GREP(1)

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

SYNOPSIS
grep [-EFGLVZabchilnqosvwx] [-e pattern] [-f file] [file ...]

DESCRIPTION
The grep utilities search the given input files selecting lines which match one or more patterns; the type of patterns is controlled by the options specified. By default, a pattern matches an input line if any regular expression (RE) in the pattern matches the input line without its trailing <new-line>. A null RE matches every line. Each input line that matches at least one of the patterns is written to the standard output.

For simple patterns or ex(1) or ed(1) style regular expressions, the grep utility is used. The egrep utility can handle extended regular expressions and embedded <newline>s in patterns. The fgrep utility is quick but can handle only fixed strings. A fixed string is a string of characters, each character is matched only by itself. The pattern value can consist of multiple lines with embedded <newline>s. In this case, the <newline>s act as alternation characters, allowing any of the pattern lines to match a portion of the input. The zgrep utility acts like grep, but decompresses the input files if they were compressed with the gzip(1) compression utility.

The following options are available:

-E  Force grep to behave as egrep

-F  Force grep to behave as fgrep

-G  Force grep to behave as grep

-Z  Force grep to behave as zgrep

-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.

-V  Display version information

-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 file named by the pathname pattern_file. Trailing newlines in the pattern_file are ignored. (Egrep and fgrep only).

-h  Never print filename headers with output lines.

-i  The case of letters is ignored in making comparisons - that is, upper and lower case are considered identical.

-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; each 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 users shell. The carat or hat ‘^’ means from 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), regex(3), regexp(3)

HISTORY
The grep command appeared in AT&T UNIX.