NAME
  grep - search lines in files for matching patterns

SYNOPSIS
  egrep [ options ] [ pattern ] [ file ... ]

DESCRIPTION
  The grep commands search the named input files for lines containing a match for the given patterns. Matching lines are printed by default. The standard input is
  searched if no files are given or when the file - is specified.

  There are six variants of grep, each one using a different form of pattern, controlled either by option or the command path base name. Details of each variant
  may be found in regex(3).
    grep  The default basic regular expressions (no alternations.)
    egrep Extended regular expressions (alternations, one or more.)
    pgrep perl(1) regular expressions (lenient extended.)
    xgrep Augmented regular expressions (conjunction, negation.)
    fgrep Fixed string expressions.
    agrep Approximate regular expressions (not implemented.)

OPTIONS
  -G, --basic-regexp
                  grep mode (default): basic regular expression patterns.
  -E, --extended-regexp
                  egrep mode: extended regular expression patterns.
  -X, --augmented-regexp
                  xgrep mode: augmented regular expression patterns.
  -P, --perl-regexp
                  pgrep mode: perl(1) regular expression patterns.
  -F, --fixed-string
                  fgrep mode: fixed string patterns.
  -A, --approximate-regexp
                  agrep mode: approximate regular expression patterns (not implemented.)
  -C, --context[=before[,after]]
                  Set the matched line context before and after count. By default only matched lines are printed. The option value may be omitted. The default
                  value is 2,2.
  -c, --count     Only print a matching line count for each file.
  -e, --expression|pattern|regexp=pattern
                  Specify a matching pattern. More than one pattern implies alternation. If this option is specified then the command line pattern must be omitted.
  -f, --file=pattern-file
                  Each line in pattern-file is a pattern, placed into a single alternating expression.
  -H, --filename|with-filename
                  Prefix each matched line with the containing file name.
  -h, --no-filename
                  Suppress containing file name prefix for each matched line.
  -i, --ignore-case
                  Ignore case when matching.
  -l, --files-with-matches
                  Only print file names with at least one match.
  -L, --files-without-matches
                  Only print file names with no matches.
  -b, --highlight Highlight matches using the ansi terminal bold sequence.
  -v, --invert-match|revert-match
                  Invert the pattern match sense.
  -m, --label     All patterns must be of the form label:pattern. Match and count output will be prefixed by the corresponding label:.
  -O, --lenient   Enable lenient pattern interpretation. This is the default.
  -x, --line-match|line-regexp
                  Force patterns to match complete lines.
  -n, --number|line-number
                  Prefix each matched line with its line number.
  -N, --name=name Set the standard input file name prefix to name. The default value is empty.
  -q, --quiet|silent
                  Do not print matching lines.
  -S, --strict    Enable strict pattern interpretation with diagnostics.
  -s, --suppress|no-messages
                  Suppress error and warning messages.
  -t, --total     Only print a single matching line count for all files.
  -T, --test=test Enable implementation specific tests.
  -w, --word-match|word-regexp
                  Force patterns to match complete words.
  -a              Ignored for GNU compatibility.

DIAGNOSTICS
  Exit status 0 if matches were found, 1 if no matches were found, where -v invertes the exit status. Exit status 2 for other errors that are accompanied by a
  message on the standard error.

SEE ALSO
  ed(1), sed(1), perl(1), regex(3)

CAVEATS
  Some expressions of necessity require exponential space and/or time.

BUGS
  Some expressions may use sub-optimal algorithms. For example, don't use this implementation to compute primes.

IMPLEMENTATION
  version         grep (AT&T Research) 2006-06-14
  author          Glenn Fowler <gsf@research.att.com>
  author          David Korn <dgk@research.att.com>
  copyright       Copyright (c) 1992-2009 AT&T Intellectual Property
  license         http://www.opensource.org/licenses/cpl1.0.txt