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Virgin import of a trimmed down GNU Grep 2.3.

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\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename grep.info
@settitle grep, print lines matching a pattern
@c %**end of header
@c This file has the new style title page commands.
@c Run `makeinfo' rather than `texinfo-format-buffer'.
@c smallbook
@c tex
@c \overfullrule=0pt
@c end tex
@include version.texi
@c Combine indices.
@syncodeindex ky cp
@syncodeindex pg cp
@syncodeindex tp cp
@defcodeindex op
@syncodeindex op fn
@ifinfo
@direntry
* grep: (grep). print lines matching a pattern.
@end direntry
This file documents @sc{grep}, a pattern matching engine.
Published by the Free Software Foundation,
59 Temple Place - Suite 330
Boston, MA 02111-1307, USA
Copyright (C) 1998 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.
@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.
Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end ifinfo
@setchapternewpage off
@titlepage
@title grep, searching for a pattern
@subtitle version @value{VERSION}, @value{UPDATED}
@author Alain Magloire et al.
@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1998 Free Software Foundation, Inc.
@sp 2
Published by the Free Software Foundation, @*
59 Temple Place - Suite 330, @*
Boston, MA 02111-1307, USA
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 and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.
Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.
@end titlepage
@page
@node Top, Introduction, (dir), (dir)
@comment node-name, next, previous, up
@ifinfo
This document was produced for version @value{VERSION} of @sc{GNU} @sc{grep}.
@end ifinfo
@menu
* Introduction:: Introduction.
* Invoking:: Invoking @sc{grep}; description of options.
* Diagnostics:: Exit status returned by @sc{grep}.
* Grep Programs:: @sc{grep} programs.
* Regular Expressions:: Regular Expressions.
* Reporting Bugs:: Reporting Bugs.
* Concept Index:: A menu with all the topics in this manual.
* Index:: A menu with all @sc{grep} commands
and command-line options.
@end menu
@node Introduction, Invoking, Top, Top
@comment node-name, next, previous, up
@chapter Introduction
@cindex Searching for a pattern.
@sc{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. @sc{grep} expects to do the matching on text.
Since newline is also a separator for the list of patterns, there
is no way to match newline characters in a text.
@node Invoking, Diagnostics, Introduction, Top
@comment node-name, next, previous, up
@chapter Invoking @sc{grep}
@sc{grep} comes with a rich set of options from POSIX.2 and GNU extensions.
@table @samp
@item -c
@itemx --count
@opindex -c
@opindex -count
@cindex counting lines
Suppress normal output; instead print a count of matching
lines for each input file. With the @samp{-v}, @samp{--revert-match} option,
count non-matching lines.
@item -e @var{pattern}
@itemx --regexp=@var{pattern}
@opindex -e
@opindex --regexp=@var{pattern}
@cindex pattern list
Use @var{pattern} as the pattern; useful to protect patterns
beginning with a @samp{-}.
@item -f @var{file}
@itemx --file=@var{file}
@opindex -f
@opindex --file
@cindex pattern from file
Obtain patterns from @var{file}, one per line. The empty
file contains zero patterns, and therefore matches nothing.
@item -i
@itemx --ignore-case
@opindex -i
@opindex --ignore-case
@cindex case insensitive search
Ignore case distinctions in both the pattern and the input files.
@item -l
@itemx --files-with-matches
@opindex -l
@opindex --files-with-matches
@cindex names of matching files
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.
@item -n
@itemx --line-number
@opindex -n
@opindex --line-number
@cindex line numbering
Prefix each line of output with the line number within its input file.
@item -q
@itemx --quiet
@itemx --silent
@opindex -q
@opindex --quiet
@opindex --silent
@cindex quiet, silent
Quiet; suppress normal output. The scanning of every file will stop on
the first match. Also see the @samp{-s} or @samp{--no-messages} option.
@item -s
@itemx --no-messages
@opindex -s
@opindex --no-messages
@cindex suppress error messages
Suppress error messages about nonexistent or unreadable files.
Portability note: unlike GNU @sc{grep}, BSD @sc{grep} does not comply
with POSIX.2, because BSD @sc{grep} lacks a @samp{-q} option and its
@samp{-s} option behaves like GNU @sc{grep}'s @samp{-q} option. Shell
scripts intended to be portable to BSD @sc{grep} should avoid both
@samp{-q} and @samp{-s} and should redirect
output to @file{/dev/null} instead.
