grep, egrep, fgrep - search file for regular expression
grep [option...] expression [file...]
egrep [option...] [expression] [file...]
fgrep [option...] [strings] [file]
Commands of the family search the input files (standard input default)
for lines matching a pattern. Normally, each line found is copied to
the standard output.
The command patterns are limited regular expressions in the style of
which uses a compact nondeterministic algorithm. The command patterns
are full regular expressions. The command uses a fast deterministic
algorithm that sometimes needs exponential space. The command patterns
are fixed strings. The command is fast and compact.
In all cases the file name is shown if there is more than one input
file. Take care when using the characters $ * [ ^ | ( ) and \ in the
expression because they are also meaningful to the Shell. It is safest
to enclose the entire expression argument in single quotes ´ ´.
The command searches for lines that contain one of the (new line-sepa‐
The command accepts extended regular expressions. In the following
description `character' excludes new line:
A backslash (\) followed by a single character other than new
line matches that character.
The circumflex (^) character matches the beginning of a line.
The dollar sign ($) character matches the end of a line.
A dot (.) 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 abbre‐
viated as in `a-z0-9'. A right bracket (]) may occur only as
the first character of the string. A literal dash (-) must be
placed where it can not be mistaken as a range indicator.
A regular expression followed by an asterisk (*) matches a
sequence of 0 or more matches of the regular expression. A reg‐
ular expression followed by a plus (+) matches a sequence of 1
or more matches of the regular expression. A regular expression
followed by a question mark (?) matches a sequence of 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 a vertical bar (|) or new
line match either a match for the first or a match for the sec‐
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
the following: , then *+?, then concatenation, then | and new line.
Options-b Precedes each output line with its block number. This is
sometimes useful in locating disk block numbers by context.
-c Produces count of matching lines only.
Uses next argument as expression that begins with a minus
-f file Takes regular expression or string list from file.
-i Considers uppercase and lowercase letters identical in mak‐
ing comparisons and only).
-l Lists files with matching lines only once, separated by a
-n Precedes each matching line with its line number.
-s Silent mode and nothing is printed (except error messages).
This is useful for checking the error status (see DIAGNOS‐
-v Displays all lines that do not match specified expression.
-w Searches for an expression as for a word (as if surrounded
by `\<' and `\>'). For further information, see only.
-x Prints exact lines matched in their entirety only).
Lines are limited to 256 characters; longer lines are truncated.
When using the option with a string list can not be greater than 6000
bytes minus newline characters
Exit status is 0 if any matches are found, 1 if none, 2 for syntax
errors or inaccessible files.
See Alsoex(1), sed(1), sh(1)grep(1)