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GREP(1)								       GREP(1)

NAME
       grep, egrep, fgrep, rgrep - 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 if a single hyphen-minus (-) is given as file name) for lines
       containing  a  match to the given PATTERN.  By default, grep prints the
       matching lines.

       In  addition,  three  variant  programs	egrep,	fgrep  and  rgrep  are
       available.   egrep  is  the  same  as  grep -E.	 fgrep	is the same as
       grep -F.	 rgrep is the same as grep -r.	Direct	invocation  as	either
       egrep  or  fgrep	 is  deprecated,  but  is provided to allow historical
       applications that rely on them to run unmodified.

OPTIONS
   Generic Program Information
       --help Print a usage message  briefly  summarizing  these  command-line
	      options and the bug-reporting address, then exit.

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

   Matcher Selection
       -E, --extended-regexp
	      Interpret	 PATTERN  as  an extended regular expression (ERE, see
	      below).  (-E is specified by POSIX.)

       -F, --fixed-strings
	      Interpret PATTERN as a  list  of	fixed  strings,	 separated  by
	      newlines,	 any  of  which is to be matched.  (-F is specified by
	      POSIX.)

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

       -P, --perl-regexp
	      Interpret	 PATTERN  as  a	 Perl  regular	expression  (PCRE, see
	      below).  This is highly experimental and grep  -P	 may  warn  of
	      unimplemented features.

   Matching Control
       -e PATTERN, --regexp=PATTERN
	      Use  PATTERN  as	the  pattern.	This  can  be  used to specify
	      multiple search patterns, or to protect a pattern beginning with
	      a hyphen (-).  (-e is specified by POSIX.)

       -f FILE, --file=FILE
	      Obtain  patterns	from  FILE,  one  per  line.   The  empty file
	      contains zero patterns, and therefore matches nothing.   (-f  is
	      specified by POSIX.)

       -i, --ignore-case
	      Ignore  case  distinctions  in  both  the	 PATTERN and the input
	      files.  (-i is specified by POSIX.)

       -v, --invert-match
	      Invert the sense of matching, to select non-matching lines.  (-v
	      is specified by POSIX.)

       -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
	      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.

       -x, --line-regexp
	      Select  only  those  matches  that exactly match the whole line.
	      (-x is specified by POSIX.)

       -y     Obsolete synonym for -i.

   General Output Control
       -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.	 (-c is specified by POSIX.)

       --color[=WHEN], --colour[=WHEN]
	      Surround	the  matched  (non-empty)  strings,  matching	lines,
	      context  lines,  file  names,  line  numbers,  byte offsets, and
	      separators (for fields and groups of context lines) with	escape
	      sequences	 to display them in color on the terminal.  The colors
	      are  defined  by	the  environment  variable  GREP_COLORS.   The
	      deprecated  environment  variable GREP_COLOR is still supported,
	      but its setting does not have priority.  WHEN is never,  always,
	      or auto.

       -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.  (-l is specified by
	      POSIX.)

       -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.

       -o, --only-matching
	      Print  only  the	matched	 (non-empty) parts of a matching line,
	      with each such part on a separate output line.

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

       -s, --no-messages
	      Suppress	error  messages about nonexistent or unreadable files.
	      Portability note: unlike GNU grep, 7th Edition Unix grep did not
	      conform to POSIX, because it lacked -q and its -s option behaved
	      like GNU grep's -q option.  USG-style grep also  lacked  -q  but
	      its  -s  option  behaved	like GNU grep.	Portable shell scripts
	      should avoid both -q and -s and  should  redirect	 standard  and
	      error output to /dev/null instead.  (-s is specified by POSIX.)

   Output Line Prefix Control
       -b, --byte-offset
	      Print  the 0-based byte offset within the input file before each
	      line of output.  If -o (--only-matching) is specified, print the
	      offset of the matching part itself.

       -H, --with-filename
	      Print  the  file	name for each match.  This is the default when
	      there is more than one file to search.

       -h, --no-filename
	      Suppress the prefixing of file names on  output.	 This  is  the
	      default  when there is only one file (or only standard input) to
	      search.

       --label=LABEL
	      Display input actually  coming  from  standard  input  as	 input
	      coming   from  file  LABEL.   This  is  especially  useful  when
	      implementing tools like zgrep, e.g.,  gzip  -cd  foo.gz  |  grep
	      --label=foo -H something.	 See also the -H option.

