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fgrep(1)

NAME

       grep,  egrep,  fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep -
       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, two variant programs egrep and fgrep are available.  egrep
       is  the	same  as grep -E.  fgrep is the same as grep -F.  zgrep is the
       same as grep -Z.  zegrep is the same as grep -EZ.  zfgrep is  the  same
       as grep -FZ.

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.

       -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
	      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.

       --colour[=WHEN], --color[=WHEN]
       -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
	      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
	      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.

       --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
	      Flush output on every line.  Note that this incurs a performance
	      penalty.

       -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 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
	      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.

       --null Output  a  zero  byte  (the  ASCII NUL character) instead of the
	      character that normally follows a file name.  For example,  grep
	      -l  --null  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, --decompress
	      Decompress the input data before searching.  This option is only
	      available if compiled with zlib(3) library.

       -J, --bz2decompress
	      Decompress  the bzip2(1) compressed input data before searching.

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 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.
       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-
       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.

       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

       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
       (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".

DIAGNOSTICS

       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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