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GREP(1)			    General Commands Manual		       GREP(1)

NAME
       grep, egrep, fgrep - 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.

OPTIONS
       -A NUM, --after-context=NUM
	      Print NUM	 lines	of  trailing  context  after  matching	lines.
	      Places  a	 line  containing  --  between	contiguous  groups  of
	      matches.

       -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.
	      Places  a	 line  containing  --  between	contiguous  groups  of
	      matches.

       -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  bi-
	      nary  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 --bi-
	      nary-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 NUM, --context=NUM
	      Print NUM	lines of output	context.  Places a line	containing  --
	      between contiguous groups	of matches.

       -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.

       --colour[=WHEN],	--color[=WHEN]
	      Surround	the matching string with the marker find in GREP_COLOR
	      environment variable. WHEN may be	`never', `always', or `auto'

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

       -d ACTION, --directories=ACTION
	      If  an  input file is a directory, use ACTION to process it.  By
	      default, ACTION is read, which means that	directories  are  read
	      just  as if they were ordinary files.  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 -.  May be specified	more than once.

       -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 therefore 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.

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

       --line-buffered
	      Use line buffering, it can be a performance penalty.

       -m NUM, --max-count=NUM
	      Stop  reading  a file after NUM matching lines.  If the input is
	      standard input from a regular file, and NUM matching  lines  are
	      output,  grep  ensures  that the standard	input is positioned to
	      just after the last matching line	before exiting,	regardless  of
	      the  presence of trailing	context	lines.	This enables a calling
	      process to resume	a search.  When	grep stops after NUM  matching
	      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.

       --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.

       -o, --only-matching
	      Show only	the part of a matching line that matches PATTERN.

       -q, --quiet, --silent
	      Quiet;  do  not write anything to	standard output.  Exit immedi-
	      ately with zero status if	any match is found, even if  an	 error
	      was detected.  Also see the -s or	--no-messages option.

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

	 --include=PATTERN
	      Recurse in directories only searching file matching PATTERN.

	 --exclude=PATTERN
	      Recurse in directories skip file matching	PATTERN.

       -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 re-
	      port 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.

       -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.

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, ba-
       sic 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  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 charac-
       ters separated by a hyphen.  It matches any single character that sorts
       between the two characters, inclusive, using the	locale's collating se-
       quence and character set.  For example, in the default C	locale,	 [a-d]
       is  equivalent  to  [abcd].  Many locales sort characters in dictionary
       order, and in these  locales  [a-d]  is	typically  not	equivalent  to
       [abcd];	it  might  be equivalent to [aBbCcDd], for example.  To	obtain
       the traditional interpretation of bracket expressions, you can use  the
       C locale	by setting the LC_ALL environment variable to the value	C.

       Finally,	 certain  named	 classes  of  characters are predefined	within
       bracket expressions, as follows.	 Their 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 de-
       pends upon the C	locale and the ASCII character encoding,  whereas  the
       former  is  independent	of  locale  and	character set.	(Note that the
       brackets	in these class names are part of the symbolic names, and  must
       be  included  in	addition to the	brackets delimiting the	bracket	list.)
       Most metacharacters lose	their special meaning inside  lists.   To  in-
       clude  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 ex-
       pression	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 re-
       sulting 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's behavior is affected by the following environment	variables.

       A locale	LC_foo is specified by examining the three  environment	 vari-
       ables  LC_ALL,  LC_foo,	LANG, in that order.  The first	of these vari-
       ables that is set specifies the locale.	For example, if	LC_ALL is  not
       set, but	LC_MESSAGES is set to pt_BR, then Brazilian Portuguese is used
       for the LC_MESSAGES locale.  The	C locale is used if none of these  en-
       vironment variables are set, or if the locale catalog is	not installed,
       or if grep was not compiled with	national language support (NLS).

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

       GREP_COLOR
	      Specifies	the marker for highlighting.

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

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

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

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

       _N_GNU_nonoption_argv_flags_
	      (Here N is grep's	numeric	process	ID.)  If the ith character  of
	      this  environment	variable's value is 1, do not consider the ith
	      operand of grep to be an option, even if it appears to  be  one.
	      A	 shell	can put	this variable in the environment for each com-
	      mand 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  li-
	      brary, and only when POSIXLY_CORRECT is not set.

DIAGNOSTICS
       Normally, exit status is	0 if selected lines are	found and 1 otherwise.
       But the exit status is 2	if an error occurred, unless the -q or --quiet
       or --silent option is used and a	selected line is found.

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

       Large repetition	counts in the {n,m} construct may cause	 grep  to  use
       lots of memory.	In addition, certain other obscure regular expressions
       require exponential time	and space, and may cause grep to  run  out  of
       memory.

       Backreferences are very slow, and may require exponential time.

GNU Project			 June 16, 2003			       GREP(1)

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

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