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START-INFO-DIR-ENTRY
* grep: (grep).                   print lines matching a pattern.
END-INFO-DIR-ENTRY
   This file documents `grep', a pattern matching engine.

   Published by the Free Software Foundation, 59 Temple Place - Suite
330 Boston, MA 02111-1307, USA

   Copyright (C) 2000, 2001 Free Software Foundation, Inc.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   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" (*note Copying::).


File: grep,  Node: Top,  Next: Introduction,  Up: (dir)

Grep
****

   `grep' searches for lines matching a pattern.

   This document was produced for version 2.5 of GNU `grep'.

* Menu:

* Introduction::                Introduction.
* Invoking::                    Invoking `grep'; description of options.
* Diagnostics::                 Exit status returned by `grep'.
* Grep Programs::               `grep' programs.
* Regular Expressions::         Regular Expressions.
* Usage::                       Examples.
* Reporting Bugs::              Reporting Bugs.
* Copying::                     License terms.
* Concept Index::               A menu with all the topics in this manual.
* Index::                       A menu with all `grep' commands
                                 and command-line options.


File: grep,  Node: Introduction,  Next: Invoking,  Prev: Top,  Up: Top

1 Introduction
**************

   `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 does 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.


File: grep,  Node: Invoking,  Next: Diagnostics,  Prev: Introduction,  Up: Top

2 Invoking `grep'
*****************

   `grep' comes with a rich set of options from POSIX.2 and GNU
extensions.

`-c'
`--count'
     Suppress normal output; instead print a count of matching lines
     for each input file.  With the `-v', `--invert-match' option,
     count non-matching lines.

`-e PATTERN'
`--regexp=PATTERN'
     Use PATTERN as the pattern; useful to protect patterns beginning
     with a `-'.

`-f FILE'
`--file=FILE'
     Obtain patterns from FILE, one per line.  The empty file contains
     zero patterns, and therefore matches nothing.

`-i'
`--ignore-case'
     Ignore case distinctions in both the pattern and the input files.

`-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
     of every file will stop on the first match.

`-n'
`--line-number'
     Prefix each line of output with the line number within its input
     file.

`-o'
`--only-matching'
     Print only the part of matching lines that actually matches
     PATTERN.

`-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 `-s' or `--no-messages' option.

`-s'
`--no-messages'
     Suppress error messages about nonexistent or unreadable files.
     Portability note: unlike GNU `grep', traditional `grep' did not
     conform to POSIX.2, because traditional `grep' lacked a `-q'
     option and its `-s' option behaved like GNU `grep''s `-q' option.
     Shell scripts intended to be portable to traditional `grep' should
     avoid both `-q' and `-s' and should redirect output to `/dev/null'
     instead.

`-v'
`--invert-match'
     Invert the sense of matching, to select non-matching lines.

`-x'
`--line-regexp'
     Select only those matches that exactly match the whole line.

2.1 GNU Extensions
==================

`-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 of output context.

`--colour[=WHEN]'
`--color[=WHEN]'
     The matching string is surrounded by the marker specify in
     GREP_COLOR.  WHEN may be `never', `always', or `auto'.

`-NUM'
     Same as `--context=NUM' lines of leading and trailing context.
     However, grep will never print any given line more than once.

`-V'
`--version'
     Print the version number of `grep' to the standard output stream.
     This version number should be included in all bug reports.

`--help'
     Print a usage message briefly summarizing these command-line
     options and the bug-reporting address, then exit.

`--binary-files=TYPE'
     If the first few bytes of a file indicate that the file contains
     binary data, assume that the file is of type TYPE.  By default,
     TYPE is `binary', and `grep' normally outputs either a one-line
     message saying that a binary file matches, or no message if there
     is no match.  If TYPE is `without-match', `grep' assumes that a
     binary file does not match; this is equivalent to the `-I' option.
     If TYPE is `text', `grep' processes a binary file as if it were
     text; this is equivalent to the `-a' option.  _Warning:_
     `--binary-files=text' 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.

`-b'
`--byte-offset'
     Print the byte offset within the input file before each line of
     output.  When `grep' runs on MS-DOS or MS-Windows, the printed
     byte offsets depend on whether the `-u' (`--unix-byte-offsets')
     option is used; see below.

