GRE(1) GRE(1)
NAME
gre, grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
gre [ option ... ] pattern [ file ... ]
grep [ option ... ] pattern [ file ... ]
egrep [ option ... ] pattern [ file ... ]
fgrep [ option ... ] strings [ file ... ]
DESCRIPTION
Gre searches the input files (standard input default) for
lines (with newlines excluded) that match the pattern, a
regular expression as defined in re(3). A file name of - is
interpreted as standard input. Normally, each line matching
the pattern is `selected', and each selected line is copied
to the standard output. The options are
-1 Print only the first selected line of each file argu-
ment.
-b Mark each printed line with its byte position in its
file. This is sometimes useful in locating patterns in
non-text files.
-c Print only a count of matching lines.
-e pattern
Same as a simple pattern argument, but useful when
pattern begins with a -.
-E Simulate egrep.
-f file
Read the pattern from file; there is no pattern argu-
ment
-F Simulate fgrep.
-G Simulate grep.
-h Do not print filename tags (headers) with output lines.
-i Ignore alphabetic case distinctions.
-l Print the names of files with selected lines; don't
print the lines.
-L Print the names of files with no selected lines; the
converse of -l.
-n Mark each printed line with its line number counted in
its file.
-s Produce no output, but return status.
-v Reverse: print lines that do not match the pattern.
-x Exact match: The pattern is ^(pattern)$. The implicit
parentheses count in back references.
Output lines are tagged by filename when there is more than
one input file. (To force this tagging, include /dev/null
GRE(1) GRE(1)
as a filename argument.) If the output line exceeds some
internal limit, a warning is given and a small block of text
surrounding the match is printed.
Care should be taken when using the shell metacharacters
$*[^|()\ and newline in pattern; it is safest to enclose the
entire expression in single quotes '...'.
Gre supplants three classic programs, which are still avail-
able:
Grep handles only ed(1)-like regular expressions. It uses
`\(\)' instead of `()'.
Egrep handles the same patterns as gre except for back-
referencing with \1, \2, ...
Fgrep handles no operators except newline (alternation).
SEE ALSO
re(3), awk(1), sed(1), sam(9.1), strings(1)
DIAGNOSTICS
Exit status is 0 if any lines are selected, 1 if none, 2 for
syntax errors, inaccessible files (even if matches were
found). Warnings will be given for input lines that exceed
a (generous) internal limit.
BUGS
Grep, egrep, and fgrep do not support some options and print
(approximate) block numbers rather than byte numbers for
option -b.
Egrep may fail on input containing characters greater than
0176.