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GREP(1) 							       GREP(1)



NAME
       grep, egrep, fgrep, rgrep - print lines matching a pattern

SYNOPSIS
       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]

DESCRIPTION
       grep  searches the named input FILEs (or standard input if no files are
       named, or the file name - is given) 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 avail
       able.  egrep is the same as grep -E.  fgrep is  the  same  as  grep -F.
       rgrep is the same as grep -r.

OPTIONS
       -A NUM, --after-context=NUM
	      Print  NUM  lines  of  trailing  context	after  matching lines.
	      Places  a  line  containing  --  between	contiguous  groups  of
	      matches.

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

       -B NUM, --before-context=NUM
	      Print NUM  lines	of  leading  context  before  matching	lines.
	      Places  a  line  containing  --  between	contiguous  groups  of
	      matches.

       -b, --byte-offset
	      Print the byte offset within the input file before each line  of
	      output.

       --binary-files=TYPE
	      If the first few bytes of a file indicate that the file contains
	      binary data, assume that the file is of type TYPE.  By  default,
	      TYPE is binary, and grep normally outputs either a one-line mes
	      sage saying that a binary file matches, or no message  if  there
	      is  no  match.   If  TYPE  is without-match, grep assumes that a
	      binary file does not match; this is equivalent to the -I option.
	      If  TYPE	is  text,  grep  processes a binary file as if it were
	      text; this is  equivalent  to  the  -a  option.	Warning:  grep
	      --binary-files=text  might output binary garbage, which can have
	      nasty side effects if the output is a terminal and if the termi
	      nal driver interprets some of it as commands.

       -C NUM, --context=NUM
	      Print  NUM lines of output context.  Places a line containing --
	      between contiguous groups of matches.

       -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.

       --colour[=WHEN], --color[=WHEN]
	      Surround the matching string with the marker find in  GREP_COLOR
	      environment variable. WHEN may be never, always, or auto

       -D ACTION, --devices=ACTION
	      If an input file is a device, FIFO or socket, use ACTION to pro
	      cess it.	By default, ACTION is read, which means  that  devices
	      are  read  just  as  if  they were ordinary files.  If ACTION is
	      skip, devices are silently skipped.

       -d ACTION, --directories=ACTION
	      If an input file is a directory, use ACTION to process  it.   By
	      default,	ACTION	is read, which means that directories are read
	      just as if they were ordinary files.  If ACTION is skip,	direc
	      tories  are  silently skipped.  If ACTION is recurse, grep reads
	      all files under each directory, recursively; this is  equivalent
	      to the -r option.

       -E, --extended-regexp
	      Interpret PATTERN as an extended regular expression (see below).

       -e PATTERN, --regexp=PATTERN
	      Use PATTERN as the pattern; useful to protect patterns beginning
	      with -.

       -F, --fixed-strings
	      Interpret  PATTERN as a list of fixed strings, separated by new
	      lines, any of which is to be matched.

       -f FILE, --file=FILE
	      Obtain patterns from FILE, one per line.	The  empty  file  con
	      tains zero patterns, and therefore matches nothing.

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

       -H, --with-filename
	      Print the filename for each match.

       -h, --no-filename
	      Suppress the prefixing of  filenames  on	output	when  multiple
	      files are searched.

       --help Output a brief help message.

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

       -i, --ignore-case
	      Ignore case distinctions in  both  the  PATTERN  and  the  input
	      files.

       -L, --files-without-match
	      Suppress	normal	output;  instead  print the name of each input
	      file from which no output would normally have been printed.  The
	      scanning will stop on the first match.

       -l, --files-with-matches
	      Suppress	normal	output;  instead  print the name of each input
	      file from which output would normally have  been	printed.   The
	      scanning will stop on the first match.

       --label=LABEL
	      Displays input actually coming from standard input as input com
	      ing from file LABEL.  This is especially useful for  tools  like
	      zgrep, e.g.  gzip -cd foo.gz |grep --label=foo something

       --line-buffered
	      Use line buffering, it can be a performance penalty.

       -m NUM, --max-count=NUM
	      Stop  reading  a file after NUM matching lines.  If the input is
	      standard input from a regular file, and NUM matching  lines  are
	      output,  grep  ensures  that the standard input is positioned to
	      just after the last matching line before exiting, regardless  of
	      the  presence of trailing context lines.	This enables a calling
	      process to resume a search.  When grep stops after NUM  matching
	      lines,  it  outputs  any trailing context lines.	When the -c or
	      --count option is also  used,  grep  does  not  output  a  count
	      greater  than NUM.  When the -v or --invert-match option is also
	      used, grep stops after outputting NUM non-matching lines.