`-D ACTION'
`--devices=ACTION'
     If an input file is a device, FIFO or socket, use ACTION to
     process it.  By default, ACTION is `read', which means that
     devices are read just as if they were ordinary files.  If ACTION
     is `skip', devices, FIFOs and sockets are silently skipped.

`-d ACTION'
`--directories=ACTION'
     If an input file is a directory, use ACTION to process it.  By
     default, ACTION is `read', which means that directories are read
     just as if they were ordinary files (some operating systems and
     filesystems disallow this, and will cause `grep' to print error
     messages for every directory or silently skip them). If ACTION is
     `skip', directories are silently skipped.  If ACTION is `recurse',
     `grep' reads all files under each directory, recursively; this is
     equivalent to the `-r' option.

`-H'
`--with-filename'
     Print the filename for each match.

`-h'
`--no-filename'
     Suppress the prefixing of filenames on output when multiple files
     are searched.

`--line-buffered'
     Set the line buffering policy, this can be a performance penality.

`--label=LABEL'
     Displays input actually coming from standard input as input coming
     from file LABEL. This is especially useful for tools like zgrep,
     e.g.  `gzip -cd foo.gz |grep --label=foo something'

`-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 of every file will stop on the first match.

`-a'
`--text'
     Process a binary file as if it were text; this is equivalent to the
     `--binary-files=text' option.

`-I'
     Process a binary file as if it did not contain matching data; this
     is equivalent to the `--binary-files=without-match' option.

`-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.

`-r'
`-R'
`--recursive'
     For each directory mentioned in the command line, read and process
     all files in that directory, recursively.  This is the same as the
     `--directories=recurse' option.

`--include=FILE_PATTERN'
     When processing directories recursively, only files matching
     FILE_PATTERN will be search.

`--exclude=FILE_PATTERN'
     When processing directories recursively, skip files matching
     FILE_PATTERN.

`-m NUM'
`--max-count=NUM'
     Stop reading a file after NUM matching lines.  If the input is
     standard input from a regular file, and NUM matching lines are
     output, `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.  For example, the following shell script makes
     use of it:

          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.

`-y'
     Obsolete synonym for `-i'.

`-U'
`--binary'
     Treat the file(s) as binary.  By default, under MS-DOS and
     MS-Windows, `grep' guesses the file type by looking at the
     contents of the first 32kB read from the file.  If `grep' decides
     the file is a text file, it strips the `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.

`-u'
`--unix-byte-offsets'
     Report Unix-style byte offsets.  This switch causes `grep' to
     report byte offsets as if the file were Unix style text file,
     i.e., the byte offsets ignore the `CR' characters which were
     stripped.  This will produce results identical to running `grep' on
     a Unix machine.  This option has no effect unless `-b' option is
     also used; it has no effect on platforms other than MS-DOS and
     MS-Windows.

`--mmap'
     If possible, use the `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.

`-Z'
`--null'
     Output a zero byte (the ASCII `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.

`-z'
`--null-data'
     Treat the input as a set of lines, each terminated by a zero byte
     (the ASCII `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.

   Several additional options control which variant of the `grep'
matching engine is used.  *Note Grep Programs::.

2.2 Environment Variables
=========================

   Grep's behavior is affected by the following environment variables.

   A locale `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
Brazilian Portuguese is used for the `LC_MESSAGES' locale.  The C
locale is used if none of these environment variables are set, or if
the locale catalog is not installed, or if `grep' was not compiled with
national language support (NLS).

`GREP_OPTIONS'
     This variable specifies default options to be placed in front of
     any explicit options.  For example, if `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_COLOR'
     This variable specifies the surrounding markers use to highlight
     the matching text.  The default is control ascii red.

`LC_ALL'
`LC_COLLATE'
`LANG'
     These variables specify the `LC_COLLATE' locale, which determines
     the collating sequence used to interpret range expressions like
     `[a-z]'.

`LC_ALL'
`LC_CTYPE'
`LANG'
     These variables specify the `LC_CTYPE' locale, which determines the
     type of characters, e.g., which characters are whitespace.

`LC_ALL'
`LC_MESSAGES'
`LANG'
     These variables specify the `LC_MESSAGES' locale, which determines
     the language that `grep' uses for messages.  The default C locale
     uses American English messages.

