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GREP(1)								       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.

       -C NUM, --context=NUM
	      Print  NUM lines of output context.  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
	      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.

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

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

       -F, --fixed-strings
	      Interpret	PATTERN	as a list of fixed strings, separated by  new-
	      lines,  any of which is to be matched.  -P, --perl-regexp	Inter-
	      pret PATTERN as a	Perl regular expression.

       -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.

       -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.

       --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-buffering
	      Use line buffering, it can be a performance penality.

       -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
	      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.

       -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,
       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 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
       sequence	 and  character	 set.	For  example, in the default C locale,
       [a-d] is	equivalent to [abcd].  Many locales sort characters in dictio-
       nary  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
       depends upon the	C locale and the ASCII character encoding, whereas the
       former is independent of	locale and  character  set.   (Note  that  the
       brackets	 in these class	names are part of the symbolic names, and must
       be included in addition to the brackets delimiting the  bracket	list.)
       Most  metacharacters  lose  their  special  meaning  inside  lists.  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'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
       environment variables  are  set,	 or  if	 the  locale  catalog  is  not
       installed,  or  if grep was not compiled	with national language support
       (NLS).

       GREP_OPTIONS
	      This variable specifies default options to be placed in front of
	      any   explicit   options.	   For	example,  if  GREP_OPTIONS  is
	      '--binary-files=without-match --directories=skip', grep  behaves
	      as  if the two options --binary-files=without-match and --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.

       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
	      behaves  more  like  other  GNU programs.	 POSIX.2 requires that
	      options that follow file names must be treated as	file names; by
	      default,	such  options are permuted to the front	of the operand
	      list and are treated as options.	Also,  POSIX.2	requires  that
	      unrecognized  options  be	diagnosed as "illegal",	but since they
	      are not really against the law the default is to	diagnose  them
	      as   "invalid".	POSIXLY_CORRECT	 also  disables	 _N_GNU_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
	      library, 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			  2002/01/22			       GREP(1)

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

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