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GREP(1)								       GREP(1)

NAME
       grep, egrep, fgrep, zgrep - print lines matching	a pattern

SYNOPSIS
       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]

DESCRIPTION
       grep  searches the named	input FILEs (or	standard input if no files are
       named, or the file name - is given) for lines containing	a match	to the
       given PATTERN.  By default, grep	prints the matching lines.

       In addition, two	variant	programs egrep and fgrep are available.	 egrep
       is the same as grep -E.	fgrep is the same as grep -F.	zgrep  is  the
       same as grep -Z.

OPTIONS
       -A NUM, --after-context=NUM
	      Print NUM	lines of trailing context after	matching lines.

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

       -B NUM, --before-context=NUM
	      Print NUM	lines of leading context before	matching lines.

       -C [NUM], -NUM, --context[=NUM]
	      Print NUM	lines (default 2) of output context.

       -b, --byte-offset
	      Print the	byte offset within the input file before each line  of
	      output.

       --binary-files=TYPE
	      If the first few bytes of	a file indicate	that the file contains
	      binary data, assume that the file	is of type TYPE.  By  default,
	      TYPE is binary, and grep normally	outputs	either a one-line mes-
	      sage saying that a binary	file matches, or no message  if	 there
	      is  no  match.   If  TYPE	 is without-match, grep	assumes	that a
	      binary file does not match; this is equivalent to	the -I option.
	      If  TYPE	is  text,  grep	 processes a binary file as if it were
	      text; this is  equivalent	 to  the  -a  option.	Warning:  grep
	      --binary-files=text  might output	binary garbage,	which can have
	      nasty side effects if the	output is a terminal and if the	termi-
	      nal driver interprets some of it as commands.

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

       -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.  If	ACTION is skip,	direc-
	      tories are silently skipped.  If ACTION is recurse,  grep	 reads
	      all  files under each directory, recursively; this is equivalent
	      to the -r	option.

       -E, --extended-regexp
	      Interpret	PATTERN	as an extended regular expression (see below).

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

       -F, --fixed-strings
	      Interpret	PATTERN	as a list of fixed strings, separated by  new-
	      lines, any of which is to	be matched.

       -f FILE,	--file=FILE
	      Obtain  patterns	from  FILE, one	per line.  The empty file con-
	      tains zero patterns, and therfore	matches	nothing.

       -G, --basic-regexp
	      Interpret	PATTERN	as a basic  regular  expression	 (see  below).
	      This is the default.

       -H, --with-filename
	      Print the	filename for each match.

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

       --help Output a brief help message.

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

       -i, --ignore-case
	      Ignore  case  distinctions  in  both  the	 PATTERN and the input
	      files.

       -L, --files-without-match
	      Suppress normal output; instead print the	 name  of  each	 input
	      file from	which no output	would normally have been printed.  The
	      scanning will stop on the	first match.

       -l, --files-with-matches
	      Suppress normal output; instead print the	 name  of  each	 input
	      file  from  which	 output	would normally have been printed.  The
	      scanning will stop on the	first match.

       --mmap If possible, use the mmap(2) system call to read input,  instead
	      of  the default read(2) system call.  In some situations,	--mmap
	      yields better performance.  However, --mmap can cause  undefined
	      behavior	(including  core dumps)	if an input file shrinks while
	      grep is operating, or if an I/O error occurs.

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

       -q, --quiet, --silent
	      Quiet;  suppress	normal	output.	 The scanning will stop	on the
	      first match.  Also see the -s or --no-messages option below.

       -r, --recursive
	      Read all files under each	directory, recursively;	this is	equiv-
	      alent to the -d recurse option.

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

       -U, --binary
	      Treat the	file(s)	as binary.  By default,	under MS-DOS  and  MS-
	      Windows,	grep  guesses the file type by looking at the contents
	      of the first 32KB	read from the file.  If	grep decides the  file
	      is  a  text  file, it strips the CR characters from the original
	      file contents (to	make regular expressions with  ^  and  $  work
	      correctly).  Specifying -U overrules this	guesswork, causing all
	      files to be read and passed to the matching mechanism  verbatim;
	      if  the  file is a text file with	CR/LF pairs at the end of each
	      line, this will cause some regular expressions  to  fail.	  This
	      option  has no effect on platforms other than MS-DOS and MS-Win-
	      dows.

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

       -V, --version
	      Print  the  version number of grep to standard error.  This ver-
	      sion number should be included in	all bug	reports	(see below).

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

       -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  con-
	      stituent	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.

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

       -y     Obsolete synonym for -i.

       --null Output a zero byte (the ASCII  NUL  character)  instead  of  the
	      character	 that normally follows a file name.  For example, grep
	      -l --null	outputs	a zero byte after each file  name  instead  of
	      the  usual  newline.   This option makes the output unambiguous,
	      even in the presence of file names containing unusual characters
	      like  newlines.  This option can be used with commands like find
	      -print0, perl -0,	sort -z, and xargs  -0	to  process  arbitrary
	      file names, even those that contain newline characters.