       -n, --line-number
	      Prefix  each  line of output with the 1-based line number within
	      its input file.  (-n is specified by POSIX.)

       -T, --initial-tab
	      Make sure that the first character of actual line	 content  lies
	      on a tab stop, so that the alignment of tabs looks normal.  This
	      is useful with options that prefix their output  to  the	actual
	      content:	-H,-n,	and  -b.   In order to improve the probability
	      that lines from a single file will all start at the same column,
	      this also causes the line number and byte offset (if present) to
	      be printed in a minimum size field width.

       -u, --unix-byte-offsets
	      Report Unix-style byte offsets.	This  switch  causes  grep  to
	      report  byte offsets as if the file were a 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 platforms other than MS-DOS and MS-Windows.

       -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.

   Context Line Control
       -A NUM, --after-context=NUM
	      Print NUM	 lines	of  trailing  context  after  matching	lines.
	      Places   a  line	containing  a  group  separator	 (--)  between
	      contiguous groups of matches.  With the  -o  or  --only-matching
	      option, this has no effect and a warning is given.

       -B NUM, --before-context=NUM
	      Print  NUM  lines	 of  leading  context  before  matching lines.
	      Places  a	 line  containing  a  group  separator	(--)   between
	      contiguous  groups  of  matches.	With the -o or --only-matching
	      option, this has no effect and a warning is given.

       -C NUM, -NUM, --context=NUM
	      Print NUM lines of output context.  Places a line	 containing  a
	      group separator (--) between contiguous groups of matches.  With
	      the -o or --only-matching option,	 this  has  no	effect	and  a
	      warning is given.

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

       --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
	      message  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
	      terminal driver interprets some of it as commands.

       -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, i.e., read directories just as if  they
	      were   ordinary	files.	 If  ACTION  is	 skip,	silently  skip
	      directories.  If ACTION is recurse, read all  files  under  each
	      directory,  recursively,	following  symbolic links only if they
	      are on the command line.	This is equivalent to the -r option.

       --exclude=GLOB
	      Skip  files  whose  base	name  matches  GLOB  (using   wildcard
	      matching).   A  file-name	 glob  can  use	 *,  ?,	 and [...]  as
	      wildcards, and \ to quote	 a  wildcard  or  backslash  character
	      literally.

       --exclude-from=FILE
	      Skip  files  whose  base name matches any of the file-name globs
	      read from FILE  (using  wildcard	matching  as  described	 under
	      --exclude).

       --exclude-dir=DIR
	      Exclude  directories  matching  the  pattern  DIR from recursive
	      searches.

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

       --include=GLOB
	      Search  only  files whose base name matches GLOB (using wildcard
	      matching as described under --exclude).

       -r, --recursive
	      Read all files  under  each  directory,  recursively,  following
	      symbolic	links  only  if they are on the command line.  This is
	      equivalent to the -d recurse option.

       -R, --dereference-recursive
	      Read all files under each directory,  recursively.   Follow  all
	      symbolic links, unlike -r.

   Other Options
       --line-buffered
	      Use  line	 buffering  on	output.	  This can cause a performance
	      penalty.

       --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.

       -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-
	      Windows.

       -z, --null-data
	      Treat the input as a set of lines, each  terminated  by  a  zero
	      byte  (the  ASCII NUL character) instead of a newline.  Like the
	      -Z or --null option, this option can be used with commands  like
	      sort -z to process arbitrary file names.

REGULAR EXPRESSIONS
       A  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.

       grep understands three different versions of regular expression syntax:
       “basic” (BRE), “extended” (ERE) and “perl” (PRCE). In  GNU grep,	 there
       is  no difference in available functionality between basic and extended
       syntaxes.  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.   Perl  regular  expressions give additional functionality,
       and are documented in pcresyntax(3) and pcrepattern(3), but  only  work
       if pcre is available in the system.

       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 meta-character with
       special meaning may be quoted by preceding it with a backslash.

       The period . matches any single character.

   Character Classes and Bracket Expressions
       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
       characters 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
       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  the  character  class of numbers and
       letters in the current locale. In the C locale and ASCII character  set
       encoding,  this is the same as [0-9A-Za-z].  (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 expression.)  Most
       meta-characters lose their special meaning inside bracket  expressions.
       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.

   Anchoring
       The caret ^ and the dollar sign $ are meta-characters that respectively
       match the empty string at the beginning and end of a line.

