File: grep.info-t, Node: Top, Next: Introduction, Up: (dir)
grep
****
'grep' prints lines that contain a match for a pattern.
This manual is for version 3.1 of GNU Grep.
This manual is for 'grep', a pattern matching engine.
Copyright (C) 1999-2002, 2005, 2008-2017 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, 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".
* Menu:
* Introduction:: Introduction.
* Invoking:: Command-line options, environment, exit status.
* Regular Expressions:: Regular Expressions.
* Usage:: Examples.
* Performance:: Performance tuning.
* Reporting Bugs:: Reporting Bugs.
* Copying:: License terms for this manual.
* Index:: Combined index.
File: grep.info-t, Node: Introduction, Next: Invoking, Prev: Top, Up: Top
1 Introduction
**************
'grep' searches 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.
File: grep.info-t, Node: Invoking, Next: Regular Expressions, Prev: Introduction, Up: Top
2 Invoking 'grep'
*****************
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.
* Menu:
* Command-line Options:: Short and long names, grouped by category.
* Environment Variables:: POSIX, GNU generic, and GNU grep specific.
* Exit Status:: Exit status returned by 'grep'.
* grep Programs:: 'grep' programs.
File: grep.info-t, Node: Command-line Options, Next: Environment Variables, Up: Invoking
2.1 Command-line Options
========================
'grep' comes with a rich set of options: some from POSIX 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.
* Menu:
* Generic Program Information::
* Matching Control::
* General Output Control::
* Output Line Prefix Control::
* Context Line Control::
* File and Directory Selection::
* Other Options::
Several additional options control which variant of the 'grep'
matching engine is used. *Note grep Programs::.
File: grep.info-t, Node: Generic Program Information, Next: Matching Control, Up: Command-line Options
2.1.1 Generic Program Information
---------------------------------
'--help'
Print a usage message briefly summarizing the command-line options
and the bug-reporting address, then exit.
'-V'
'--version'
Print the version number of 'grep' to the standard output stream.
This version number should be included in all bug reports.
File: grep.info-t, Node: Matching Control, Next: General Output Control, Prev: Generic Program Information, Up: Command-line Options
2.1.2 Matching Control
----------------------
'-e PATTERN'
'--regexp=PATTERN'
Use PATTERN as the pattern. If this option is used multiple times
or is combined with the '-f' ('--file') option, search for all
patterns given. ('-e' is specified by POSIX.)
'-f FILE'
'--file=FILE'
Obtain patterns from FILE, one per line. If this option is used
multiple times or is combined with the '-e' ('--regexp') option,
search for all patterns given. The empty file contains zero
patterns, and therefore matches nothing. ('-f' is specified by
POSIX.)
'-i'
'-y'
'--ignore-case'
Ignore case distinctions, so that characters that differ only in
case match each other. Although this is straightforward when
letters differ in case only via lowercase-uppercase pairs, the
behavior is unspecified in other situations. For example,
uppercase "S" has an unusual lowercase counterpart "??" (Unicode
character U+017F, LATIN SMALL LETTER LONG S) in many locales, and
it is unspecified whether this unusual character matches "S" or "s"
even though uppercasing it yields "S". Another example: the
lowercase German letter "ss" (U+00DF, LATIN SMALL LETTER SHARP S) is
normally capitalized as the two-character string "SS" but it does
not match "SS", and it might not match the uppercase letter "???"
(U+1E9E, LATIN CAPITAL LETTER SHARP S) even though lowercasing the
latter yields the former.
'-y' is an obsolete synonym that is provided for compatibility.
('-i' is specified by POSIX.)
'-v'
'--invert-match'
Invert the sense of matching, to select non-matching lines. ('-v'
is specified by POSIX.)
'-w'
'--word-regexp'
Select only those lines containing matches that form whole words.
The test is that the matching substring must either be at the
beginning of the line, or preceded by a non-word constituent
character. Similarly, it must be either at the end of the line or
followed by a non-word constituent character. Word-constituent
characters are letters, digits, and the underscore. This option
has no effect if '-x' is also specified.
'-x'
'--line-regexp'
Select only those matches that exactly match the whole line. For a
regular expression pattern, this is like parenthesizing the pattern
and then surrounding it with '^' and '$'. ('-x' is specified by
POSIX.)
File: grep.info-t, Node: General Output Control, Next: Output Line Prefix Control, Prev: Matching Control, Up: Command-line Options
2.1.3 General Output Control
----------------------------
'-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. ('-c' is specified by POSIX.)
'--color[=WHEN]'
'--colour[=WHEN]'
Surround the matched (non-empty) strings, matching lines, context
lines, file names, line numbers, byte offsets, and separators (for
fields and groups of context lines) with escape sequences to
display them in color on the terminal. The colors are defined by
the environment variable 'GREP_COLORS' and default to
'ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36' for bold red
matched text, magenta file names, green line numbers, green byte
offsets, cyan separators, and default terminal colors otherwise.
The deprecated environment variable 'GREP_COLOR' is still
supported, but its setting does not have priority; it defaults to
'01;31' (bold red) which only covers the color for matched text.
WHEN is 'never', 'always', or 'auto'.
'-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 each file stops on the first match.
'-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 each file stops on the first match. ('-l' is specified by
POSIX.)
'-m NUM'
'--max-count=NUM'
Stop after the first NUM selected lines. If the input is standard
input from a regular file, and NUM selected lines are output,
'grep' ensures that the standard input is positioned just after the
last selected 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 selected lines, it outputs any trailing
context lines. 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.
'-o'
'--only-matching'
Print only the matched (non-empty) parts of matching lines, with
each such part on a separate output line. Output lines use the
same delimiters as input, and delimiters are null bytes if '-z'
('--null-data') is also used (*note Other Options::).
'-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. ('-q' is
specified by POSIX.)
'-s'
'--no-messages'
Suppress error messages about nonexistent or unreadable files.
Portability note: unlike GNU 'grep', 7th Edition Unix 'grep' did
not conform to POSIX, because it lacked '-q' and its '-s' option
behaved like GNU 'grep''s '-q' option.(1) USG-style 'grep' also
lacked '-q' but its '-s' option behaved like GNU 'grep''s.
