GREP(1) GREP(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
grep [ option ] ... expression [ file ] ...
egrep [ option ] ... [ expression ] [ file ] ...
fgrep [ option ] ... [ strings ] [ file ]
DESCRIPTION
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; unless the -h
flag is used, the file name is shown if there is more than
one input file.
Grep patterns are limited regular expressions in the style
of ed(1); it uses a compact nondeterministic algorithm.
Egrep patterns are full regular expressions; it uses a fast
deterministic algorithm that sometimes needs exponential
space. Fgrep patterns are fixed strings; it is fast and
compact.
The following options are recognized.
-v All lines but those matching are printed.
-c Only a count of matching lines is printed.
-l The names of files with matching lines are listed
(once) separated by newlines.
-n Each line is preceded by its 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.
-s No output is produced, only status.
-h Do not print filename headers with output lines.
-y Lower case letters in the pattern will also match upper
case letters in the input (grep only).
-e expression
Same as a simple expression argument, but useful when
the expression begins with a -.
GREP(1) GREP(1)
-f file
The regular expression (egrep) or string list (fgrep)
is taken from the file.
-x (Exact) only lines matched in their entirety are
printed (fgrep only).
Care should be taken when using the characters $ * [ ^ | ? '
" ( ) and \ in the expression as they are also meaningful to
the Shell. It is safest to enclose the entire expression
argument in single quotes ' '.
Fgrep searches for lines that contain one of the (newline-
separated) strings.
Egrep accepts extended regular expressions. In the follow-
ing description `character' excludes newline:
A \ followed by a single character matches that charac-
ter.
The character ^ ($) matches the beginning (end) of a
line.
A . matches any character.
A single character not otherwise endowed with special
meaning matches that character.
A string enclosed in brackets [] matches any single
character from the string. Ranges of ASCII character
codes may be abbreviated as in `a-z0-9'. A ] may occur
only as the first character of the string. A literal -
must be placed where it can't be mistaken as a range
indicator.
A regular expression followed by * (+, ?) matches a
sequence of 0 or more (1 or more, 0 or 1) matches of
the regular expression.
Two regular expressions concatenated match a match of
the first followed by a match of the second.
Two regular expressions separated by | or newline match
either a match for the first or a match for the second.
A regular expression enclosed in parentheses matches a
match for the regular expression.
The order of precedence of operators at the same parenthesis
level is [] then *+? then concatenation then | and newline.
GREP(1) GREP(1)
SEE ALSO
ed(1), sed(1), sh(1)
DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for
syntax errors or inaccessible files.
BUGS
Ideally there should be only one grep, but we don't know a
single algorithm that spans a wide enough range of space-
time tradeoffs.
Lines are limited to 256 characters; longer lines are trun-
cated.