grep(1) grep(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
grep [-b] [-c] [-i] [-n] [-s] [-v] expression [files]
egrep [-b] [-c] [-e expression] [-f file] [-i] [-n] [-v]
[expression] [files]
fgrep [-b] [-c] [-e expression] [-f file] [-i] [-n] [-v]
[-x] [strings] [files]
DESCRIPTION
Commands of the grep family search the input files (standard
input default) for lines matching a pattern. Normally, each
line found is copied to the standard output. grep patterns
are limited regular expressions 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 that sometimes needs exponential space. fgrep
patterns are fixed strings; it is fast and compact. The
following flag 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 upper/lowercase distinction during
comparisons.
-l Only the names of files with matching lines are
listed (once), separated by newlines.
-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 context.
-s The error messages produced for nonexistent or
unreadable files are suppressed (grep only).
-e expression
Same as a simple expression argument, but
useful when the expression begins with a -
(does not work with grep).
-f file The regular expression (egrep) or strings list
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grep(1) grep(1)
(fgrep) is taken from the file.
In all cases, the file name is output if there is more than
one input file. Care should be taken when using the
characters $, *, [, ^, |, (, ), and \ in expression, because
they are also meaningful to the shell. It is safest to
enclose the entire expression argument in single quotes
'...'.
Fgrep searches for lines that contain one of the strings
separated by newlines.
Egrep accepts regular expressions as in ed(1), except for \(
and \), with the addition of:
1. A regular expression followed by + matches one or more
occurrences of the regular expression.
2. A regular expression followed by ? matches 0 or 1
occurrences of the regular expression.
3. Two regular expressions separated by | or by a newline
match strings that are matched by either.
4. A regular expression may be enclosed in parentheses ()
for grouping.
The order of precedence of operators is [], then *?+, then
concatenation, then | and newline.
EXAMPLE
grep -v -c 'regular' grep.1
reports a count of the number of lines that do not contain
the word regular in the file grep.1.
FILES
/bin/grep
/bin/egrep
/bin/fgrep
SEE ALSO
csh(1), ksh(1), ed(1), sed(1), sh(1).
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).
BUGS
Ideally there should be only one grep, but we do not know a
single algorithm that spans a wide enough range of space-
time tradeoffs.
Lines are limited to BUFSIZ characters; longer lines are
truncated. (BUFSIZ is defined in /usr/include/stdio.h.)
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Egrep does not recognize ranges, such as [a-z], in character
classes.
If there is a line with embedded nulls, grep will only match
up to the first null; if it matches, it will print the
entire line.
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