Portable shell scripts should avoid both '-q' and '-s' and should
redirect standard and error output to '/dev/null' instead. ('-s'
is specified by POSIX.)
---------- Footnotes ----------
(1) Of course, 7th Edition Unix predated POSIX by several years!
File: grep.info-t, Node: Output Line Prefix Control, Next: Context Line Control, Prev: General Output Control, Up: Command-line Options
2.1.4 Output Line Prefix Control
--------------------------------
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.
'-b'
'--byte-offset'
Print the 0-based byte offset within the input file before each
line of output. If '-o' ('--only-matching') is specified, print
the offset of the matching part itself.
'-H'
'--with-filename'
Print the file name for each match. This is the default when there
is more than one file to search.
'-h'
'--no-filename'
Suppress the prefixing of file names on output. This is the
default when there is only one file (or only standard input) to
search.
'--label=LABEL'
Display input actually coming from standard input as input coming
from file LABEL. This is especially useful when implementing tools
like 'zgrep'; e.g.:
gzip -cd foo.gz | grep --label=foo -H something
'-n'
'--line-number'
Prefix each line of output with the 1-based line number within its
input file. ('-n' is specified by POSIX.)
'-T'
'--initial-tab'
Make sure that the first character of actual line content lies on a
tab stop, so that the alignment of tabs looks normal. This is
useful with options that prefix their output to the actual content:
'-H', '-n', and '-b'. This may also prepend spaces to output line
numbers and byte offsets so that lines from a single file all start
at the same column.
'-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.
File: grep.info-t, Node: Context Line Control, Next: File and Directory Selection, Prev: Output Line Prefix Control, Up: Command-line Options
2.1.5 Context Line Control
--------------------------
"Context lines" are non-matching lines that are near a matching line.
They are output only if one of the following options are used.
Regardless of how these options are set, 'grep' never outputs any given
line more than once. If the '-o' ('--only-matching') option is
specified, these options have no effect and a warning is given upon
their use.
'-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'
'-NUM'
'--context=NUM'
Print NUM lines of leading and trailing output context.
'--group-separator=STRING'
When '-A', '-B' or '-C' are in use, print STRING instead of '--'
between groups of lines.
'--no-group-separator'
When '-A', '-B' or '-C' are in use, do not print a separator
between groups of lines.
Here are some points about how 'grep' chooses the separator to print
between prefix fields and line content:
* Matching lines normally use ':' as a separator between prefix
fields and actual line content.
* Context (i.e., non-matching) lines use '-' instead.
* When context is not specified, matching lines are simply output one
right after another.
* When context is specified, lines that are adjacent in the input
form a group and are output one right after another, while by
default a separator appears between non-adjacent groups.
* The default separator is a '--' line; its presence and appearance
can be changed with the options above.
* Each group may contain several matching lines when they are close
enough to each other that two adjacent groups connect and can merge
into a single contiguous one.
File: grep.info-t, Node: File and Directory Selection, Next: Other Options, Prev: Context Line Control, Up: Command-line Options
2.1.6 File and Directory Selection
----------------------------------
'-a'
'--text'
Process a binary file as if it were text; this is equivalent to the
'--binary-files=text' option.
'--binary-files=TYPE'
If a file's data or metadata indicate that the file contains binary
data, assume that the file is of type TYPE. Non-text bytes
indicate binary data; these are either output bytes that are
improperly encoded for the current locale (*note Environment
Variables::), or null input bytes when the '-z' ('--null-data')
option is not given (*note Other Options::).
By default, TYPE is 'binary', and 'grep' suppresses output after
null input binary data is discovered, and suppresses output lines
that contain improperly encoded data. When some output is
suppressed, 'grep' follows any output with a one-line message
saying that a binary file matches.
If TYPE is 'without-match', when 'grep' discovers null input binary
data it assumes that the rest of the file does not match; this is
equivalent to the '-I' option.
If TYPE is 'text', 'grep' processes binary data as if it were text;
this is equivalent to the '-a' option.
When TYPE is 'binary', 'grep' may treat non-text bytes as line
terminators even without the '-z' ('--null-data') option. This
means choosing 'binary' versus 'text' can affect whether a pattern
matches a file. For example, when TYPE is 'binary' the pattern
'q$' might match 'q' immediately followed by a null byte, even
though this is not matched when TYPE is 'text'. Conversely, when
TYPE is 'binary' the pattern '.' (period) might not match a null
byte.
_Warning:_ The '-a' ('--binary-files=text') option might output
binary garbage, which can have nasty side effects if the output is
a terminal and if the terminal driver interprets some of it as
commands. On the other hand, when reading files whose text
encodings are unknown, it can be helpful to use '-a' or to set
'LC_ALL='C'' in the environment, in order to find more matches even
if the matches are unsafe for direct display.
'-D ACTION'
'--devices=ACTION'
If an input file is a device, FIFO, or socket, use ACTION to
process it. If ACTION is 'read', all devices are read just as if
they were ordinary files. If ACTION is 'skip', devices, FIFOs, and
sockets are silently skipped. By default, devices are read if they
are on the command line or if the '-R' ('--dereference-recursive')
option is used, and are skipped if they are encountered recursively
and the '-r' ('--recursive') option is used. This option has no
effect on a file that is read via standard input.
'-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
file systems 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, following
command-line symbolic links and skipping other symlinks; this is
equivalent to the '-r' option.
'--exclude=GLOB'
Skip any command-line file with a name suffix that matches the
pattern GLOB, using wildcard matching; a name suffix is either the
whole name, or any suffix starting after a '/' and before a
non-'/'. When searching recursively, skip any subfile whose base
name matches GLOB; the base name is the part after the last '/'. A
pattern can use '*', '?', and '['...']' as wildcards, and '\' to
quote a wildcard or backslash character literally.
'--exclude-from=FILE'
Skip files whose name matches any of the patterns read from FILE
(using wildcard matching as described under '--exclude').