`POSIXLY_CORRECT'
     If set, `grep' behaves as POSIX.2 requires; otherwise, `grep'
     behaves more like other GNU programs.  POSIX.2 requires that
     options that follow file names must be treated as file names; by
     default, such options are permuted to the front of the operand
     list and are treated as options.  Also, POSIX.2 requires that
     unrecognized options be diagnosed as "illegal", but since they are
     not really against the law the default is to diagnose them as
     "invalid".  `POSIXLY_CORRECT' also disables
     `_N_GNU_nonoption_argv_flags_', described below.

`_N_GNU_nonoption_argv_flags_'
     (Here `N' is `grep''s numeric process ID.)  If the Ith character
     of this environment variable's value is `1', do not consider the
     Ith operand of `grep' to be an option, even if it appears to be
     one.  A shell can put this variable in the environment for each
     command it runs, specifying which operands are the results of file
     name wildcard expansion and therefore should not be treated as
     options.  This behavior is available only with the GNU C library,
     and only when `POSIXLY_CORRECT' is not set.


File: grep,  Node: Diagnostics,  Next: Grep Programs,  Prev: Invoking,  Up: Top

3 Diagnostics
*************

   Normally, 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.


File: grep,  Node: Grep Programs,  Next: Regular Expressions,  Prev: Diagnostics,  Up: Top

4 `grep' programs
*****************

   `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.

`-G'
`--basic-regexp'
     Interpret the pattern as a basic regular expression.  This is the
     default.

`-E'
`--extended-regexp'
     Interpret the pattern as an extended regular expression.

`-F'
`--fixed-strings'
     Interpret the pattern as a list of fixed strings, separated by
     newlines, any of which is to be matched.

`-P'
`--perl-regexp'
     Interpret the pattern as a Perl regular expression.

   In addition, two variant programs EGREP and FGREP are available.
EGREP is the same as `grep -E'.  FGREP is the same as `grep -F'.


File: grep,  Node: Regular Expressions,  Next: Usage,  Prev: Grep Programs,  Up: Top

5 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.
`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
metacharacter with special meaning may be quoted by preceding it with a
backslash.

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

`.'
     The period `.' matches any single character.

`?'
     The preceding item is optional and will be matched at most once.

`*'
     The preceding item will be matched zero or more times.

`+'
     The preceding item will be matched one or more times.

`{N}'
     The preceding item is matched exactly N times.

`{N,}'
     The preceding item is matched n or more times.

`{N,M}'
     The preceding item is matched at least N times, but not more than
     M times.

   Two regular expressions may be concatenated; the resulting regular
expression matches any string formed by concatenating two substrings
that respectively match the concatenated subexpressions.

   Two regular expressions may be joined by the infix operator `|'; the
resulting regular expression matches any string matching either
subexpression.

   Repetition takes precedence over concatenation, which in turn takes
precedence over alternation.  A whole subexpression may be enclosed in
parentheses to override these precedence rules.

5.1 Character Class
===================

   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.

`[:alnum:]'
     Alphanumeric characters: `[:alpha:]' and `[:digit:]'.

`[:alpha:]'
     Alphabetic characters: `[:lower:]' and `[:upper:]'.

`[:blank:]'
     Blank characters: space and tab.

`[:cntrl:]'
     Control characters.  In ASCII, these characters have octal codes
     000 through 037, and 177 (`DEL').  In other character sets, these
     are the equivalent characters, if any.

`[:digit:]'
     Digits: `0 1 2 3 4 5 6 7 8 9'.

`[:graph:]'
     Graphical characters: `[:alnum:]' and `[:punct:]'.

`[:lower:]'
     Lower-case letters: `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'.

`[:print:]'
     Printable characters: `[:alnum:]', `[:punct:]', and space.

`[:punct:]'
     Punctuation characters: `! " # $ % & ' ( ) * + , - . / : ; < = > ?
     @ [ \ ] ^ _ ` { | } ~'.

`[:space:]'
     Space characters: tab, newline, vertical tab, form feed, carriage
     return, and space.

`[:upper:]'
     Upper-case letters: `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'.

`[:xdigit:]'
     Hexadecimal digits: `0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f'.

   For example, `[[:alnum:]]' means `[0-9A-Za-z]', except the latter
depends upon the C locale and the ASCII character encoding, whereas the
former is independent of locale and character set.  (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 list.)

   Most metacharacters lose their special meaning inside lists.

`]'
     ends the list if it's not the first list item.  So, if you want to
     make the `]' character a list item, you must put it first.

