.TH GREP 1
.SH NAME
grep, egrep, fgrep \- search a file for a pattern
.SH SYNOPSIS
.B grep
[ options ] expression [ files ]
.PP
.B egrep
[ options ] [ expression ] [ files ]
.PP
.B fgrep
[ options ] [ strings ] [ files ]
.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
.IR expression s
in the style of
.IR ed (1);
it uses a compact non-deterministic algorithm.
.I egrep\^
patterns are full regular
.IR expression s;
it
uses a fast deterministic algorithm.
.I fgrep\^
patterns are fixed
.IR strings ;
it is fast and compact.
The following
.I options\^
are recognized:
.TP
.B \-v
All lines but those matching
are printed.
.PD 0
.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 \-i
Ignore alphabetic case distinctions.
.TP
.B \-l
Only the names of files with matching lines are listed (once),
separated by new-lines.
.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 \-h
Do not print filename headers with output lines.
.TP
.B \-s
No output is produced, only status.
.TP
.BI \-e " expression\^"
Same as a simple
.I expression\^
argument,
but useful when the
.I expression\^
begins with a
.BR \- .
.TP
.BI \-f " file\^"
The regular
.I expression\^
.RI ( egrep )
or
.I strings\^
list
.RI ( fgrep )
is taken from the
.IR file .
.PD
.PP
Output lines are tagged by filename when there is more than one
input file.
Care should be taken when
using the shell metacharacters
.B $*[^|()\e
in
.IR expression ;
it is safest to enclose the
entire
.I expression\^
in single quotes
.BR \&\|\(fm \|.\|.\|.\| \(fm .
.PP
.I fgrep\^
searches for lines that contain one of the
.I strings\^
separated by new-lines.
.PP
.I egrep\^
accepts
regular
expressions
as in
.IR ed (1),
except for
.BR \e(,
.BR \e) ,
and
.BI \e n,
with the addition of:
.TP
1.
A regular expression followed by
.B +
matches one or more occurrences of the
expression.
.PD 0
.TP
2.
A regular expression followed by
.B ?
matches 0 or 1 occurrence.
.TP
3.
Two regular expressions separated by \(bv or
newline match ocurrences of either.
.TP
4.
Parentheses
.B (\|)
specify grouping.
.PD
.PP
The order of precedence of operators is
.BR [\|] ,
then
.BR \(**\|?\|+ ,
then concatenation, then \(bv and new-line.
.SH SEE ALSO
ed(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
(even if matches were found).
.SH BUGS
Ideally there should be only one
.IR grep ,
but we do not know a single algorithm that spans a wide enough
range of space-time tradeoffs.
.br
Lines
are truncated at \s-1BUFSIZ\s+1 characters; see
.IR setbuf (3).
Null characters behave as end-of-line in matches.
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