   The Backslash Character and Special Expressions
       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.  The symbol \w is a synonym for [_[:alnum:]] and
       \W is a synonym for [^_[:alnum:]].

   Repetition
       A regular expression may be  followed  by  one  of  several  repetition
       operators:
       ?      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.
       {,m}   The  preceding  item  is matched at most m times.	 This is a GNU
	      extension.
       {n,m}  The preceding item is matched at least n	times,	but  not  more
	      than m times.

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

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

   Precedence
       Repetition  takes  precedence  over  concatenation, which in turn takes
       precedence over alternation.  A whole expression	 may  be  enclosed  in
       parentheses   to	  override   these   precedence	  rules	  and  form  a
       subexpression.

   Back References and Subexpressions
       The back-reference \n, where n is a single digit, matches the substring
       previously  matched  by	the  nth  parenthesized	 subexpression	of the
       regular expression.

   Basic vs Extended Regular Expressions
       In basic regular expressions the meta-characters ?, +, {, |, (,	and  )
       lose  their  special  meaning; instead use the backslashed versions \?,
       \+, \{, \|, \(, and \).

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

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

ENVIRONMENT VARIABLES
       The   behavior  of  grep	 is  affected  by  the	following  environment
       variables.

       The locale for category LC_foo is  specified  by	 examining  the	 three
       environment  variables  LC_ALL, LC_foo, LANG, in that order.  The first
       of these variables that is set specifies the locale.  For  example,  if
       LC_ALL  is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
       Portuguese locale is used for the LC_MESSAGES category.	The  C	locale
       is  used	 if none of these environment variables are set, 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
	      --directories=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
	      This variable specifies the  color  used	to  highlight  matched
	      (non-empty) text.	 It is deprecated in favor of GREP_COLORS, but
	      still supported.	The mt, ms, and mc capabilities of GREP_COLORS
	      have  priority  over  it.	 It can only specify the color used to
	      highlight the matching non-empty text in any  matching  line  (a
	      selected	line  when the -v command-line option is omitted, or a
	      context line when -v is specified).  The default is 01;31, which
	      means  a	bold  red  foreground  text  on the terminal's default
	      background.

       GREP_COLORS
	      Specifies the colors and	other  attributes  used	 to  highlight
	      various  parts  of  the  output.	Its value is a colon-separated
	      list	of	capabilities	  that	     defaults	    to
	      ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36	 with  the  rv
	      and ne boolean capabilities omitted  (i.e.,  false).   Supported
	      capabilities are as follows.

	      sl=    SGR  substring  for  whole selected lines (i.e., matching
		     lines when the -v command-line option is omitted, or non-
		     matching  lines  when  -v	is specified).	If however the
		     boolean rv capability and the -v command-line option  are
		     both  specified,  it  applies  to	context matching lines
		     instead.  The default  is	empty  (i.e.,  the  terminal's
		     default color pair).

	      cx=    SGR substring for whole context lines (i.e., non-matching
		     lines when the -v	command-line  option  is  omitted,  or
		     matching  lines  when  -v	is specified).	If however the
		     boolean rv capability and the -v command-line option  are
		     both specified, it applies to selected non-matching lines
		     instead.  The default  is	empty  (i.e.,  the  terminal's
		     default color pair).

	      rv     Boolean  value  that reverses (swaps) the meanings of the
		     sl= and cx= capabilities when the -v command-line	option
		     is specified.  The default is false (i.e., the capability
		     is omitted).

	      mt=01;31
		     SGR substring for matching non-empty text in any matching
		     line  (i.e.,  a  selected	line  when the -v command-line
		     option  is	 omitted,  or  a  context  line	 when  -v   is
		     specified).   Setting  this is equivalent to setting both
		     ms= and mc= at once to the same value.  The default is  a
		     bold   red	  text	 foreground   over  the	 current  line
		     background.

	      ms=01;31
		     SGR substring for matching non-empty text in  a  selected
		     line.  (This is only used when the -v command-line option
		     is omitted.)  The effect  of  the	sl=  (or  cx=  if  rv)
		     capability	 remains  active  when	this  kicks  in.   The
		     default is a bold red text foreground  over  the  current
		     line background.

	      mc=01;31
		     SGR  substring  for  matching non-empty text in a context
		     line.  (This is only used when the -v command-line option
		     is	 specified.)   The  effect  of	the cx= (or sl= if rv)
		     capability	 remains  active  when	this  kicks  in.   The
		     default  is  a  bold red text foreground over the current
		     line background.