       --mmap If possible, use the mmap(2) system call to read input,  instead
	      of  the default read(2) system call.  In some situations, --mmap
	      yields better performance.  However, --mmap can cause  undefined
	      behavior	(including  core dumps) if an input file shrinks while
	      grep is operating, or if an I/O error occurs.

       -n, --line-number
	      Prefix each line of output with the line number within its input
	      file.

       -o, --only-matching
	      Show only the part of a matching line that matches PATTERN.

       -P, --perl-regexp
	      Interpret PATTERN as a Perl regular expression.

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

       -R, -r, --recursive
	      Read all files under each directory, recursively; this is equiv
	      alent to the -d recurse option.

	 --include=PATTERN
	      Recurse in directories only searching file matching PATTERN.

	 --exclude=PATTERN
	      Recurse in directories skip file matching PATTERN.

       -s, --no-messages
	      Suppress error messages about nonexistent or  unreadable	files.
	      Portability note: unlike GNU grep, traditional grep did not con
	      form to POSIX.2, because traditional grep lacked a -q option and
	      its  -s option behaved like GNU greps -q option.	Shell scripts
	      intended to be portable to traditional grep should avoid both -q
	      and -s and should redirect output to /dev/null instead.

       -U, --binary
	      Treat  the  file(s) as binary.  By default, under MS-DOS and MS-
	      Windows, grep guesses the file type by looking at  the  contents
	      of  the first 32KB read from the file.  If grep decides the file
	      is a text file, it strips the CR characters  from  the  original
	      file  contents  (to  make  regular expressions with ^ and $ work
	      correctly).  Specifying -U overrules this guesswork, causing all
	      files  to be read and passed to the matching mechanism verbatim;
	      if the file is a text file with CR/LF pairs at the end  of  each
	      line,  this  will  cause some regular expressions to fail.  This
	      option has no effect on platforms other than MS-DOS and  MS-Win
	      dows.

       -u, --unix-byte-offsets
	      Report  Unix-style  byte	offsets.   This  switch causes grep to
	      report byte offsets as if the file were  Unix-style  text  file,
	      i.e. with CR characters stripped off.  This will produce results
	      identical to running grep on a Unix machine.  This option has no
	      effect  unless -b option is also used; it has no effect on plat
	      forms other than MS-DOS and MS-Windows.

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

       -v, --invert-match
	      Invert the sense of matching, to select non-matching lines.

       -w, --word-regexp
	      Select  only  those  lines  containing  matches  that form whole
	      words.  The test is that the matching substring must  either  be
	      at  the  beginning  of  the line, or preceded by a non-word con
	      stituent character.  Similarly, it must be either at the end  of
	      the line or followed by a non-word constituent character.  Word-
	      constituent characters are letters, digits, and the  underscore.

       -x, --line-regexp
	      Select only those matches that exactly match the whole line.

       -y     Obsolete synonym for -i.

       -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.

       -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  expres
       sions, 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 using either of the first two syntaxes.  In
       other implementations, basic regular  expressions  are  less  powerful.
       The following description applies to extended regular expressions; dif
       ferences for basic regular expressions are summarized afterwards.  Perl
       regular	expressions  add additional functionality, but the implementa
       tion used here is undocumented and is not compatible  with  other  grep
       implementations.

       The  fundamental building blocks are the regular expressions that match
       a single character.  Most characters, including all letters and digits,
       are  regular expressions that match themselves.	Any metacharacter with
       special meaning may be quoted by preceding it with a backslash.

       A bracket expression is a list of characters enclosed by [ and  ].   It
       matches	any  single  character in that list; if the first character of
       the list is the caret ^ then it matches any character not in the  list.
       For  example,  the  regular  expression [0123456789] matches any single
       digit.

       Within a bracket expression, a range expression consists of two charac
       ters separated by a hyphen.  It matches any single character that sorts
       between the two characters, inclusive,  using  the  locales  collating
       sequence  and  character  set.	For  example, in the default C locale,
       [a-d] is equivalent to [abcd].  Many locales sort characters in dictio
       nary  order,  and in these locales [a-d] is typically not equivalent to
       [abcd]; it might be equivalent to [aBbCcDd], for  example.   To	obtain
       the  traditional interpretation of bracket expressions, you can use the
       C locale by setting the LC_ALL environment variable to the value C.