`[.'
     represents the open collating symbol.

`.]'
     represents the close collating symbol.

`[='
     represents the open equivalence class.

`=]'
     represents the close equivalence class.

`[:'
     represents the open character class followed by a valid character
     class name.

`:]'
     represents the close character class followed by a valid character
     class name.

`-'
     represents the range if it's not first or last in a list or the
     ending point of a range.

`^'
     represents the characters not in the list.  If you want to make
     the `^' character a list item, place it anywhere but first.

5.2 Backslash Character
=======================

   The `\' when followed by certain ordinary characters take a special
meaning :

``\b''
     Match the empty string at the edge of a word.

``\B''
     Match the empty string provided it's not at the edge of a word.

``\<''
     Match the empty string at the beginning of word.

``\>''
     Match the empty string at the end of word.

``\w''
     Match word constituent, it is a synonym for `[[:alnum:]]'.

``\W''
     Match non word constituent, it is a synonym for `[^[:alnum:]]'.

   For example , `\brat\b' matches the separate word `rat', `c\Brat\Be'
matches `crate', but `dirty \Brat' doesn't match `dirty rat'.

5.3 Anchoring
=============

   The caret `^' and the dollar sign `$' are metacharacters that
respectively match the empty string at the beginning and end of a line.

5.4 Back-reference
==================

   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 use
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', the back-referecences are local to each
expression.

5.5 Basic vs Extended
=====================

   In basic regular expressions the metacharacters `?', `+', `{', `|',
`(', and `)' lose their special meaning; instead use the backslashed
versions `\?', `\+', `\{', `\|', `\(', and `\)'.

   Traditional `egrep' did not support the `{' metacharacter, and some
`egrep' implementations support `\{' instead, so portable scripts
should avoid `{' in `egrep' patterns and should use `[{]' to match a
literal `{'.

   GNU `egrep' 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 shell command `egrep '{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.


File: grep,  Node: Usage,  Next: Reporting Bugs,  Prev: Regular Expressions,  Up: Top

6 Usage
*******

   Here is an example shell 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.  *Note Regular
Expressions::.  The `-i' option causes `grep' to ignore case, causing
it to match the line `Hello, world!', which it would not otherwise
match.  *Note Invoking::, for more details about how to invoke `grep'.

   Here are some common questions and answers about `grep' usage.

  1. How can I list just the names of matching files?

          grep -l 'main' *.c

     lists the names of all C files in the current directory whose
     contents mention `main'.

  2. How do I search directories recursively?

          grep -r 'hello' /home/gigi

     searches for `hello' in all files under the directory
     `/home/gigi'.  For more control of which files are searched, use
     `find', `grep' and `xargs'.  For example, the following command
     searches only C files:

          find /home/gigi -name '*.c' -print | xargs grep 'hello' /dev/null

     This differs from the command:

          grep -r '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.

  3. What if a pattern has a leading `-'?

          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.

  4. Suppose I want to search for a whole word, not a part of a word?

          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'.

  5. How do I output context around the matching lines?

          grep -C 2 'hello' *

     prints two lines of context around each matching line.

  6. How do I force grep to print the name of the file?

     Append `/dev/null':

          grep 'eli' /etc/passwd /dev/null

     gets you:

          /etc/passwd:eli:DNGUTF58.IMe.:98:11:Eli Smith:/home/do/eli:/bin/bash

  7. Why do people use strange regular expressions on `ps' output?

          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 some platforms
     `ps' limit the ouput to the width of the screen, grep does not
     have any limit on the length of a line except the available memory.

  8. Why does `grep' report "Binary file matches"?

     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.

  9. Why doesn't `grep -lv' print nonmatching file names?

     `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.

 10. I can do OR with `|', but what about AND?

          grep 'paul' /etc/motd | grep 'franc,ois'

     finds all lines that contain both `paul' and `franc,ois'.

 11. How can I search in both standard input and in files?

     Use the special file name `-':

          cat /etc/passwd | grep 'alain' - /etc/motd

 12. How to express palindromes in a regular expression?

     It can be done by using the back referecences, for example a
     palindrome of 4 chararcters can be written in BRE.

          grep -w -e '\(.\)\(.\).\2\1' file

     It matches the word "radar" or "civic".