	      fn=35  SGR substring for file names prefixing any content	 line.
		     The  default  is  a  magenta  text	 foreground  over  the
		     terminal's default background.

	      ln=32  SGR substring for	line  numbers  prefixing  any  content
		     line.   The  default  is a green text foreground over the
		     terminal's default background.

	      bn=32  SGR substring for	byte  offsets  prefixing  any  content
		     line.   The  default  is a green text foreground over the
		     terminal's default background.

	      se=36  SGR substring for separators that	are  inserted  between
		     selected  line  fields  (:), between context line fields,
		     (-), and between groups of adjacent  lines	 when  nonzero
		     context  is  specified  (--).  The default is a cyan text
		     foreground over the terminal's default background.

	      ne     Boolean value that prevents clearing to the end  of  line
		     using  Erase  in  Line  (EL) to Right (\33[K) each time a
		     colorized item ends.  This	 is  needed  on	 terminals  on
		     which  EL	is  not	 supported.  It is otherwise useful on
		     terminals for which the  back_color_erase	(bce)  boolean
		     terminfo  capability  does	 not  apply,  when  the chosen
		     highlight colors do not affect the background, or when EL
		     is	 too  slow or causes too much flicker.	The default is
		     false (i.e., the capability is omitted).

	      Note that boolean capabilities have no  =...   part.   They  are
	      omitted (i.e., false) by default and become true when specified.

	      See   the	  Select   Graphic  Rendition  (SGR)  section  in  the
	      documentation of the text terminal that is  used	for  permitted
	      values   and  their  meaning  as	character  attributes.	 These
	      substring values are integers in decimal representation and  can
	      be  concatenated with semicolons.	 grep takes care of assembling
	      the result into a	 complete  SGR	sequence  (\33[...m).	Common
	      values to concatenate include 1 for bold, 4 for underline, 5 for
	      blink, 7 for inverse, 39 for default foreground color, 30 to  37
	      for  foreground  colors,	90  to 97 for 16-color mode foreground
	      colors, 38;5;0 to 38;5;255  for  88-color	 and  256-color	 modes
	      foreground colors, 49 for default background color, 40 to 47 for
	      background colors, 100  to  107  for  16-color  mode  background
	      colors,  and 48;5;0 to 48;5;255 for 88-color and 256-color modes
	      background colors.

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

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

       LC_ALL, LC_MESSAGES, LANG
	      These variables specify the locale for the LC_MESSAGES category,
	      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 requires; otherwise, grep  behaves
	      more  like other GNU programs.  POSIX 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 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_nonoption_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
	      command 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.

EXIT STATUS
       The  exit  status is 0 if selected lines are found, and 1 if not found.
       If an error occurred the exit status is 2.  (Note: POSIX error handling
       code should check for '2' or greater.)

COPYRIGHT
       Copyright 1998-2000, 2002, 2005-2014 Free Software Foundation, Inc.

       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR	 A  PARTICULAR
       PURPOSE.

BUGS
   Reporting Bugs
       Email  bug reports to <bug-grep@gnu.org>, a mailing list whose web page
       is <http://lists.gnu.org/mailman/listinfo/bug-grep>.   grep's  Savannah
       bug tracker is located at <http://savannah.gnu.org/bugs/?group=grep>.

   Known Bugs
       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.

       Back-references are very slow, and may require exponential time.

SEE ALSO
   Regular Manual Pages
       awk(1), cmp(1), diff(1), find(1), gzip(1),  perl(1),  sed(1),  sort(1),
       xargs(1),   zgrep(1),   mmap(2),	  read(2),   pcre(3),	pcresyntax(3),
       pcrepattern(3), terminfo(5), glob(7), regex(7).

   POSIX Programmer's Manual Page
       grep(1p).

   TeXinfo Documentation
       The full documentation for grep is  maintained  as  a  TeXinfo  manual,
       which you can read at http://www.gnu.org/software/grep/manual/.	If the
       info and grep programs are properly installed at your site, the command

	      info grep

       should give you access to the complete manual.

NOTES
       This man page is maintained only fitfully; the  full  documentation  is
       often more up-to-date.

       GNU's not Unix, but Unix is a beast; its plural form is Unixen.

User Commands			 GNU grep 2.16			       GREP(1)
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