@item -v
@itemx --revert-match
@opindex -v
@opindex --revert-match
@cindex revert matching
@cindex print non-matching lines
Invert the sense of matching, to select non-matching lines.
@item -x
@itemx --line-regexp
@opindex -x
@opindex --line-regexp
@cindex match the whole line
Select only those matches that exactly match the whole line.
@end table
@section GNU Extensions
@table @samp
@item -A @var{num}
@itemx --after-context=@var{num}
@opindex -A
@opindex --after-context
@cindex after context
@cindex context lines, after match
Print @var{num} lines of trailing context after matching lines.
@item -B @var{num}
@itemx --before-context=@var{num}
@opindex -B
@opindex --before-context
@cindex before context
@cindex context lines, before match
Print @var{num} lines of leading context before matching lines.
@item -C
@itemx --context@var{[=num]}
@opindex -C
@opindex --context
@cindex context
Print @var{num} lines (default 2) of output context.
@item -NUM
@opindex -NUM
Same as @samp{--context=@var{num}} lines of leading and trailing
context. However, grep will never print any given line more than once.
@item -V
@itemx --version
@opindex -V
@opindex --version
@cindex Version, printing
Print the version number of @sc{grep} to the standard output stream.
This version number should be included in all bug reports.
@item --help
@opindex --help
@cindex Usage summary, printing
Print a usage message briefly summarizing these command-line options
and the bug-reporting address, then exit.
@item -b
@itemx --byte-offset
@opindex -b
@opindex --byte-offset
@cindex byte offset
Print the byte offset within the input file before each line of output.
When @sc{grep} runs on MS-DOS or MS-Windows, the printed byte offsets
depend on whether the @samp{-u} (@samp{--unix-byte-offsets}) option is
used; see below.
@item -d @var{action}
@itemx --directories=@var{action}
@opindex -d
@opindex --directories
@cindex directory search
If an input file is a directory, use @var{action} to process it.
By default, @var{action} is @samp{read}, which means that directories are
read just as if they were ordinary files (some operating systems
and filesystems disallow this, and will cause @sc{grep} to print error
messages for every directory). If @var{action} is @samp{skip},
directories are silently skipped. If @var{action} is @samp{recurse},
@sc{grep} reads all files under each directory, recursively; this is
equivalent to the @samp{-r} option.
@item -h
@itemx --no-filename
@opindex -h
@opindex --no-filename
@cindex no filename prefix
Suppress the prefixing of filenames on output when multiple files are searched.
@item -L
@itemx --files-without-match
@opindex -L
@opindex --files-without-match
@cindex files which don't 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.
@item -a
@itemx --text
@opindex -a
@opindex --text
@cindex suppress binary data
@cindex binary files
Do not suppress output lines that contain binary data.
Normally, if the first few bytes of a file indicate
that the file contains binary data, grep outputs only a
message saying that the file matches the pattern. This
option causes grep to act as if the file is a text
file, even if it would otherwise be treated as binary.
@emph{Warning:} the result might be binary garbage
printed to the terminal, which can have nasty
side-effects if the terminal driver interprets some of
it as commands.
@item -w
@itemx --word-regexp
@opindex -w
@opindex --word-regexp
@cindex matching whole words
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.
@item -r
@itemx --recursive
@opindex -r
@opindex --recursive
@cindex recursive search
@cindex searching directory trees
For each directory mentioned in the command line, read and process all
files in that directory, recursively. This is the same as the @samp{-d
recurse} option.
@item -y
@opindex -y
@cindex case insensitive search, obsolete option
Obsolete synonym for @samp{-i}.
@item -U
@itemx --binary
@opindex -U
@opindex --binary
@cindex DOS/Windows binary files
@cindex binary files, DOS/Windows
Treat the file(s) as binary. By default, under MS-DOS
and MS-Windows, @sc{grep} guesses the file type by looking
at the contents of the first 32KB read from the file.
If @sc{grep} decides the file is a text file, it strips the
CR characters from the original file contents (to make
regular expressions with @code{^} and @code{$} work correctly).
Specifying @samp{-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 is only supported on
MS-DOS and MS-Windows.