       Finally, certain named classes  of  characters  are  predefined	within
       bracket expressions, as follows.  Their names are self explanatory, and
       they  are  [:alnum:],  [:alpha:],  [:cntrl:],   [:digit:],   [:graph:],
       [:lower:],  [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
       For example, [[:alnum:]] means  [0-9A-Za-z],  except  the  latter  form
       depends upon the C locale and the ASCII character encoding, whereas the
       former is independent of locale and  character  set.   (Note  that  the
       brackets  in these class names are part of the symbolic names, and must
       be included in addition to the brackets delimiting the  bracket	list.)
       Most  metacharacters  lose  their  special  meaning  inside  lists.  To
       include a literal ] place it first in the list.	Similarly, to  include
       a literal ^ place it anywhere but first.  Finally, to include a literal
       - place it last.

       The period .  matches any single character.  The symbol \w is a synonym
       for [[:alnum:]] and \W is a synonym for [^[:alnum]].

       The  caret ^ and the dollar sign $ are metacharacters that respectively
       match the empty string at the beginning and end of a line.  The symbols
       \<  and \> respectively match the empty string at the beginning and end
       of a word.  The symbol \b matches the empty string at  the  edge  of  a
       word,  and \B matches the empty string provided its not at the edge of
       a word.

       A regular expression may be followed by one of several repetition oper
       ators:
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {n,m}  The  preceding  item  is	matched at least n times, but not more
	      than m times.

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

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

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

       The backreference \n, where n is a single digit, matches the  substring
       previously  matched by the nth parenthesized subexpression of the regu
       lar expression.

       In basic regular expressions the metacharacters ?, +, {, |,  (,	and  )
       lose  their  special  meaning; instead use the backslashed versions \?,
       \+, \{, \|, \(, and \).

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

       GNU egrep attempts to support traditional usage by assuming that  {  is
       not  special if it would be the start of an invalid interval specifica
       tion.  For example, the shell command egrep {1 searches for the	two-
       character  string {1 instead of reporting a syntax error in the regular
       expression.  POSIX.2 allows this behavior as an extension, but portable
       scripts should avoid it.

ENVIRONMENT VARIABLES
       greps behavior is affected by the following environment variables.

       A  locale  LC_foo is specified by examining the three environment vari
       ables LC_ALL, LC_foo, LANG, in that order.  The first  of  these  vari
       ables  that is set specifies the locale.  For example, if LC_ALL is not
       set, but LC_MESSAGES is set to pt_BR, then Brazilian Portuguese is used
       for  the  LC_MESSAGES  locale.	The  C locale is used if none of these
       environment variables  are  set,  or  if  the  locale  catalog  is  not
       installed,  or  if grep was not compiled with national language support
       (NLS).

       GREP_OPTIONS
	      This variable specifies default options to be placed in front of
	      any   explicit   options.    For	example,  if  GREP_OPTIONS  is
	      --binary-files=without-match --directories=skip, grep  behaves
	      as  if the two options --binary-files=without-match and --direc
	      tories=skip had been  specified  before  any  explicit  options.
	      Option  specifications are separated by whitespace.  A backslash
	      escapes the next character, so it can  be  used  to  specify  an
	      option containing whitespace or a backslash.

       GREP_COLOR
	      Specifies the marker for highlighting.

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

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

       LC_ALL, LC_MESSAGES, LANG
	      These variables specify the LC_MESSAGES locale, which determines
	      the  language that grep uses for messages.  The default C locale
	      uses American English messages.

       POSIXLY_CORRECT
	      If set,  grep  behaves  as  POSIX.2  requires;  otherwise,  grep
	      behaves  more  like  other  GNU programs.  POSIX.2 requires that
	      options that follow file names must be treated as file names; by
	      default,	such  options are permuted to the front of the operand
	      list and are treated as options.	Also,  POSIX.2	requires  that
	      unrecognized  options  be diagnosed as illegal, but since they
	      are not really against the law the default is to	diagnose  them
	      as   invalid.   POSIXLY_CORRECT  also  disables  _N_GNU_nonop
	      tion_argv_flags_, described below.

       _N_GNU_nonoption_argv_flags_
	      (Here N is greps numeric process ID.)  If the ith character  of
	      this  environment variables 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 com
	      mand 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.

DIAGNOSTICS
       Normally, exit status is 0 if selected lines are found and 1 otherwise.
       But the exit status is 2 if an error occurred, unless the -q or --quiet
       or --silent option is used and a selected line is found.

BUGS
       Email  bug  reports  to	bug-gnu-utils@gnu.org.	Be sure to include the
       word grep somewhere in the Subject: field.

       Large repetition counts in the {n,m} construct may cause  grep  to  use
       lots of memory.	In addition, certain other obscure regular expressions
       require exponential time and space, and may cause grep to  run  out  of
       memory.

       Backreferences are very slow, and may require exponential time.



GNU Project			  2002/01/22			       GREP(1)




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