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GREP(1)								       GREP(1)

NAME
       grep,  egrep,  fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep -
       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.	 zegrep is the same as grep -EZ.  zfgrep is  the  same
       as grep -FZ.

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
	      Interpret	 PATTERN as a Perl regular expression.	This option is
	      not supported in FreeBSD.

       -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-buffered
	      Flush output on every line.  Note that this incurs a performance
	      penalty.

       -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.

       --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.

       -J, --bz2decompress
	      Decompress the bzip2(1) compressed input data before searching.

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:],  [:blank:],	[: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”.

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)
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