GREP(1) General Commands Manual GREP(1)
NAME
grep, egrep, fgrep, rgrep, bzgrep, bzegrep, bzfgrep, zgrep, zegrep,
zfgrep – file pattern searcher
SYNOPSIS
grep [-abcdDEFGHhIiJLlMmnOopqRSsUVvwXxZz] [-A num] [-B num] [-C num]
[-e pattern] [-f file] [--binary-files=value] [--color[=when]]
[--colour[=when]] [--context=num] [--label] [--line-buffered]
[--null] [pattern] [file ...]
DESCRIPTION
The grep utility searches any given input files, selecting lines that
match one or more patterns. By default, a pattern matches an input line
if the regular expression (RE) in the pattern matches the input line
without its trailing newline. An empty expression matches every line.
Each input line that matches at least one of the patterns is written to
the standard output.
grep is used for simple patterns and basic regular expressions (BREs);
egrep can handle extended regular expressions (EREs). See re_format(7)
for more information on regular expressions. fgrep is quicker than both
grep and egrep, but can only handle fixed patterns (i.e., it does not
interpret regular expressions). Patterns may consist of one or more
lines, allowing any of the pattern lines to match a portion of the input.
zgrep, zegrep, and zfgrep act like grep, egrep, and fgrep, respectively,
but accept input files compressed with the compress(1) or gzip(1)
compression utilities. bzgrep, bzegrep, and bzfgrep act like grep,
egrep, and fgrep, respectively, but accept input files compressed with
the bzip2(1) compression utility.
The following options are available:
-A num, --after-context=num
Print num lines of trailing context after each match. See also
the -B and -C options.
-a, --text
Treat all files as ASCII text. Normally grep will simply print
“Binary file ... matches” if files contain binary characters.
Use of this option forces grep to output lines matching the
specified pattern.
-B num, --before-context=num
Print num lines of leading context before each match. See also
the -A and -C options.
-b, --byte-offset
The offset in bytes of a matched pattern is displayed in front of
the respective matched line.
-C num, --context=num
Print num lines of leading and trailing context surrounding each
match. See also the -A and -B options.
-c, --count
Only a count of selected lines is written to standard output.
--colour=[when], --color=[when]
Mark up the matching text with the expression stored in the
GREP_COLOR environment variable. The possible values of when are
“never”, “always” and “auto”.
-D action, --devices=action
Specify the demanded action for devices, FIFOs and sockets. The
default action is “read”, which means, that they are read as if
they were normal files. If the action is set to “skip”, devices
are silently skipped.
-d action, --directories=action
Specify the demanded action for directories. It is “read” by
default, which means that the directories are read in the same
manner as normal files. Other possible values are “skip” to
silently ignore the directories, and “recurse” to read them
recursively, which has the same effect as the -R and -r option.
-E, --extended-regexp
Interpret pattern as an extended regular expression (i.e., force
grep to behave as egrep).
-e pattern, --regexp=pattern
Specify a pattern used during the search of the input: an input
line is selected if it matches any of the specified patterns.
This option is most useful when multiple -e options are used to
specify multiple patterns, or when a pattern begins with a dash
(‘-’).
--exclude pattern
If specified, it excludes files matching the given filename
pattern from the search. Note that --exclude and --include
patterns are processed in the order given. If a name matches
multiple patterns, the latest matching rule wins. If no
--include pattern is specified, all files are searched that are
not excluded. Patterns are matched to the full path specified,
not only to the filename component.
--exclude-dir pattern
If -R is specified, it excludes directories matching the given
filename pattern from the search. Note that --exclude-dir and
--include-dir patterns are processed in the order given. If a
name matches multiple patterns, the latest matching rule wins.
If no --include-dir pattern is specified, all directories are
searched that are not excluded.
-F, --fixed-strings
Interpret pattern as a set of fixed strings (i.e., force grep to
behave as fgrep).
-f file, --file=file
Read one or more newline separated patterns from file. Empty
pattern lines match every input line. Newlines are not
considered part of a pattern. If file is empty, nothing is
matched.
-G, --basic-regexp
Interpret pattern as a basic regular expression (i.e., force grep
to behave as traditional grep).
-H Always print filename headers with output lines.
-h, --no-filename
Never print filename headers (i.e., filenames) with output lines.
--help Print a brief help message.
-I Ignore binary files. This option is equivalent to the
“--binary-files=without-match” option.
-i, --ignore-case
Perform case insensitive matching. By default, grep is case
sensitive.
--include pattern
If specified, only files matching the given filename pattern are
searched. Note that --include and --exclude patterns are
processed in the order given. If a name matches multiple
patterns, the latest matching rule wins. Patterns are matched to
the full path specified, not only to the filename component.