@item -u
@itemx --unix-byte-offsets
@opindex -u
@opindex --unix-byte-offsets
@cindex DOS byte offsets
@cindex byte offsets, on DOS/Windows
Report Unix-style byte offsets. This switch causes
@sc{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 off. This will produce results identical to running @sc{grep} on
a Unix machine. This option has no effect unless @samp{-b}
option is also used; it is only supported on MS-DOS and
MS-Windows.
@end table
Several additional options control which variant of the @sc{grep}
matching engine is used. @xref{Grep Programs}.
@sc{grep} uses the environment variable @var{LANG} to
provide internationalization support, if compiled with this feature.
@node Diagnostics, Grep Programs, Invoking, Top
@comment node-name, next, previous, up
@chapter Diagnostics
Normally, exit status is 0 if matches were found, and 1 if no matches
were found (the @samp{-v} option inverts the sense of the exit status).
Exit status is 2 if there were syntax errors in the pattern,
inaccessible input files, or other system errors.
@node Grep Programs, Regular Expressions, Diagnostics, Top
@comment node-name, next, previous, up
@chapter @sc{grep} programs
@sc{grep} searches the named input files (or standard input if no
files are named, or the file name @file{-} is given) for lines containing
a match to the given pattern. By default, @sc{grep} prints the matching lines.
There are three major variants of @sc{grep}, controlled by the following options.
@table @samp
@item -G
@itemx --basic-regexp
@opindex -G
@opindex --basic-regexp
@cindex matching basic regular expressions
Interpret pattern as a basic regular expression. This is the default.
@item -E
@item --extended-regexp
@opindex -E
@opindex --extended-regexp
@cindex matching extended regular expressions
Interpret pattern as an extended regular expression.
@item -F
@itemx --fixed-strings
@opindex -F
@opindex --fixed-strings
@cindex matching fixed strings
Interpret pattern as a list of fixed strings, separated
by newlines, any of which is to be matched.
@end table
In addition, two variant programs @sc{egrep} and @sc{fgrep} are available.
@sc{egrep} is similar (but not identical) to @samp{grep -E}, and
is compatible with the historical Unix @sc{egrep}. @sc{fgrep} is the
same as @samp{grep -F}.
@node Regular Expressions, Reporting Bugs, Grep Programs, Top
@comment node-name, next, previous, up
@chapter Regular Expressions
@cindex regular expressions
A @dfn{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.
@sc{grep} understands two different versions of regular expression
syntax: ``basic'' and ``extended''. In GNU @sc{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 list of characters enclosed by @samp{[} and @samp{]} matches any
single character in that list; if the first character of the list is the
caret @samp{^}, then it
matches any character @strong{not} in the list. For example, the regular
expression @samp{[0123456789]} matches any single digit.
A range of @sc{ascii} characters may be specified by giving the first
and last characters, separated by a hyphen. Finally, certain named
classes of characters are predefined. Their names are self explanatory,
and they are :
@cindex classes of characters
@cindex character classes
@table @samp
@item [:alnum:]
@opindex alnum
@cindex alphanumeric characters
Any of [:digit:] or [:alpha:]
@item [:alpha:]
@opindex alpha
@cindex alphabetic characters
Any local-specific or one of the @sc{ascii} letters:@*
@code{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},@*
@code{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}.
@item [:cntrl:]
@opindex cntrl
@cindex control characters
Any of @code{BEL}, @code{BS}, @code{CR}, @code{FF}, @code{HT},
@code{NL}, or @code{VT}.
@item [:digit:]
@opindex digit
@cindex digit characters
@cindex numeric characters
Any one of @code{0 1 2 3 4 5 6 7 8 9}.
@item [:graph:]
@opindex graph
@cindex graphic characters
Anything that is not a @samp{[:alphanum:]} or @samp{[:punct:]}.
@item [:lower:]
@opindex lower
@cindex lower-case alphabetic characters
Any one of @code{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}.
@item [:print:]
@opindex print
@cindex printable characters
Any character from the @samp{[:space:]} class, and any character that is
@strong{not} in the @samp{[:isgraph:]} class.
@item [:punct:]
@opindex punct
@cindex punctuation characters
Any one of @code{!@: " #% & ' ( ) ; < = > ?@: [ \ ] * + , - .@: / : ^ _ @{ | @}}.
