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UNIX Manual | Commands
							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 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, two variant programs egrep and fgrep are available.	 egrep
       is  the	same  as  grep -E.   fgrep  is	the  same  as grep -F.	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, --fixed-regexp
	      Interpret	 PATTERN  as  a	 list  of  fixed strings, separated by
	      newlines, any of which is to be matched.	(-F  is	 specified  by
	      POSIX,  --fixed-regexp  is an obsoleted alias, please do not use
	      it new scripts.)

       -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.	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 (described under
	      --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 (described under
	      --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	(described  under  --group-separator)  between
	      contiguous groups of matches.  With the  -o  or  --only-matching
	      option, this has no effect and a warning is given.

       --group-separator=SEP
	      Use  SEP	as  a group separator. By default SEP is double hyphen
	      (--).

       --no-group-separator
	      Use empty string as a group separator.

   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.

       -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," "extended" and "perl." 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	 may  not   be
       available on every 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
       Normally, the 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.
       Note,  however,	that  POSIX  only mandates, for programs such as grep,
       cmp, and diff, that the exit status in case of error be greater than 1;
       it  is  therefore  advisable, for the sake of portability, to use logic
       that tests for  this  general  condition	 instead  of  strict  equality
       with 2.

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),  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 2.20			       GREP(1)							
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