GREP(1) 						      General Commands Manual							   GREP(1)

NAME

       grep, egrep, fgrep - 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.

OPTIONS

       -A NUM, --after-context=NUM
	      Print NUM lines of trailing context after matching lines.

       -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.

       -C [NUM], -NUM, --context[=NUM]
	      Print NUM lines (default 2) of output context.

       -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 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.

       -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, --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.

       -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 newlines, any of which is to be matched.

       -f FILE, --file=FILE
	      Obtain patterns from FILE, one per line.	The empty file contains 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  scan-
	      ning 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.

       --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.

       -q, --quiet, --silent
	      Quiet; suppress normal output.  The scanning will stop on the first match.  Also see the -s or --no-messages option below.

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

       -s, --no-messages
	      Suppress error messages about nonexistent or unreadable files.  Portability note: unlike GNU grep, traditional grep did not  conform
	      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-Windows.

       -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 platforms other than MS-DOS and MS-Windows.

       -V, --version
	      Print the version number of grep to standard error.  This version 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 constituent character.  Similarly, it must be either at the end of the line or fol-
	      lowed 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 out-
	      puts  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.

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
       available  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 dig-
       its, are regular expressions that match themselves.  Any metacharacter with special meaning may be quoted by preceding it with a backslash.

       A  list of characters enclosed by [ and ] 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.  A range  of  charac-
       ters  may  be  specified  by giving the first and last characters, separated by a hyphen.  Finally, certain named classes of characters are
       predefined.  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 POSIX
       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 metachar-
       acters 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 sym-
       bols < and > respectively match the empty string at the beginning and end of a word.  The symbol  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 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.

       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 
, where n is a single digit, matches the substring previously matched by the nth  parenthesized  subexpression  of  the
       regular 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 specifi-
       cation.	For example, the shell command egrep '{1' searches for the two-character string {1 instead of reporting a syntax error in the reg-
       ular expression.  POSIX.2 allows this behavior as an extension, but portable scripts should avoid it.

ENVIRONMENT VARIABLES

       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 char-
	      acter, so it can be used to specify an option containing whitespace or a backslash.

       LC_ALL, LC_MESSAGES, LANG
	      These variables specify the LC_MESSAGES locale, which determines the language that grep uses for messages.  The locale is determined
	      by  the  first  of  these variables that is set.	American English is used if none of these environment variables are set, or if the
	      message catalog is not installed, or if grep was not compiled with national language support (NLS).

       LC_ALL, LC_CTYPE, LANG
	      These variables specify the LC_CTYPE locale, which determines the type of characters, e.g., which characters  are  whitespace.   The
	      locale  is  determined by the first of these variables that is set.  The POSIX 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).

       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  op-
	      erand  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.

DIAGNOSTICS

       Normally,  exit	status	is 0 if matches were found, and 1 if no matches were found.  (The -v option inverts the sense of the exit status.)
       Exit status is 2 if there were syntax errors in the pattern, inaccessible input files, or other system errors.

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 {m,n} construct may cause grep to use lots of memory.  In addition, certain other  obscure  regular  expres-
       sions 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							    2002/04/30								   GREP(1)