class: Character Classes and Bracket Expressionsmc GREP_COLORS capability: Environment Variablesms GREP_COLORS capability: Environment Variablesmt GREP_COLORS capability: Environment Variablesne GREP_COLORS capability: Environment VariablesPOSIXLY_CORRECT environment variable: Environment Variablesprint character class: Character Classes and Bracket Expressionspunct character class: Character Classes and Bracket Expressionsrv GREP_COLORS capability: Environment Variablessl GREP_COLORS capability: Environment Variablesspace character class: Character Classes and Bracket Expressionsupper character class: Character Classes and Bracket Expressionsxdigit character class: Character Classes and Bracket Expressions{,m}: Fundamental Structure{n,m}: Fundamental Structure{n,}: Fundamental Structure{n}: Fundamental Structure