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,  which means that directories are read
              just  as  if  they  were  ordinary  files.   If  ACTION  is  skip,
              directories  are  silently  skipped.   If  ACTION is recurse, grep
              reads  all  files  under  each  directory,  recursively;  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, -r, --recursive
              Read   all  files  under  each  directory,  recursively;  this  is
              equivalent to the -d recurse option.

   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  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.
       {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.2 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.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_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, 2005-2012 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.   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
       GNU's not Unix, but Unix is a beast; its plural form is Unixen.



User Commands                     GNU grep 2.12                          GREP(1)