     Guglielmo Bondioni proposed a single RE that finds all the
     palindromes up to 19 characters long.

          egrep -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 on other greps.

 13. Why are my expressions whith the vertical bar fail?

          /bin/echo "ba" | egrep '(a)\1|(b)\1'

     The first alternate branch fails then the first group was not in
     the match this will make the second alternate branch fails.  For
     example, "aaba" will match, the first group participate in the
     match and can be reuse in the second branch.

 14. What do `grep, fgrep, egrep' stand for ?

     grep comes from the way line editing was done on Unix.  For
     example, `ed' uses this syntax to print a list of matching lines
     on the screen.

          global/regular expression/print
          g/re/p

     `fgrep' stands for Fixed `grep', `egrep' Extended `grep'.



File: grep,  Node: Reporting Bugs,  Next: Copying,  Prev: Usage,  Up: Top

7 Reporting bugs
****************

   Email bug reports to <bug-gnu-utils@gnu.org>.  Be sure to include
the word "grep" somewhere in the "Subject:" field.

   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.


File: grep,  Node: Copying,  Next: GNU General Public License,  Prev: Reporting Bugs,  Up: Top

8 Copying
*********

   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.

* Menu:

* GNU General Public License:: GNU GPL
* GNU Free Documentation License:: GNU FDL


File: grep,  Node: GNU General Public License,  Next: GNU Free Documentation License,  Prev: Copying,  Up: Copying

8.1 GNU General Public License
==============================

                         Version 2, June 1991

     Copyright (C) 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.

Preamble
========

   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.

    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
  1. This License applies to any program or other work which contains a
     notice placed by the copyright holder saying it may be distributed
     under the terms of this General Public License.  The "Program",
     below, refers to any such program or work, and a "work based on
     the Program" means either the Program or any derivative work under
     copyright law: that is to say, a work containing the Program or a
     portion of it, either verbatim or with modifications and/or
     translated into another language.  (Hereinafter, translation is
     included without limitation in the term "modification".)  Each
     licensee is addressed as "you".

     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.

  2. You may copy and distribute verbatim copies of the Program's
     source code as you receive it, in any medium, provided that you
     conspicuously and appropriately publish on each copy an appropriate
     copyright notice and disclaimer of warranty; keep intact all the
     notices that refer to this License and to the absence of any
     warranty; and give any other recipients of the Program a copy of
     this License along with the Program.

     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.

  3. You may modify your copy or copies of the Program or any portion
     of it, thus forming a work based on the Program, and copy and
     distribute such modifications or work under the terms of Section 1
     above, provided that you also meet all of these conditions:

       a. You must cause the modified files to carry prominent notices
          stating that you changed the files and the date of any change.

       b. You must cause any work that you distribute or publish, that
          in whole or in part contains or is derived from the Program
          or any part thereof, to be licensed as a whole at no charge
          to all third parties under the terms of this License.

       c. If the modified program normally reads commands interactively
          when run, you must cause it, when started running for such
          interactive use in the most ordinary way, to print or display
          an announcement including an appropriate copyright notice and
          a notice that there is no warranty (or else, saying that you
          provide a warranty) and that users may redistribute the
          program under these conditions, and telling the user how to
          view a copy of this License.  (Exception: if the Program
          itself is interactive but does not normally print such an
          announcement, your work based on the Program is not required
          to print an announcement.)

     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.

  4. You may copy and distribute the Program (or a work based on it,
     under Section 2) in object code or executable form under the terms
     of Sections 1 and 2 above provided that you also do one of the
     following:

       a. Accompany it with the complete corresponding machine-readable
          source code, which must be distributed under the terms of
          Sections 1 and 2 above on a medium customarily used for
          software interchange; or,

       b. Accompany it with a written offer, valid for at least three
          years, to give any third party, for a charge no more than your
          cost of physically performing source distribution, a complete
          machine-readable copy of the corresponding source code, to be
          distributed under the terms of Sections 1 and 2 above on a
          medium customarily used for software interchange; or,

       c. Accompany it with the information you received as to the offer
          to distribute corresponding source code.  (This alternative is
          allowed only for noncommercial distribution and only if you
          received the program in object code or executable form with
          such an offer, in accord with Subsection b above.)

     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.

  5. You may not copy, modify, sublicense, or distribute the Program
     except as expressly provided under this License.  Any attempt
     otherwise to copy, modify, sublicense or distribute the Program 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.

