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GREP(1)								       GREP(1)

       grep, egrep, fgrep - print lines matching a pattern

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

       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, two variant programs egrep and fgrep are available.	 Egrep
       is the same as grep -E.	Fgrep is the same as grep -F.

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

       -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

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

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

	      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.

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

       -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.

       -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, 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.  -P, --perl-regexp	Inter‐
	      pret PATTERN as a Perl regular expression.

       -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

       -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.

       -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

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

	      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

	      Use line buffering, it can be a performance penality.

       -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.

	      Recurse in directories only searching file matching 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 grep's -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‐

       -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.

       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 two different versions of regular  expression  syntax:
       “basic”	and “extended.”	 In GNU grep, there is no difference in avail‐
       able functionality using	 either	 syntax.   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.

       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

       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  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 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 it's not at the edge of
       a word.

       A regular expression may be followed by one of several repetition oper‐
       ?      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‐

       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.

       Grep's 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

	      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.

	      Specifies the marker for highlighting.

	      These  variables specify the LC_COLLATE locale, which determines
	      the collating sequence used to interpret range expressions  like

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

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

	      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.

	      (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 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.

       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.

       Email  bug  reports  to	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

       Backreferences are very slow, and may require exponential time.

GNU Project			  2002/01/22			       GREP(1)

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