'--exclude-dir=GLOB'
Skip any command-line directory with a name suffix that matches the
pattern GLOB. When searching recursively, skip any subdirectory
whose base name matches GLOB. Ignore any redundant trailing
slashes in GLOB.
'-I'
Process a binary file as if it did not contain matching data; this
is equivalent to the '--binary-files=without-match' option.
'--include=GLOB'
Search only files whose name matches GLOB, using wildcard matching
as described under '--exclude'.
'-r'
'--recursive'
For each directory operand, read and process all files in that
directory, recursively. Follow symbolic links on the command line,
but skip symlinks that are encountered recursively. Note that if
no file operand is given, grep searches the working directory.
This is the same as the '--directories=recurse' option.
'-R'
'--dereference-recursive'
For each directory operand, read and process all files in that
directory, recursively, following all symbolic links.
File: grep.info-t, Node: Other Options, Prev: File and Directory Selection, Up: Command-line Options
2.1.7 Other Options
-------------------
'--line-buffered'
Use line buffering on output. This can cause a performance
penalty.
'-U'
'--binary'
On platforms that distinguish between text and binary I/O, use the
latter when reading and writing files other than the user's
terminal, so that all input bytes are read and written as-is. This
overrides the default behavior where 'grep' follows the operating
system's advice whether to use text or binary I/O. On MS-Windows
when 'grep' uses text I/O it reads a carriage return-newline pair
as a newline and a Control-Z as end-of-file, and it writes a
newline as a carriage return-newline pair.
When using text I/O '--byte-offset' ('-b') counts and
'--binary-files' heuristics apply to input data after text-I/O
processing. Also, the '--binary-files' heuristics need not agree
with the '--binary' option; that is, they may treat the data as
text even if '--binary' is given, or vice versa. *Note File and
Directory Selection::.
This option has no effect on GNU and other POSIX-compatible
platforms, which do not distinguish text from binary I/O.
'-z'
'--null-data'
Treat input and output data as sequences of lines, each terminated
by a zero byte (the ASCII NUL character) instead of a newline.
Like the '-Z' or '--null' option, this option can be used with
commands like 'sort -z' to process arbitrary file names.
File: grep.info-t, Node: Environment Variables, Next: Exit Status, Prev: Command-line Options, Up: Invoking
2.2 Environment Variables
=========================
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_COLLATE' is set to 'pt_BR',
then the Brazilian Portuguese locale is used for the 'LC_COLLATE'
category. As a special case for 'LC_MESSAGES' only, the environment
variable 'LANGUAGE' can contain a colon-separated list of languages that
overrides the three environment variables that ordinarily specify 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). The
shell command 'locale -a' lists locales that are currently available.
Many of the environment variables in the following list let you
control highlighting using Select Graphic Rendition (SGR) commands
interpreted by the terminal or terminal emulator. (See the section in
the documentation of your text terminal for permitted values and their
meanings 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.
The two-letter names used in the 'GREP_COLORS' environment variable
(and some of the others) refer to terminal "capabilities," the ability
of a terminal to highlight text, or change its color, and so on. These
capabilities are stored in an online database and accessed by the
'terminfo' library.
'GREP_OPTIONS'
This variable specifies default options to be placed in front of
any explicit options. As this causes problems when writing
portable scripts, this feature will be removed in a future release
of 'grep', and 'grep' warns if it is used. Please use an alias or
script instead. For example, if 'grep' is in the directory
'/usr/bin' you can prepend '$HOME/bin' to your 'PATH' and create an
executable script '$HOME/bin/grep' containing the following:
#! /bin/sh
export PATH=/usr/bin
exec grep --color=auto --devices=skip "$@"
'GREP_COLOR'
This variable specifies the color used to highlight matched
(non-empty) text. It is deprecated in favor of '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.
'GREP_COLORS'
This variable specifies the colors and other attributes used to
highlight various parts of the output. Its value is a
colon-separated list of 'terminfo' capabilities that defaults to
'ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36' with the 'rv'
and 'ne' boolean capabilities omitted (i.e., false). Supported
capabilities are as follows.
'sl='
SGR substring for whole selected lines (i.e., matching lines
when the '-v' command-line option is omitted, or non-matching
lines when '-v' is specified). If however the boolean 'rv'
capability and the '-v' command-line option are both
specified, it applies to context matching lines instead. The
default is empty (i.e., the terminal's default color pair).
'cx='
SGR substring for whole context lines (i.e., non-matching
lines when the '-v' command-line option is omitted, or
matching lines when '-v' is specified). If however the
boolean 'rv' capability and the '-v' command-line option are
both specified, it applies to selected non-matching lines
instead. The default is empty (i.e., the terminal's default
color pair).
'rv'
Boolean value that reverses (swaps) the meanings of the 'sl='
and 'cx=' capabilities when the '-v' command-line option is
specified. The default is false (i.e., the capability is
omitted).
'mt=01;31'
SGR substring for matching non-empty text in any matching line
(i.e., a selected line when the '-v' command-line option is
omitted, or a context line when '-v' is specified). Setting
this is equivalent to setting both 'ms=' and 'mc=' at once to
the same value. The default is a bold red text foreground
over the current line background.
'ms=01;31'
SGR substring for matching non-empty text in a selected line.
(This is used only when the '-v' command-line option is
omitted.) The effect of the 'sl=' (or 'cx=' if 'rv')
capability remains active when this takes effect. The default
is a bold red text foreground over the current line
background.
'mc=01;31'
SGR substring for matching non-empty text in a context line.
(This is used only when the '-v' command-line option is
specified.) The effect of the 'cx=' (or 'sl=' if 'rv')
capability remains active when this takes effect. The default
is a bold red text foreground over the current line
background.
'fn=35'
SGR substring for file names prefixing any content line. The
default is a magenta text foreground over the terminal's
default background.
'ln=32'
SGR substring for line numbers prefixing any content line.
The default is a green text foreground over the terminal's
default background.
'bn=32'
SGR substring for byte offsets prefixing any content line.
The default is a green text foreground over the terminal's
default background.
