man(1) Manual page archive

     GREP(1)                                                   GREP(1)

          grep, egrep, fgrep - search a file for a pattern

          grep [ options ] expression [ files ]

          egrep [ options ] [ expression ] [ files ]

          fgrep [ options ] [ strings ] [ files ]

          Commands of the grep family search the input files (standard
          input default) for lines matching a pattern.  Normally, each
          line found is copied to the standard output.  Grep patterns
          are limited regular expressions in the style of ed(1); it
          uses a compact non-deterministic algorithm.  Egrep patterns
          are full regular expressions; it uses a fast deterministic
          algorithm.  Fgrep patterns are fixed strings; it is fast and
          compact.  The following options are recognized:

          -v   All lines but those matching are printed.
          -x   (Exact) only lines matched in their entirety are
               printed (fgrep only).
          -c   Only a count of matching lines is printed.
          -i   Ignore alphabetic case distinctions.
          -l   Only the names of files with matching lines are listed
               (once), separated by new-lines.
          -n   Each line is preceded by its relative line number in
               the file.
          -b   Each line is preceded by the block number on which it
               was found.  This is sometimes useful in locating disk
               block numbers by context.
          -h   Do not print filename headers with output lines.
          -s   No output is produced, only status.
          -e expression
               Same as a simple expression argument, but useful when
               the expression begins with a -.
          -f file
               The regular expression (egrep) or strings list (fgrep)
               is taken from the file.

          Output lines are tagged by filename when there is more than
          one input file.  Care should be taken when using the shell
          metacharacters $*[^|()\ in expression; it is safest to
          enclose the entire expression in single quotes '...'.

          Fgrep searches for lines that contain one of the strings
          separated by new-lines.

          Egrep accepts regular expressions as in ed(1), except for

     GREP(1)                                                   GREP(1)

          \(, \), and \n, with the addition of:

          1.   A regular expression followed by + matches one or more
               occurrences of the expression.
          2.   A regular expression followed by ? matches 0 or 1
          3.   Two regular expressions separated by | or newline match
               ocurrences of either.
          4.   Parentheses () specify grouping.

          The order of precedence of operators is [], then *?+, then
          concatenation, then | and new-line.

          ed(1), sed(1), sh(1).

          Exit status is 0 if any matches are found, 1 if none, 2 for
          syntax errors or inaccessible files (even if matches were

          Ideally there should be only one grep, but we do not know a
          single algorithm that spans a wide enough range of space-
          time tradeoffs.
          Lines are truncated at BUFSIZ characters; see setbuf(3).
          Null characters behave as end-of-line in matches.