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.ig
	@(#)grep.1	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH GREP 1
.UC 4
.SH NAME
grep, egrep, fgrep \- search a file for a pattern
.SH SYNOPSIS
.B grep
[ option ] ...
expression [ file ] ...
.LP
.B egrep 
[ option ] ...
[ expression ]
[ file ] ...
.PP
.B fgrep
[ option ] ...
[ strings ]
[ file ]
.SH DESCRIPTION
Commands of the
.I grep
family search the input
.I files
(standard input default)
for lines matching
a pattern.
Normally, each line found
is copied to the standard output.
.I Grep
patterns are limited regular expressions in the style of
.IR ex (1);
it uses a compact nondeterministic algorithm.
.I Egrep
patterns are full regular expressions;
it uses a fast deterministic algorithm that
sometimes needs exponential space.
.I Fgrep
patterns are fixed strings; it is fast and compact.
The following options are recognized.
.TP
.B \-v
All lines but those matching
are printed.
.TP
.B \-x
(Exact) only lines matched in their entirety are printed
.RI ( fgrep
only).
.TP
.B \-c
Only a count of matching lines is printed.
.TP
.B \-l
The names of files with matching lines are listed (once)
separated by newlines.
.TP
.B \-n
Each line is preceded by
its relative line number in the file.
.TP
.B \-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.
.TP
.B \-i
The case of letters is ignored in making comparisons.
(E.g. upper and lower case are considered identical.)
(\fIgrep\fR\| and \fIfgrep\fR only)
.TP
.B \-s
Silent mode.
Nothing is printed (except error messages).
This is useful for checking the error status.
.TP
.B \-w
The expression is searched for as a word
(as if surrounded by `\e<' and `\e>', see
.IR ex (1).)
(\fIgrep\fR\| only)
.TP
.BI \-e " expression"
Same as a simple
.I expression 
argument,
but useful when the
.I expression
begins with a \-.
.TP
.BI \-f " file"
The regular expression
.RI ( egrep )
or string list
.RI ( fgrep ) 
is taken from the
.I file.
.PP
In all cases the file name is shown if there is more than one input file.
Care should be taken when
using the characters
$ * [ ^ | ( ) and \\ in the
.I expression
as they are
also meaningful to the Shell.
It is safest to enclose the
entire
.I expression
argument in single quotes ` '.
.PP
.I Fgrep
searches for lines that contain one of the (newline-separated)
.I strings.
.PP
.I Egrep
accepts extended regular expressions.
In the following description `character' excludes
newline:
.IP
A \e followed by a single character
other than newline
matches that character.
.IP
The character ^ ($) matches the beginning (end) of
a line.
.IP
A 
.B .
matches any character.
.IP
A single character not otherwise endowed with special
meaning matches that character.
.IP
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.
.IP
A regular expression followed by * (+, ?) matches a sequence
of 0 or more (1 or more, 0 or 1)
matches of the regular expression.
.IP
Two regular expressions concatenated
match a match of the first followed by a match of 
the second.
.IP
Two regular expressions separated by | or newline
match either a match for the first or a match for the
second.
.IP
A regular expression enclosed in parentheses
matches a match for the regular expression.
.LP
The order of precedence of operators
at the same parenthesis level
is [\|] then
*+? then concatenation then | and newline.
.SH "SEE ALSO"
ex(1),
sed(1),
sh(1)
.SH DIAGNOSTICS
Exit status is 0 if any matches are found,
1 if none, 2 for syntax errors or inaccessible files.
.SH BUGS
Ideally there should be only one
.I grep,
but we don't know a single algorithm that spans a wide enough
range of space-time tradeoffs.
.PP
Lines
are limited to 256 characters;
longer lines are truncated.
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