'se=36'
SGR substring for separators that are inserted between
selected line fields (':'), between context line fields ('-'),
and between groups of adjacent lines when nonzero context is
specified ('--'). The default is a cyan text foreground over
the terminal's default background.
'ne'
Boolean value that prevents clearing to the end of line using
Erase in Line (EL) to Right ('\33[K') each time a colorized
item ends. This is needed on terminals on which EL is not
supported. It is otherwise useful on terminals for which the
'back_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.
'LC_ALL'
'LC_COLLATE'
'LANG'
These variables specify the locale for the 'LC_COLLATE' category,
which might affect how range expressions like '[a-z]' are
interpreted.
'LC_ALL'
'LC_CTYPE'
'LANG'
These variables specify the locale for the 'LC_CTYPE' category,
which determines the type of characters, e.g., which characters are
whitespace. This category also determines the character encoding,
that is, whether text is encoded in UTF-8, ASCII, or some other
encoding. In the 'C' or 'POSIX' locale, all characters are encoded
as a single byte and every byte is a valid character.
'LANGUAGE'
'LC_ALL'
'LC_MESSAGES'
'LANG'
These variables specify the locale for the 'LC_MESSAGES' category,
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 requires; otherwise, 'grep' behaves
more like other GNU programs. POSIX 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, 'POSIXLY_CORRECT' disables special
handling of an invalid bracket expression. *Note
invalid-bracket-expr::.
'_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.info-t, Node: Exit Status, Next: grep Programs, Prev: Environment Variables, Up: Invoking
2.3 Exit Status
===============
Normally the exit status is 0 if a line is selected, 1 if no lines were
selected, and 2 if an error occurred. However, if the '-q' or '--quiet'
or '--silent' option is used and a line is selected, the exit status is
0 even if an error occurred. Other 'grep' implementations may exit with
status greater than 2 on error.
File: grep.info-t, Node: grep Programs, Prev: Exit Status, Up: Invoking
2.4 'grep' Programs
===================
'grep' searches the named input files for lines containing a match to
the given pattern. By default, 'grep' prints the matching lines. A
file named '-' stands for standard input. If no input is specified,
'grep' searches the working directory '.' if given a command-line option
specifying recursion; otherwise, 'grep' searches standard input. There
are four major variants of 'grep', controlled by the following options.
'-G'
'--basic-regexp'
Interpret the pattern as a basic regular expression (BRE). This is
the default.
'-E'
'--extended-regexp'
Interpret the pattern as an extended regular expression (ERE).
('-E' is specified by POSIX.)
'-F'
'--fixed-strings'
Interpret the pattern as a list of fixed strings (instead of
regular expressions), separated by newlines, any of which is to be
matched. ('-F' is specified by POSIX.)
'-P'
'--perl-regexp'
Interpret the pattern as a Perl-compatible regular expression
(PCRE). This is experimental, particularly when combined with the
'-z' ('--null-data') option, and 'grep -P' may warn of
unimplemented features. *Note Other 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.
File: grep.info-t, Node: Regular Expressions, Next: Usage, Prev: Invoking, Up: Top
3 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 three different versions of regular expression
syntax: basic (BRE), extended (ERE), and Perl-compatible (PCRE). In GNU
'grep', there is no difference in available functionality between the
basic and extended syntaxes. In other implementations, basic regular
expressions are less powerful. The following description applies to
extended regular expressions; differences for basic regular expressions
are summarized afterwards. Perl-compatible regular expressions give
additional functionality, and are documented in the pcresyntax(3) and
pcrepattern(3) manual pages, but work only if PCRE is available in the
system.
* Menu:
* Fundamental Structure::
* Character Classes and Bracket Expressions::
* The Backslash Character and Special Expressions::
* Anchoring::
* Back-references and Subexpressions::
* Basic vs Extended::
File: grep.info-t, Node: Fundamental Structure, Next: Character Classes and Bracket Expressions, Up: Regular Expressions
3.1 Fundamental Structure
=========================
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:
'.'
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.
'{,M}'
The preceding item is matched at most M times. This is a GNU
extension.
'{N,M}'
The preceding item is matched at least N times, but not more than M
times.
The empty regular expression matches the empty string. 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
alternate 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.
An unmatched ')' matches just itself.
File: grep.info-t, Node: Character Classes and Bracket Expressions, Next: The Backslash Character and Special Expressions, Prev: Fundamental Structure, Up: Regular Expressions
3.2 Character Classes and Bracket Expressions
=============================================
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. In the default C locale,
the sorting sequence is the native character order; for example, '[a-d]'
is equivalent to '[abcd]'. In other locales, the sorting sequence is
not specified, and '[a-d]' might be equivalent to '[abcd]' or to
'[aBbCcDd]', or it might fail to match any character, or the set of
characters that it matches might even be erratic. 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; for example, '[[:alnum:]]' means the character class
of numbers and letters in the current locale.
'[:alnum:]'
Alphanumeric characters: '[:alpha:]' and '[:digit:]'; in the 'C'
locale and ASCII character encoding, this is the same as
'[0-9A-Za-z]'.
'[:alpha:]'
Alphabetic characters: '[:lower:]' and '[:upper:]'; in the 'C'
locale and ASCII character encoding, this is the same as
'[A-Za-z]'.
'[: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; in the 'C' locale and ASCII character encoding,
this is '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; in the 'C' locale and ASCII character
encoding, this is '! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \
] ^ _ ` { | } ~'.
'[:space:]'
Space characters: in the 'C' locale, this is tab, newline, vertical
tab, form feed, carriage return, and space. *Note Usage::, for
more discussion of matching newlines.
'[:upper:]'
Upper-case letters: in the 'C' locale and ASCII character encoding,
this is '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'.
Note that the brackets in these class names are part of the symbolic
names, and must be included in addition to the brackets delimiting the
bracket expression.
If you mistakenly omit the outer brackets, and search for say,
'[:upper:]', GNU 'grep' prints a diagnostic and exits with status 2, on
the assumption that you did not intend to search for the nominally
equivalent regular expression: '[:epru]'. Set the 'POSIXLY_CORRECT'
environment variable to disable this feature.
