GREP(1)

NAME
grep, egrep, fgrep. zgrep - file pattern searcher

SYNOPSIS
grep [-AB num] [-CEFGHLPRSVZabchilnoqsvwx] [-e pattern] [-f file] [file ...]

DESCRIPTION
The grep utilities search the given input files selecting lines that match one or more patterns. By default, a pattern matches an input line if any 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.

The grep utility is used for simple patterns and ex(1) or ed(1) style regular expressions. The egrep utility can handle extended regular expressions and multi-line patterns. The fgrep utility is quick but can handle only fixed patterns consisting of one or more lines, allowing any of the pattern lines to match a portion of the input. The zgrep utility acts like grep, but accepts input files compressed with the compress(1) or gzip(1) compression utilities.

The following options are available:

-A num
    Print num lines of trailing context after each match.

-B num
    Print num lines of leading context before each match.

-C  Equivalent to -A 2 -B 2.

-E  Force grep to behave as egrep.

-F  Force grep to behave as fgrep.

-G  Force grep to behave as grep.

-H  If -R is specified, follow symbolic links only if they were explictly listed on the command line.

-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 pathname ‘-’ is written.

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

-R  Recursively search subdirectories listed.

-S  If -R is specified, all symbolic links are followed.

-V  Display version information.

-Z  Force grep to behave as zgrep.

-a  Do not search in binary files.

-b  The block number on the disk in which a matched pattern is located is displayed in front of the respective matched line.

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

-e expression
    Specify a pattern used during the search of the input. Multiple -e options can be used to specify multiple patterns; an input line is selected if it matches any of the specified patterns.

-f pattern_file
    The pattern is read from the specified file. Trailing newlines in the pattern file are ignored. (Egrep and fgrep only).

-h  Never print filename headers with output lines.

-i  Perform case insensitive matching.

-l  Only the names of files containing selected lines are written to standard output. Pathnames are listed once per file searched. If the standard input is searched, the pathname ‘-’ 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, or -s is specified.

-o  Always print filename headers with output lines.

-q  Suppress normal output.

-s  Silent mode. Nonexistent and unreadable files are ignored.

-v  Selected lines are those not matching the specified patterns.

-w  The expression is searched for as a word (as if surrounded by `\<' and `\>', see ex(1)).

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

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

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.

EXTENDED REGULAR EXPRESSIONS
The following characters are interpreted by egrep:

$   Align the match from the end of the line.
^   Align the match from the beginning of the line.
|   Add another pattern (see example below).
?   Match 1 or less sequential repetitions of the pattern.
+   Match 1 or more sequential repetitions of the pattern.
*   Match 0 or more sequential repetitions of the pattern.
[]  Match any single character or range of characters enclosed in the brackets.
\   Escape special characters which have meaning to egrep, the set of {$,.,^,[,],|,?,+,*,(,)}.

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'

The apostrophes assure the entire expression is evaluated by grep instead of by the user's shell. The caret ‘^’ matches the null string at the beginning of a line, and the ‘\’ escapes the ‘’. which would otherwise match any character.

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), sed(1), re_format(7), regex(3), regexp(3)

HISTORY
The grep command appeared in AT&T UNIX.