       -Z, --decompress
	      Decompress the input data	before searching.  This	option is only
	      available	if compiled with zlib(3) library.

REGULAR	EXPRESSIONS
       A regular expression is a pattern that  describes  a  set  of  strings.
       Regular	expressions  are constructed analogously to arithmetic expres-
       sions, by using various operators to combine smaller expressions.

       grep understands	two different versions of regular  expression  syntax:
       "basic"	and "extended."	 In GNU	grep, there is no difference in	avail-
       able 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	[ and ]	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.  A range of charac-
       ters may	be specified by	giving the first and  last  characters,	 sepa-
       rated  by  a  hyphen.  Finally, certain named classes of	characters are
       predefined.  Their names	are self explanatory, and they are  [:alnum:],
       [:alpha:],   [:cntrl:],	[:digit:],  [:graph:],	[:lower:],  [:print:],
       [:punct:],  [:space:],  [:upper:],  and	 [:xdigit:].	For   example,
       [[:alnum:]]  means [0-9A-Za-z], except the latter form depends upon the
       POSIX locale and	the ASCII character encoding, whereas  the  former  is
       independent  of	locale	and character set.  (Note that the brackets in
       these class names are part of the symbolic names, and must be  included
       in  addition  to	 the  brackets	delimiting  the	 bracket  list.)  Most
       metacharacters lose their special meaning inside	lists.	To  include  a
       literal	] place	it first in the	list.  Similarly, to include a literal
       ^ place it anywhere but first.  Finally,	to include a literal  -	 place
       it last.

       The period .  matches any single	character.  The	symbol \w is a synonym
       for [[:alnum:]] and \W is a synonym for [^[:alnum]].

       The caret ^ and the dollar sign $ are metacharacters that  respectively
       match the empty string at the beginning and end of a line.  The symbols
       \< and \> respectively match the	empty string at	the beginning and  end
       of  a  word.   The  symbol \b matches the empty string at the edge of a
       word, and \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 oper-
       ators:
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or	more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {n,m}  The preceding item is matched at least n	times,	but  not  more
	      than m times.

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

       Two  regular  expressions  may  be  joined by the infix operator	|; the
       resulting regular expression matches any	string matching	either	subex-
       pression.

       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 \n, where n is a single digit, matches the substring
       previously matched by the nth parenthesized subexpression of the	 regu-
       lar expression.

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

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

       GNU  egrep  attempts to support traditional usage by assuming that { is
       not special if it would be the start of an invalid interval  specifica-
       tion.   For example, the	shell command egrep '{1' searches for the two-
       character string	{1 instead of reporting	a syntax error in the  regular
       expression.  POSIX.2 allows this	behavior as an extension, but portable
       scripts should avoid it.

ENVIRONMENT VARIABLES
       GREP_OPTIONS
	      This variable specifies default options to be placed in front of
	      any   explicit   options.	   For	example,  if  GREP_OPTIONS  is
	      '--binary-files=without-match --directories=skip', grep  behaves
	      as  if the two options --binary-files=without-match and --direc-
	      tories=skip had been  specified  before  any  explicit  options.
	      Option  specifications are separated by whitespace.  A backslash
	      escapes the next character, so it	can  be	 used  to  specify  an
	      option containing	whitespace or a	backslash.

       LC_ALL, LC_MESSAGES, LANG
	      These variables specify the LC_MESSAGES locale, which determines
	      the language that	grep uses for messages.	 The locale is	deter-
	      mined  by	 the  first  of	these variables	that is	set.  American
	      English is used if none of these environment variables are  set,
	      or  if  the message catalog is not installed, or if grep was not
	      compiled with national language support (NLS).

       LC_ALL, LC_CTYPE, LANG
	      These variables specify the LC_CTYPE  locale,  which  determines
	      the  type	 of characters,	e.g., which characters are whitespace.
	      The locale is determined by the first of these variables that is
	      set.   The  POSIX	 locale	 is  used if none of these environment
	      variables	are set, or if the locale catalog is not installed, or
	      if grep was not compiled with national language support (NLS).

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

DIAGNOSTICS
       Normally, exit status is	0 if matches were found, and 1 if  no  matches
       were  found.   (The  -v	option	inverts	the sense of the exit status.)
       Exit status is 2	if there were syntax errors in the pattern, inaccessi-
       ble input files,	or other system	errors.

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

       Large repetition	counts in the {m,n} 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.

       Backreferences are very slow, and may require exponential time.

GNU Project			  2000/01/26			       GREP(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | ENVIRONMENT VARIABLES | DIAGNOSTICS | BUGS

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