Most meta-characters lose their special meaning inside bracket
expressions.
']'
ends the bracket expression 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 symbol, and should be followed
by a valid character class name.
':]'
represents the close character class symbol.
'-'
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.
File: grep.info-t, Node: The Backslash Character and Special Expressions, Next: Anchoring, Prev: Character Classes and Bracket Expressions, Up: Regular Expressions
3.3 The Backslash Character and Special Expressions
===================================================
The '\' character, when followed by certain ordinary characters, takes 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:]]'.
'\s'
Match whitespace, it is a synonym for '[[:space:]]'.
'\S'
Match non-whitespace, it is a synonym for '[^[:space:]]'.
For example, '\brat\b' matches the separate word 'rat', '\Brat\B'
matches 'crate' but not 'furry rat'.
File: grep.info-t, Node: Anchoring, Next: Back-references and Subexpressions, Prev: The Backslash Character and Special Expressions, Up: Regular Expressions
3.4 Anchoring
=============
The caret '^' and the dollar sign '$' are meta-characters that
respectively match the empty string at the beginning and end of a line.
They are termed "anchors", since they force the match to be "anchored"
to beginning or end of a line, respectively.
File: grep.info-t, Node: Back-references and Subexpressions, Next: Basic vs Extended, Prev: Anchoring, Up: Regular Expressions
3.5 Back-references and Subexpressions
======================================
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.
File: grep.info-t, Node: Basic vs Extended, Prev: Back-references and Subexpressions, Up: Regular Expressions
3.6 Basic vs Extended Regular Expressions
=========================================
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 allows this behavior as an extension, but
portable scripts should avoid it.
File: grep.info-t, Node: Usage, Next: Performance, Prev: Regular Expressions, Up: Top
4 Usage
*******
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. *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 '/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 -H 'hello' *.c
which merely looks for 'hello' in all files in the current
directory whose names end in '.c'. The 'find ...' command line
above is more similar to the command:
grep -rH --include='*.c' 'hello' /home/gigi
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:x:2098:1000:Eli Smith:/home/eli:/bin/bash
Alternatively, use '-H', which is a GNU extension:
grep -H 'eli' /etc/passwd
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 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.
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 non-matching 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. Why does the empty pattern match every input line?
The 'grep' command searches for lines that contain strings that
match a pattern. Every line contains the empty string, so an empty
pattern causes 'grep' to find a match on each line. It is not the
only such pattern: '^', '$', '.*', and many other patterns cause
'grep' to match every line.
To match empty lines, use the pattern '^$'. To match blank lines,
use the pattern '^[[:blank:]]*$'. To match no lines at all, use
the command 'grep -f /dev/null'.
12. How can I search in both standard input and in files?
Use the special file name '-':
cat /etc/passwd | grep 'alain' - /etc/motd
13. How to express palindromes in a regular expression?
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'.
14. Why is this back-reference failing?
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.)
15. How can I match across lines?
Standard grep cannot do this, as it is fundamentally line-based.
Therefore, merely using the '[:space:]' character class does not
match newlines in the way you might expect.
With the GNU 'grep' option '-z' ('--null-data'), each input and
output "line" is null-terminated; *note Other Options::. Thus, you
can match newlines in the input, but typically if there is a match
the entire input is output, so this usage is often combined with
output-suppressing options like '-q', e.g.:
printf 'foo\nbar\n' | grep -z -q 'foo[[:space:]]\+bar'
If this does not suffice, you can transform the input before giving
it to 'grep', or turn to 'awk', 'sed', 'perl', or many other
utilities that are designed to operate across lines.
16. What do 'grep', 'fgrep', and 'egrep' stand for?
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'.
File: grep.info-t, Node: Performance, Next: Reporting Bugs, Prev: Usage, Up: Top
5 Performance
*************
Typically 'grep' is an efficient way to search text. However, it can be
quite slow in some cases, and it can search large files where even minor
performance tweaking can help significantly. Although the algorithm
used by 'grep' is an implementation detail that can change from release
to release, understanding its basic strengths and weaknesses can help
you improve its performance.
The 'grep' command operates partly via a set of automata that are
designed for efficiency, and partly via a slower matcher that takes over
when the fast matchers run into unusual features like back-references.
When feasible, the Boyer-Moore fast string searching algorithm is used
to match a single fixed pattern, and the Aho-Corasick algorithm is used
to match multiple fixed patterns.
Generally speaking 'grep' operates more efficiently in single-byte
locales, since it can avoid the special processing needed for multi-byte
characters. If your pattern will work just as well that way, setting
'LC_ALL' to a single-byte locale can help performance considerably.
Setting 'LC_ALL='C'' can be particularly efficient, as 'grep' is tuned
for that locale.
Outside the 'C' locale, case-insensitive search, and search for
bracket expressions like '[a-z]' and '[[=a=]b]', can be surprisingly
inefficient due to difficulties in fast portable access to concepts like
multi-character collating elements.
A back-reference such as '\1' can hurt performance significantly in
some cases, since back-references cannot in general be implemented via a
finite state automaton, and instead trigger a backtracking algorithm
that can be quite inefficient. For example, although the pattern
'^(.*)\1{14}(.*)\2{13}$' matches only lines whose lengths can be written
as a sum 15x + 14y for nonnegative integers x and y, the pattern matcher
does not perform linear Diophantine analysis and instead backtracks
through all possible matching strings, using an algorithm that is
exponential in the worst case.
On some operating systems that support files with holes--large regions
of zeros that are not physically present on secondary storage--'grep' can
skip over the holes efficiently without needing to read the zeros. This
optimization is not available if the '-a' ('--text') option is used
(*note File and Directory Selection::), unless the '-z' ('--null-data')
option is also used (*note Other Options::).
For more about the algorithms used by 'grep' and about related string
matching algorithms, see:
* Aho AV. Algorithms for finding patterns in strings. In: van Leeuwen
J. _Handbook of Theoretical Computer Science_, vol. A. New York:
Elsevier; 1990. p. 255-300. This surveys classic string matching
algorithms, some of which are used by 'grep'.
