term% cat index.txt GREP(1) General Commands Manual GREP(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
grep [ options ] expression [ files ]
egrep [ options ] [ expression ] [ files ]
fgrep [ options ] [ strings ] [ files ]
DESCRIPTION
Commands of the grep family search the input files (standard input de‐
fault) for lines matching a pattern. Normally, each line found is
copied to the standard output. Grep patterns are limited regular ex‐
pressions in the style of ed(1); it uses a compact non-deterministic
algorithm. Egrep patterns are full regular expressions; it uses a fast
deterministic algorithm. Fgrep patterns are fixed strings; it is fast
and compact. The following options are recognized:
-v All lines but those matching are printed.
-x (Exact) only lines matched in their entirety are printed (fgrep
only).
-c Only a count of matching lines is printed.
-i Ignore alphabetic case distinctions.
-l Only the names of files with matching lines are listed (once),
separated by new-lines.
-n Each line is preceded by its relative 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 con‐
text.
-h Do not print filename headers with output lines.
-s No output is produced, only status.
-e expression
Same as a simple expression argument, but useful when the ex‐
pression begins with a -.
-f file
The regular expression (egrep) or strings list (fgrep) is taken
from the file.
Output lines are tagged by filename when there is more than one input
file. Care should be taken when using the shell metacharacters
$*[^|()\ in expression; it is safest to enclose the entire expression
in single quotes ′...′.
Fgrep searches for lines that contain one of the strings separated by
new-lines.
Egrep accepts regular expressions as in ed(1), except for \(, \), and
\n, with the addition of:
1. A regular expression followed by + matches one or more occur‐
rences of the expression.
2. A regular expression followed by ? matches 0 or 1 occurrence.
3. Two regular expressions separated by ⎪ or newline match ocur‐
rences of either.
4. Parentheses () specify grouping.
The order of precedence of operators is [], then ∗?+, then concatena‐
tion, then ⎪ and new-line.
SEE ALSO
ed(1), sed(1), sh(1).
DIAGNOSTICS
Exit status is 0 if any matches are found, 1 if none, 2 for syntax er‐
rors or inaccessible files (even if matches were found).
BUGS
Ideally there should be only one grep, but we do not know a single al‐
gorithm that spans a wide enough range of space-time tradeoffs.
Lines are truncated at BUFSIZ characters; see setbuf(3). Null charac‐
ters behave as end-of-line in matches.
GREP(1)