GREP(1)                    OpenBSD Reference Manual                    GREP(1)

NAME
     grep, egrep, fgrep, zgrep, zegrep, zfgrep - file pattern searcher

SYNOPSIS
     grep [-abcEFGHhIiLlnoPqRSsUVvwxZ] [-A num] [-B num] [-C[num]]
          [-e pattern] [-f file] [--binary-files=value] [--context[=num]]
          [--line-buffered] [pattern] [file ...]

DESCRIPTION
     The grep utility searches any given input files, selecting lines that
     match one or more patterns.  By default, a pattern matches an input line
     if the regular expression (RE) in the pattern matches the input line
     without its trailing newline.  An empty expression matches every line.
     Each input line that matches at least one of the patterns is written to
     the standard output.

     grep is used for simple patterns and basic regular expressions (BREs);
     egrep can handle extended regular expressions (EREs).  See re_format(7)
     for more information on regular expressions.  fgrep is quicker than both
     grep and egrep, but can only handle fixed patterns (i.e. it does not in-
     terpret regular expressions).  Patterns may consist of one or more lines,
     allowing any of the pattern lines to match a portion of the input.

     zgrep, zegrep, and zfgrep act like grep, egrep, and fgrep, respectively,
     but accept input files compressed with the compress(1) or gzip(1) com-
     pression utilities.

     The following options are available:

     -A num  Print num lines of trailing context after each match.  See also
             the -B and -C options.

     -a      Treat all files as ASCII text.  Normally grep will simply print
             ``Binary file ... matches'' if files contain binary characters.
             Use of this option forces grep to output lines matching the spec-
             ified pattern.

     -B num  Print num lines of leading context before each match.  See also
             the -A and -C options.

     -b      The offset in bytes of a matched pattern is displayed in front of
             the respective matched line.

     -C[num]
             Print num lines of leading and trailing context surrounding each
             match.  The default is 2 and is equivalent to -A 2 -B 2.  Note:
             no whitespace may be given between the option and its argument.

     -c      Only a count of selected lines is written to standard output.

     -E      Interpret pattern as an extended regular expression (i.e. force
             grep to behave as egrep).

     -e pattern
             Specify a pattern used during the search of the input: an input
             line is selected if it matches any of the specified patterns.
             This option is most useful when multiple -e options are used to
             specify multiple patterns, or when a pattern begins with a dash
             (`-').

     -F      Interpret pattern as a set of fixed strings (i.e. force grep to
             behave as fgrep).

     -f file
             Read one or more newline separated patterns from file.  Empty
             pattern lines match every input line.  Newlines are not consid-
             ered part of a pattern.  If file is empty, nothing is matched.

     -G      Interpret pattern as a basic regular expression (i.e. force grep
             to behave as traditional grep).

     -H      If -R is specified, follow symbolic links only if they were ex-
             plicitly listed on the command line.  The default is not to fol-
             low symbolic links.

     -h      Never print filename headers (i.e. filenames) with output lines.

     -I      Ignore binary files.

     -i      Perform case insensitive matching.  By default, grep is case sen-
             sitive.

     -L      Only the names of files not containing selected lines are written
             to standard output.  Pathnames are listed once per file searched.
             If the standard input is searched, the string ``(standard
             input)'' is written.

     -l      Only the names of files containing selected lines are written to
             standard output.  grep will only search a file until a match has
             been found, making searches potentially less expensive.  Path-
             names are listed once per file searched.  If the standard input
             is searched, the string ``(standard input)'' is written.

     -n      Each output line is preceded by its relative line number in the
             file, starting at line 1.  The line number counter is reset for
             each file processed.  This option is ignored if -c, -L, -l, or -q
             is specified.

     -o      Always print filename headers with output lines.

     -P      If -R is specified, no symbolic links are followed.  This is the
             default.

     -q      Quiet mode: suppress normal output.  grep will only search a file
             until a match has been found, making searches potentially less
             expensive.

     -R      Recursively search subdirectories listed.

     -S      If -R is specified, all symbolic links are followed.  The default
             is not to follow symbolic links.

     -s      Silent mode.  Nonexistent and unreadable files are ignored (i.e.
             their error messages are suppressed).

     -U      Search binary files, but do not attempt to print them.

     -V      Display version information.  All other options are ignored.

     -v      Selected lines are those not matching any of the specified pat-
             terns.

     -w      The expression is searched for as a word (as if surrounded by
             `[[:<:]]' and `[[:>:]]'; see re_format(7)).

     -x      Only input lines selected against an entire fixed string or regu-
             lar expression are considered to be matching lines.

     -Z      Force grep to behave as zgrep.

     --binary-files=value
             Controls searching and printing of binary files.  Options are
             binary, the default: search binary files but do not print them;
             without-match: do not search binary files; and text: treat all
             files as text.

     --context[=num]
             Print num lines of leading and trailing context.  The default is
             2.

     --line-buffered
             Force output to be line buffered.  By default, output is line
             buffered when standard output is a terminal and block buffered
             otherwise.

     If no file arguments are specified, the standard input is used.

RETURN VALUES
     The grep utility exits with one of the following values:

     0     One or more lines were selected.
     1     No lines were selected.
     >1    An error occurred.

EXAMPLES
     To find all occurrences of the word `patricia' in a file:

           $ grep 'patricia' myfile

     To find all occurrences of the pattern `.Pp' at the beginning of a line:

           $ grep '^\.Pp' myfile

     The apostrophes ensure the entire expression is evaluated by grep instead
     of by the user's shell.  The caret `^' matches the null string at the be-
     ginning of a line, and the `\' escapes the `.', which would otherwise
     match any character.

     To find all lines in a file which do not contain the words `foo' or
     `bar':

           $ grep -v -e 'foo' -e 'bar' myfile

     A simple example of an extended regular expression:

           $ egrep '19|20|25' calendar

     Peruses the file `calendar' looking for either 19, 20, or 25.

SEE ALSO
     ed(1), ex(1), gzip(1), sed(1), re_format(7)

STANDARDS
     The grep utility is compliant with the IEEE Std 1003.1-2008 (``POSIX'')
     specification.

     The flags [-AaBbCGHhILoPRSUVwZ] are extensions to that specification, and
     the behaviour of the -f flag when used with an empty pattern file is left
     undefined.

     All long options are provided for compatibility with GNU versions of this
     utility.

     Historic versions of the grep utility also supported the flags [-ruy].
     This implementation supports those options; however, their use is strong-
     ly discouraged.

HISTORY
     The grep command first appeared in Version 6 AT&T UNIX.

OpenBSD 4.7                    February 8, 2009                              4