* Aho AV, Corasick MJ. Efficient string matching: an aid to
bibliographic search. _CACM_. 1975;18(6):333-40.
<http://dx.doi.org/10.1145/360825.360855>;. This introduces the
Aho-Corasick algorithm.
* Boyer RS, Moore JS. A fast string searching algorithm. _CACM_.
1977;20(10):762-72. <http://dx.doi.org/10.1145/359842.359859>;. This
introduces the Boyer-Moore algorithm.
* Faro S, Lecroq T. The exact online string matching problem: a
review of the most recent results. _ACM Comput Surv_.
2013;45(2):13. <http://dx.doi.org/10.1145/2431211.2431212>;. This
surveys string matching algorithms that might help improve the
performance of 'grep' in the future.
File: grep.info-t, Node: Reporting Bugs, Next: Copying, Prev: Performance, Up: Top
6 Reporting bugs
****************
Bug reports can be found at the GNU bug report logs for 'grep'
(http://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep). If you find a
bug not listed there, please email it to <bug-grep AT gnu.org> to create a
new bug report.
6.1 Known Bugs
==============
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.info-t, Node: Copying, Next: Index, Prev: Reporting Bugs, Up: Top
7 Copying
*********
GNU 'grep' is licensed under the GNU GPL, which makes it "free
software".
The "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". In short, you have the right (freedom) to run and
change 'grep' and distribute it to other people, and--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 general method of licensing software is sometimes called "open
source". The GNU project prefers the term "free software" for reasons
outlined at
<http://www.gnu.org/philosophy/open-source-misses-the-point.html>;.
This manual is free documentation in the same sense. The
documentation license is included below. The license for the program is
available with the source code, or at
<http://www.gnu.org/licenses/gpl.html>;.
* Menu:
* GNU Free Documentation License::
File: grep.info-t, Node: GNU Free Documentation License, Up: Copying
7.1 GNU Free Documentation License
==================================
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
<http://fsf.org/>;
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
functional and useful 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, in any medium,
that contains a notice placed by the copyright holder saying it can
be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You accept
the license if you copy, modify or distribute the work in a way
requiring permission under copyright law.
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. (Thus, 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.
If a section does not fit the above definition of Secondary then it
is not allowed to be designated as Invariant. The Document may
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any Invariant Sections then there are none.
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
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
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A "Transparent" copy of the Document means a machine-readable copy,
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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.
The "publisher" means any person or entity that distributes copies
of the Document to the public.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
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 (or copies in media that commonly
have printed covers) 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 computer-network location from which the general
network-using public has access to download using public-standard
network protocols a complete Transparent copy of the Document, free
of added material. 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 fewer than five), unless they release you
from this requirement.
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", Preserve 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. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, 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 to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
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.
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
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
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."
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, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
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 half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
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, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly and
finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from you
under this License. If your rights have been terminated and not
permanently reinstated, receipt of a copy of some or all of the
same material does not give you any rights to use it.
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. If the Document specifies that a proxy can
decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
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 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
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.info-t, Node: Index, Prev: Copying, Up: Top
Index
*****
* Menu:
* *: Fundamental Structure.
(line 21)
* +: Fundamental Structure.
(line 24)
* --after-context: Context Line Control.
(line 15)
* --basic-regexp: grep Programs. (line 15)
* --before-context: Context Line Control.
(line 19)
* --binary: Other Options. (line 12)
* --binary-files: File and Directory Selection.
(line 12)
* --byte-offset: Output Line Prefix Control.
(line 12)
* --color: General Output Control.
(line 14)
* --colour: General Output Control.
(line 14)
* --context: Context Line Control.
(line 24)
* --count: General Output Control.
(line 8)
* --dereference-recursive: File and Directory Selection.
(line 109)
* --devices: File and Directory Selection.
(line 51)
* --directories: File and Directory Selection.
(line 62)
* --exclude: File and Directory Selection.
(line 73)
* --exclude-dir: File and Directory Selection.
(line 86)
* --exclude-from: File and Directory Selection.
(line 82)
* --extended-regexp: grep Programs. (line 20)
* --file: Matching Control. (line 14)
* --files-with-matches: General Output Control.
(line 35)
* --files-without-match: General Output Control.
(line 29)
* --fixed-strings: grep Programs. (line 25)
* --group-separator: Context Line Control.
(line 27)
* --group-separator <1>: Context Line Control.
(line 31)
* --help: Generic Program Information.
(line 7)
* --ignore-case: Matching Control. (line 23)
* --include: File and Directory Selection.
(line 96)
* --initial-tab: Output Line Prefix Control.
(line 41)
* --invert-match: Matching Control. (line 42)
* --label: Output Line Prefix Control.
(line 28)
* --line-buffered: Other Options. (line 7)
* --line-number: Output Line Prefix Control.
(line 36)
* --line-regexp: Matching Control. (line 57)
* --max-count: General Output Control.
(line 42)
* --no-filename: Output Line Prefix Control.
(line 23)
* --no-messages: General Output Control.
(line 87)
* --null: Output Line Prefix Control.
(line 50)
* --null-data: Other Options. (line 33)
* --only-matching: General Output Control.
(line 72)
* --perl-regexp: grep Programs. (line 31)
* --quiet: General Output Control.
(line 80)
* --recursive: File and Directory Selection.
(line 101)
* --regexp=PATTERN: Matching Control. (line 8)
* --silent: General Output Control.
(line 80)
* --text: File and Directory Selection.
(line 8)
* --version: Generic Program Information.
(line 12)
* --with-filename: Output Line Prefix Control.
(line 18)
* --word-regexp: Matching Control. (line 47)
* -A: Context Line Control.
(line 15)
* -a: File and Directory Selection.
(line 8)
* -b: Output Line Prefix Control.
(line 12)
* -B: Context Line Control.
(line 19)
* -c: General Output Control.
(line 8)
* -C: Context Line Control.
(line 24)
* -D: File and Directory Selection.