  6. You are not required to accept this License, since you have not
     signed it.  However, nothing else grants you permission to modify
     or distribute the Program or its derivative works.  These actions
     are prohibited by law if you do not accept this License.
     Therefore, by modifying or distributing the Program (or any work
     based on the Program), you indicate your acceptance of this
     License to do so, and all its terms and conditions for copying,
     distributing or modifying the Program or works based on it.

  7. Each time you redistribute the Program (or any work based on the
     Program), the recipient automatically receives a license from the
     original licensor to copy, distribute or modify the Program
     subject to these terms and conditions.  You may not impose any
     further restrictions on the recipients' exercise of the rights
     granted herein.  You are not responsible for enforcing compliance
     by third parties to this License.

  8. If, as a consequence of a court judgment or allegation of patent
     infringement or for any other reason (not limited to patent
     issues), conditions are imposed on you (whether by court order,
     agreement or otherwise) that contradict the conditions of this
     License, they do not excuse you from the conditions of this
     License.  If you cannot distribute so as to satisfy simultaneously
     your obligations under this License and any other pertinent
     obligations, then as a consequence you may not distribute the
     Program at all.  For example, if a patent license would not permit
     royalty-free redistribution of the Program by all those who
     receive copies directly or indirectly through you, then the only
     way you could satisfy both it and this License would be to refrain
     entirely from distribution of the Program.

     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.

  9. If the distribution and/or use of the Program is restricted in
     certain countries either by patents or by copyrighted interfaces,
     the original copyright holder who places the Program under this
     License may add an explicit geographical distribution limitation
     excluding those countries, so that distribution is permitted only
     in or among countries not thus excluded.  In such case, this
     License incorporates the limitation as if written in the body of
     this License.

 10. The Free Software Foundation may publish revised and/or new
     versions of the General Public 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.

     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.

 11. If you wish to incorporate parts of the Program into other free
     programs whose distribution conditions are different, write to the
     author to ask for permission.  For software which is copyrighted
     by the Free Software Foundation, write to the Free Software
     Foundation; we sometimes make exceptions for this.  Our decision
     will be guided by the two goals of preserving the free status of
     all derivatives of our free software and of promoting the sharing
     and reuse of software generally.

                                NO WARRANTY

 12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
     WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE
     LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
     HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT
     WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT
     NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
     FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS TO THE
     QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
     PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY
     SERVICING, REPAIR OR CORRECTION.

 13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY
     MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE
     LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,
     INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR
     INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
     DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU
     OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY
     OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
     ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

                      END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs
=============================================

   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.


File: grep,  Node: GNU Free Documentation License,  Next: Concept Index,  Prev: GNU General Public License,  Up: Copying

8.2 GNU Free Documentation License
==================================

                        Version 1.1, March 2000

     Copyright (C) 2000  Free Software Foundation, Inc.
     59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.


  0. PREAMBLE

     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.


  1. APPLICABILITY AND DEFINITIONS

     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.

  2. VERBATIM COPYING

     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.

  3. COPYING IN QUANTITY

     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.

  4. MODIFICATIONS

     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
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     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
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     that was published at    least four years before the Document
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     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
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     You may add a section entitled "Endorsements", provided it contains
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     You may add a passage of up to five words as a Front-Cover Text,
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     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
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  5. COMBINING DOCUMENTS

     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
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     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
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     In the combination, you must combine any sections entitled
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     entitled "History"; likewise combine any sections entitled
     "Acknowledgements", and any sections entitled "Dedications".  You
     must delete all sections entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     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.

  7. AGGREGATION WITH INDEPENDENT WORKS

     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.

  8. TRANSLATION

     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.

  9. TERMINATION

     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.

 10. FUTURE REVISIONS OF THIS LICENSE

     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.


ADDENDUM: How to use this License for your documents
====================================================

   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.


File: grep,  Node: Concept Index,  Next: Index,  Prev: GNU Free Documentation License,  Up: Top

Concept Index
*************

   This is a general index of all issues discussed in this manual, with
the exception of the `grep' commands and command-line options.

