Provided by: grep_2.16-1_amd64 bug

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.