(line 51)
* -d: File and Directory Selection.
(line 62)
* -e: Matching Control. (line 8)
* -E: grep Programs. (line 20)
* -f: Matching Control. (line 14)
* -F: grep Programs. (line 25)
* -G: grep Programs. (line 15)
* -H: Output Line Prefix Control.
(line 18)
* -h: Output Line Prefix Control.
(line 23)
* -i: Matching Control. (line 23)
* -L: General Output Control.
(line 29)
* -l: General Output Control.
(line 35)
* -m: General Output Control.
(line 42)
* -n: Output Line Prefix Control.
(line 36)
* -NUM: Context Line Control.
(line 24)
* -o: General Output Control.
(line 72)
* -P: grep Programs. (line 31)
* -q: General Output Control.
(line 80)
* -r: File and Directory Selection.
(line 101)
* -R: File and Directory Selection.
(line 109)
* -s: General Output Control.
(line 87)
* -T: Output Line Prefix Control.
(line 41)
* -U: Other Options. (line 12)
* -V: Generic Program Information.
(line 12)
* -v: Matching Control. (line 42)
* -w: Matching Control. (line 47)
* -x: Matching Control. (line 57)
* -y: Matching Control. (line 23)
* -Z: Output Line Prefix Control.
(line 50)
* -z: Other Options. (line 33)
* .: Fundamental Structure.
(line 15)
* ?: Fundamental Structure.
(line 18)
* _N_GNU_nonoption_argv_flags_ environment variable: Environment Variables.
(line 193)
* {,M}: Fundamental Structure.
(line 33)
* {N,M}: Fundamental Structure.
(line 37)
* {N,}: Fundamental Structure.
(line 30)
* {N}: Fundamental Structure.
(line 27)
* after context: Context Line Control.
(line 15)
* alnum character class: Character Classes and Bracket Expressions.
(line 29)
* alpha character class: Character Classes and Bracket Expressions.
(line 34)
* alphabetic characters: Character Classes and Bracket Expressions.
(line 34)
* alphanumeric characters: Character Classes and Bracket Expressions.
(line 29)
* anchoring: Anchoring. (line 6)
* asterisk: Fundamental Structure.
(line 21)
* back-reference: Back-references and Subexpressions.
(line 6)
* back-references: Performance. (line 32)
* backslash: The Backslash Character and Special Expressions.
(line 6)
* basic regular expressions: Basic vs Extended. (line 6)
* before context: Context Line Control.
(line 19)
* binary files: File and Directory Selection.
(line 8)
* binary files <1>: File and Directory Selection.
(line 12)
* binary I/O: Other Options. (line 12)
* blank character class: Character Classes and Bracket Expressions.
(line 39)
* blank characters: Character Classes and Bracket Expressions.
(line 39)
* bn GREP_COLORS capability: Environment Variables.
(line 134)
* braces, first argument omitted: Fundamental Structure.
(line 33)
* braces, one argument: Fundamental Structure.
(line 27)
* braces, second argument omitted: Fundamental Structure.
(line 30)
* braces, two arguments: Fundamental Structure.
(line 37)
* bracket expression: Character Classes and Bracket Expressions.
(line 6)
* Bugs, known: Reporting Bugs. (line 14)
* bugs, reporting: Reporting Bugs. (line 6)
* byte offset: Output Line Prefix Control.
(line 12)
* case insensitive search: Matching Control. (line 23)
* case insensitive search <1>: Performance. (line 27)
* changing name of standard input: Output Line Prefix Control.
(line 28)
* character class: Character Classes and Bracket Expressions.
(line 6)
* character classes: Character Classes and Bracket Expressions.
(line 28)
* character type: Environment Variables.
(line 161)
* classes of characters: Character Classes and Bracket Expressions.
(line 28)
* cntrl character class: Character Classes and Bracket Expressions.
(line 42)
* context lines: General Output Control.
(line 64)
* context lines <1>: Context Line Control.
(line 6)
* context lines <2>: Context Line Control.
(line 24)
* context lines, after match: Context Line Control.
(line 15)
* context lines, before match: Context Line Control.
(line 19)
* control characters: Character Classes and Bracket Expressions.
(line 42)
* copying: Copying. (line 6)
* counting lines: General Output Control.
(line 8)
* cx GREP_COLORS capability: Environment Variables.
(line 85)
* default options environment variable: Environment Variables.
(line 45)
* device search: File and Directory Selection.
(line 51)
* digit character class: Character Classes and Bracket Expressions.
(line 47)
* digit characters: Character Classes and Bracket Expressions.
(line 47)
* directory search: File and Directory Selection.
(line 62)
* dot: Fundamental Structure.
(line 15)
* environment variables: Environment Variables.
(line 44)
* exclude directories: File and Directory Selection.
(line 86)
* exclude files: File and Directory Selection.
(line 73)
* exclude files <1>: File and Directory Selection.
(line 82)
* exit status: Exit Status. (line 6)
* FAQ about grep usage: Usage. (line 17)
* files which don't match: General Output Control.
(line 29)
* fn GREP_COLORS capability: Environment Variables.
(line 124)
* fn GREP_COLORS capability <1>: Environment Variables.
(line 139)
* graph character class: Character Classes and Bracket Expressions.
(line 50)
* graphic characters: Character Classes and Bracket Expressions.
(line 50)
* grep programs: grep Programs. (line 6)
* GREP_COLOR environment variable: Environment Variables.
(line 58)
* GREP_COLORS environment variable: Environment Variables.
(line 69)
* GREP_OPTIONS environment variable: Environment Variables.
(line 45)
* group separator: Context Line Control.
(line 27)
* group separator <1>: Context Line Control.
(line 31)
* hexadecimal digits: Character Classes and Bracket Expressions.
(line 74)
* highlight markers: Environment Variables.
(line 58)
* highlight markers <1>: Environment Variables.
(line 69)
* highlight, color, colour: General Output Control.
(line 14)
* holes in files: Performance. (line 42)
* include files: File and Directory Selection.