* Menu:

* after context:                         Invoking.
* alphabetic characters:                 Regular Expressions.
* alphanumeric characters:               Regular Expressions.
* anchoring:                             Regular Expressions.
* asterisk:                              Regular Expressions.
* back-reference:                        Regular Expressions.
* backslash:                             Regular Expressions.
* basic regular expressions:             Regular Expressions.
* before context:                        Invoking.
* binary files:                          Invoking.
* binary files, DOS/Windows:             Invoking.
* blank characters:                      Regular Expressions.
* braces, one argument:                  Regular Expressions.
* braces, second argument omitted:       Regular Expressions.
* braces, two arguments:                 Regular Expressions.
* bracket expression:                    Regular Expressions.
* Bugs, reporting:                       Reporting Bugs.
* byte offset:                           Invoking.
* byte offsets, on DOS/Windows:          Invoking.
* case insensitive search:               Invoking.
* case insensitive search, obsolete option: Invoking.
* changing name of standard input:       Invoking.
* character class:                       Regular Expressions.
* character classes:                     Regular Expressions.
* character type:                        Invoking.
* classes of characters:                 Regular Expressions.
* context:                               Invoking.
* context lines, after match:            Invoking.
* context lines, before match:           Invoking.
* control characters:                    Regular Expressions.
* Copying:                               Copying.
* counting lines:                        Invoking.
* default options environment variable:  Invoking.
* device search:                         Invoking.
* digit characters:                      Regular Expressions.
* directory search:                      Invoking.
* DOS byte offsets:                      Invoking.
* DOS/Windows binary files:              Invoking.
* dot:                                   Regular Expressions.
* environment variables:                 Invoking.
* exclude files:                         Invoking.
* FAQ about grep usage:                  Usage.
* FDL, GNU Free Documentation License:   GNU Free Documentation License.
* files which don't match:               Invoking.
* GPL, GNU General Public License:       GNU General Public License.
* graphic characters:                    Regular Expressions.
* hexadecimal digits:                    Regular Expressions.
* highlight markers:                     Invoking.
* highlight, color, colour:              Invoking.
* include files:                         Invoking.
* interval specifications:               Regular Expressions.
* invert matching:                       Invoking.
* language of messages:                  Invoking.
* line buffering:                        Invoking.
* line numbering:                        Invoking.
* lower-case letters:                    Regular Expressions.
* match sub-expression at most once:     Regular Expressions.
* match sub-expression n or more times:  Regular Expressions.
* match sub-expression n times:          Regular Expressions.
* match sub-expression zero or more times: Regular Expressions.
* match the whole line:                  Invoking.
* matching basic regular expressions:    Grep Programs.
* matching extended regular expressions: Grep Programs.
* matching fixed strings:                Grep Programs.
* matching Perl regular expressions:     Grep Programs.
* matching whole words:                  Invoking.
* max-count:                             Invoking.
* memory mapped input:                   Invoking.
* message language:                      Invoking.
* names of matching files:               Invoking.
* national language support:             Invoking.
* NLS:                                   Invoking.
* no filename prefix:                    Invoking.
* no warranty:                           GNU General Public License.
* numeric characters:                    Regular Expressions.
* only matching:                         Invoking.
* palindromes:                           Usage.
* pattern from file:                     Invoking.
* pattern list:                          Invoking.
* period:                                Regular Expressions.
* plus sign:                             Regular Expressions.
* print non-matching lines:              Invoking.
* printable characters:                  Regular Expressions.
* punctuation characters:                Regular Expressions.
* question mark:                         Regular Expressions.
* quiet, silent:                         Invoking.
* range expression:                      Regular Expressions.
* recursive search:                      Invoking.
* regular expressions:                   Regular Expressions.
* searching directory trees:             Invoking.
* Searching for a pattern.:              Introduction.
* space characters:                      Regular Expressions.
* suppress binary data:                  Invoking.
* suppress error messages:               Invoking.
* translation of message language:       Invoking.
* upper-case letters:                    Regular Expressions.
* Usage summary, printing:               Invoking.
* Usage, examples:                       Usage.
* Using grep, Q&A:                       Usage.
* Version, printing:                     Invoking.
* whitespace characters:                 Regular Expressions.
* with filename prefix:                  Invoking.
* xdigit class:                          Regular Expressions.
* zero-terminated file names:            Invoking.
* zero-terminated lines:                 Invoking.


File: grep,  Node: Index,  Prev: Concept Index,  Up: Top

Index
*****

   This is an alphabetical list of all `grep' commands, command-line
options, and environment variables.