@item [:space:]
@opindex space
@cindex space characters
@cindex whitespace characters
Any one of @code{CR FF HT NL VT SPACE}.
@item [:upper:]
@opindex upper
@cindex upper-case alphabetic characters
Any one of @code{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}.
@item [:xdigit:]
@opindex xdigit
@cindex xdigit class
@cindex hexadecimal digits
Any one of @code{a b c d e f A B C D E F 0 1 2 3 4 5 6 7 8 9}.
@end table
For example, @samp{[[:alnum:]]} means @samp{[0-9A-Za-z]}, except the latter
form is dependent upon the @sc{ascii} character encoding, whereas the
former is portable. (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. To include a literal @samp{]}, place it
first in the list. Similarly, to include a literal @samp{^}, place it anywhere
but first. Finally, to include a literal @samp{-}, place it last.
The period @samp{.} matches any single character. The symbol @samp{\w}
is a synonym for @samp{[[:alnum:]]} and @samp{\W} is a synonym for
@samp{[^[:alnum]]}.
The caret @samp{^} and the dollar sign @samp{$} are metacharacters that
respectively match the empty string at the beginning and end
of a line. The symbols @samp{\<} and @samp{\>} respectively match the
empty string at the beginning and end of a word. The symbol
@samp{\b} matches the empty string at the edge of a word, and @samp{\B}
matches the empty string provided it's not at the edge of a word.
A regular expression may be followed by one of several
repetition operators:
@table @samp
@item ?
@opindex ?
@cindex question mark
@cindex match sub-expression at most once
The preceding item is optional and will be matched at most once.
@item *
@opindex *
@cindex asterisk
@cindex match sub-expression zero or more times
The preceding item will be matched zero or more times.
@item +
@opindex +
@cindex plus sign
The preceding item will be matched one or more times.
@item @{@var{n}@}
@opindex @{n@}
@cindex braces, one argument
@cindex match sub-expression n times
The preceding item is matched exactly @var{n} times.
@item @{@var{n},@}
@opindex @{n,@}
@cindex braces, second argument omitted
@cindex match sub-expression n or more times
The preceding item is matched n or more times.
@item @{,@var{m}@}
@opindex @{,m@}
@cindex braces, first argument omitted
@cindex match sub-expression at most m times
The preceding item is optional and is matched at most @var{m} times.
@item @{@var{n},@var{m}@}
@opindex @{n,m@}
@cindex braces, two arguments
The preceding item is matched at least @var{n} times, but not more than
@var{m} times.
@end table
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 @samp{|}; 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.
The backreference @samp{\@var{n}}, where @var{n} is a single digit, matches the
substring previously matched by the @var{n}th parenthesized subexpression
of the regular expression.
@cindex basic regular expressions
In basic regular expressions the metacharacters @samp{?}, @samp{+},
@samp{@{}, @samp{|}, @samp{(}, and @samp{)} lose their special meaning;
instead use the backslashed versions @samp{\?}, @samp{\+}, @samp{\@{},
@samp{\|}, @samp{\(}, and @samp{\)}.
In @sc{egrep} the metacharacter @samp{@{} loses its special meaning;
instead use @samp{\@{}. This not true for @samp{grep -E}.
@node Reporting Bugs, Concept Index, Regular Expressions, Top
@comment node-name, next, previous, up
@chapter Reporting bugs
@cindex Bugs, reporting
Email bug reports to @email{bug-gnu-utils@@gnu.org}.
Be sure to include the word ``grep'' somewhere in the ``Subject:'' field.
Large repetition counts in the @samp{@{m,n@}} construct may cause
@sc{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.
Backreferences are very slow, and may require exponential time.
@page
@node Concept Index , Index, Reporting Bugs, Top
@comment node-name, next, previous, up
@unnumbered Concept Index
This is a general index of all issues discussed in this manual, with the
exception of the @sc{grep} commands and command-line options.
@printindex cp
@page
@node Index, , Concept Index, Top
@unnumbered Index
This is an alphabetical list of all @sc{grep} commands and command-line
options.
@printindex fn
@contents
@bye

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@set UPDATED 10 February 1999
@set EDITION 2.3
@set VERSION 2.3