(line 96)
* interval specifications: Basic vs Extended. (line 10)
* invert matching: Matching Control. (line 42)
* LANG environment variable: Environment Variables.
(line 9)
* LANG environment variable <1>: Environment Variables.
(line 161)
* LANG environment variable <2>: Environment Variables.
(line 168)
* LANG environment variable <3>: Environment Variables.
(line 179)
* LANGUAGE environment variable: Environment Variables.
(line 9)
* LANGUAGE environment variable <1>: Environment Variables.
(line 179)
* language of messages: Environment Variables.
(line 179)
* LC_ALL environment variable: Environment Variables.
(line 9)
* LC_ALL environment variable <1>: Environment Variables.
(line 161)
* LC_ALL environment variable <2>: Environment Variables.
(line 168)
* LC_ALL environment variable <3>: Environment Variables.
(line 179)
* LC_COLLATE environment variable: Environment Variables.
(line 161)
* LC_CTYPE environment variable: Environment Variables.
(line 168)
* LC_MESSAGES environment variable: Environment Variables.
(line 9)
* LC_MESSAGES environment variable <1>: Environment Variables.
(line 179)
* line buffering: Other Options. (line 7)
* line numbering: Output Line Prefix Control.
(line 36)
* ln GREP_COLORS capability: Environment Variables.
(line 129)
* locales: Performance. (line 20)
* lower character class: Character Classes and Bracket Expressions.
(line 53)
* lower-case letters: Character Classes and Bracket Expressions.
(line 53)
* match expression at most M times: Fundamental Structure.
(line 33)
* match expression at most once: Fundamental Structure.
(line 18)
* match expression from N to M times: Fundamental Structure.
(line 37)
* match expression N or more times: Fundamental Structure.
(line 30)
* match expression N times: Fundamental Structure.
(line 27)
* match expression one or more times: Fundamental Structure.
(line 24)
* match expression zero or more times: Fundamental Structure.
(line 21)
* match the whole line: Matching Control. (line 57)
* matching basic regular expressions: grep Programs. (line 15)
* matching extended regular expressions: grep Programs. (line 20)
* matching fixed strings: grep Programs. (line 25)
* matching Perl-compatible regular expressions: grep Programs.
(line 31)
* matching whole words: Matching Control. (line 47)
* max-count: General Output Control.
(line 42)
* mc GREP_COLORS capability: Environment Variables.
(line 116)
* message language: Environment Variables.
(line 179)
* ms GREP_COLORS capability: Environment Variables.
(line 108)
* MS-Windows binary I/O: Other Options. (line 12)
* mt GREP_COLORS capability: Environment Variables.
(line 100)
* names of matching files: General Output Control.
(line 35)
* national language support: Environment Variables.
(line 161)
* national language support <1>: Environment Variables.
(line 179)
* ne GREP_COLORS capability: Environment Variables.
(line 146)
* NLS: Environment Variables.
(line 161)
* no filename prefix: Output Line Prefix Control.
(line 23)
* numeric characters: Character Classes and Bracket Expressions.
(line 47)
* only matching: General Output Control.
(line 72)
* palindromes: Usage. (line 139)
* pattern from file: Matching Control. (line 14)
* pattern list: Matching Control. (line 8)
* performance: Performance. (line 6)
* period: Fundamental Structure.
(line 15)
* plus sign: Fundamental Structure.
(line 24)
* POSIXLY_CORRECT environment variable: Environment Variables.
(line 184)
* print character class: Character Classes and Bracket Expressions.
(line 57)
* print non-matching lines: Matching Control. (line 42)
* printable characters: Character Classes and Bracket Expressions.
(line 57)
* punct character class: Character Classes and Bracket Expressions.
(line 60)
* punctuation characters: Character Classes and Bracket Expressions.
(line 60)
* question mark: Fundamental Structure.
(line 18)
* quiet, silent: General Output Control.
(line 80)
* range expression: Character Classes and Bracket Expressions.
(line 12)
* recursive search: File and Directory Selection.
(line 101)
* recursive search <1>: File and Directory Selection.
(line 109)
* regular expressions: Regular Expressions. (line 6)
* return status: Exit Status. (line 6)
* rv GREP_COLORS capability: Environment Variables.
(line 94)
* searching directory trees: File and Directory Selection.
(line 73)
* searching directory trees <1>: File and Directory Selection.
(line 82)
* searching directory trees <2>: File and Directory Selection.
(line 96)
* searching directory trees <3>: File and Directory Selection.
(line 101)
* searching directory trees <4>: File and Directory Selection.
(line 109)
* searching for a pattern: Introduction. (line 6)
* sl GREP_COLORS capability: Environment Variables.
(line 77)
* space character class: Character Classes and Bracket Expressions.
(line 65)
* space characters: Character Classes and Bracket Expressions.
(line 65)
* subexpression: Back-references and Subexpressions.
(line 6)
* suppress binary data: File and Directory Selection.
(line 8)
* suppress error messages: General Output Control.
(line 87)
* symbolic links: File and Directory Selection.
(line 62)
* symbolic links <1>: File and Directory Selection.
(line 101)
* symbolic links <2>: File and Directory Selection.
(line 109)
* tab-aligned content lines: Output Line Prefix Control.
(line 41)
* translation of message language: Environment Variables.
(line 179)
* upper character class: Character Classes and Bracket Expressions.
(line 70)
* upper-case letters: Character Classes and Bracket Expressions.
(line 70)
* usage summary, printing: Generic Program Information.
(line 7)
* usage, examples: Usage. (line 6)
* using grep, Q&A: Usage. (line 17)
* variants of grep: grep Programs. (line 6)
* version, printing: Generic Program Information.
(line 12)
* whitespace characters: Character Classes and Bracket Expressions.
(line 65)
* with filename prefix: Output Line Prefix Control.
(line 18)
* xdigit character class: Character Classes and Bracket Expressions.
(line 74)
* xdigit class: Character Classes and Bracket Expressions.
(line 74)
* zero-terminated file names: Output Line Prefix Control.
(line 50)
* zero-terminated lines: Other Options. (line 33)
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