* Menu:

* *:                                     Regular Expressions.
* +:                                     Regular Expressions.
* --after-context:                       Invoking.
* --basic-regexp:                        Grep Programs.
* --before-context:                      Invoking.
* --binary:                              Invoking.
* --binary-files:                        Invoking.
* --byte-offset:                         Invoking.
* --colour:                              Invoking.
* --context:                             Invoking.
* --count:                               Invoking.
* --devices:                             Invoking.
* --directories:                         Invoking.
* --exclude:                             Invoking.
* --extended-regexp:                     Grep Programs.
* --file:                                Invoking.
* --files-with-matches:                  Invoking.
* --files-without-match:                 Invoking.
* --fixed-strings:                       Grep Programs.
* --help:                                Invoking.
* --ignore-case:                         Invoking.
* --include:                             Invoking.
* --invert-match:                        Invoking.
* --label:                               Invoking.
* --line-buffered:                       Invoking.
* --line-number:                         Invoking.
* --line-regexp:                         Invoking.
* --max-count:                           Invoking.
* --mmap:                                Invoking.
* --no-filename:                         Invoking.
* --no-messages:                         Invoking.
* --null:                                Invoking.
* --null-data:                           Invoking.
* --only-matching:                       Invoking.
* --perl-regexp:                         Grep Programs.
* --quiet:                               Invoking.
* --recursive:                           Invoking.
* --regexp=PATTERN:                      Invoking.
* --silent:                              Invoking.
* --text:                                Invoking.
* --unix-byte-offsets:                   Invoking.
* --version:                             Invoking.
* --With-filename:                       Invoking.
* --word-regexp:                         Invoking.
* -a:                                    Invoking.
* -A:                                    Invoking.
* -b:                                    Invoking.
* -B:                                    Invoking.
* -C:                                    Invoking.
* -c:                                    Invoking.
* -d:                                    Invoking.
* -D:                                    Invoking.
* -E:                                    Grep Programs.
* -e:                                    Invoking.
* -F:                                    Grep Programs.
* -f:                                    Invoking.
* -G:                                    Grep Programs.
* -h:                                    Invoking.
* -H:                                    Invoking.
* -i:                                    Invoking.
* -L:                                    Invoking.
* -l:                                    Invoking.
* -m:                                    Invoking.
* -n:                                    Invoking.
* -NUM:                                  Invoking.
* -o:                                    Invoking.
* -P:                                    Grep Programs.
* -q:                                    Invoking.
* -r:                                    Invoking.
* -s:                                    Invoking.
* -u:                                    Invoking.
* -U:                                    Invoking.
* -V:                                    Invoking.
* -v:                                    Invoking.
* -w:                                    Invoking.
* -x:                                    Invoking.
* -y:                                    Invoking.
* -z:                                    Invoking.
* -Z:                                    Invoking.
* .:                                     Regular Expressions.
* ?:                                     Regular Expressions.
* _N_GNU_nonoption_argv_flags_:          Invoking.
* alnum:                                 Regular Expressions.
* alpha:                                 Regular Expressions.
* blank:                                 Regular Expressions.
* cntrl:                                 Regular Expressions.
* digit:                                 Regular Expressions.
* graph:                                 Regular Expressions.
* GREP_COLOR:                            Invoking.
* GREP_OPTIONS:                          Invoking.
* LANG:                                  Invoking.
* LC_ALL:                                Invoking.
* LC_COLLATE:                            Invoking.
* LC_CTYPE:                              Invoking.
* LC_MESSAGES:                           Invoking.
* lower:                                 Regular Expressions.
* POSIXLY_CORRECT:                       Invoking.
* print:                                 Regular Expressions.
* punct:                                 Regular Expressions.
* space:                                 Regular Expressions.
* upper:                                 Regular Expressions.
* xdigit:                                Regular Expressions.
* {n,m}:                                 Regular Expressions.
* {n,}:                                  Regular Expressions.
* {n}:                                   Regular Expressions.



Tag Table:
Node: Top1068
Node: Introduction1880
Node: Invoking2606
Node: Diagnostics16010
Node: Grep Programs16334
Node: Regular Expressions17303
Node: Usage25179
Node: Reporting Bugs30609
Node: Copying31134
Node: GNU General Public License33777
Node: GNU Free Documentation License52979
Node: Concept Index72724
Node: Index78851

End Tag Table