--include-dir pattern
If -R is specified, only directories matching the given filename
pattern are searched. Note that --include-dir and --exclude-dir
patterns are processed in the order given. If a name matches
multiple patterns, the latest matching rule wins.
-J, --bz2decompress
Decompress the bzip2(1) compressed file before looking for the
text.
-L, --files-without-match
Only the names of files not containing selected lines are written
to standard output. Pathnames are listed once per file searched.
If the standard input is searched, the string “(standard input)”
is written unless a --label is specified.
-l, --files-with-matches
Only the names of files containing selected lines are written to
standard output. grep will only search a file until a match has
been found, making searches potentially less expensive.
Pathnames are listed once per file searched. If the standard
input is searched, the string “(standard input)” is written
unless a --label is specified.
--label
Label to use in place of “(standard input)” for a file name where
a file name would normally be printed. This option applies to
-H, -L, and -l.
--mmap Use mmap(2) instead of read(2) to read input, which can result in
better performance under some circumstances but can cause
undefined behaviour.
-M, --lzma
Decompress the LZMA compressed file before looking for the text.
-m num, --max-count=num
Stop reading the file after num matches.
-n, --line-number
Each output line is preceded by its relative line number in the
file, starting at line 1. The line number counter is reset for
each file processed. This option is ignored if -c, -L, -l, or -q
is specified.
--null Prints a zero-byte after the file name.
-O If -R is specified, follow symbolic links only if they were
explicitly listed on the command line. The default is not to
follow symbolic links.
-o, --only-matching
Prints only the matching part of the lines.
-p If -R is specified, no symbolic links are followed. This is the
default.
-q, --quiet, --silent
Quiet mode: suppress normal output. grep will only search a file
until a match has been found, making searches potentially less
expensive.
-R, -r, --recursive
Recursively search subdirectories listed. (i.e., force grep to
behave as rgrep).
-S If -R is specified, all symbolic links are followed. The default
is not to follow symbolic links.
-s, --no-messages
Silent mode. Nonexistent and unreadable files are ignored (i.e.,
their error messages are suppressed).
-U, --binary
Search binary files, but do not attempt to print them.
-u This option has no effect and is provided only for compatibility
with GNU grep.
-V, --version
Display version information and exit.
-v, --invert-match
Selected lines are those not matching any of the specified
patterns.
-w, --word-regexp
The expression is searched for as a word (as if surrounded by
‘[[:<:]]’ and ‘[[:>:]]’; see re_format(7)). This option has no
effect if -x is also specified.
-x, --line-regexp
Only input lines selected against an entire fixed string or
regular expression are considered to be matching lines.
-y Equivalent to -i. Obsoleted.
-z, --null-data
Treat input and output data as sequences of lines terminated by a
zero-byte instead of a newline.
-X, --xz
Decompress the xz(1) compressed file before looking for the text.
-Z, --decompress
Force grep to behave as zgrep.
--binary-files=value
Controls searching and printing of binary files. Options are:
binary (default) Search binary files but do not print them.
without-match Do not search binary files.
text Treat all files as text.
--line-buffered
Force output to be line buffered. By default, output is line
buffered when standard output is a terminal and block buffered
otherwise.
If no file arguments are specified, the standard input is used.
Additionally, “-” may be used in place of a file name, anywhere that a
file name is accepted, to read from standard input. This includes both
-f and file arguments.
ENVIRONMENT
GREP_OPTIONS May be used to specify default options that will be placed
at the beginning of the argument list. Backslash-escaping
is not supported, unlike the behavior in GNU grep.
EXIT STATUS
The grep utility exits with one of the following values:
0 One or more lines were selected.
1 No lines were selected.
>1 An error occurred.
EXAMPLES
- Find all occurrences of the pattern ‘patricia’ in a file:
$ grep 'patricia' myfile
- Same as above but looking only for complete words:
$ grep -w 'patricia' myfile
- Count occurrences of the exact pattern ‘FOO’ :
$ grep -c FOO myfile
- Same as above but ignoring case:
$ grep -c -i FOO myfile
- Find all occurrences of the pattern ‘.Pp’ at the beginning of a line:
$ grep '^\.Pp' myfile
The apostrophes ensure the entire expression is evaluated by grep
instead of by the user's shell. The caret ‘^’ matches the null
string at the beginning of a line, and the ‘\’ escapes the ‘.’, which
would otherwise match any character.
- Find all lines in a file which do not contain the words ‘foo’ or
‘bar’:
$ grep -v -e 'foo' -e 'bar' myfile
- Peruse the file ‘calendar’ looking for either 19, 20, or 25 using
extended regular expressions:
$ egrep '19|20|25' calendar
- Show matching lines and the name of the ‘*.h’ files which contain the
pattern ‘FIXME’. Do the search recursively from the /usr/src/sys/arm
directory
$ grep -H -R FIXME --include="*.h" /usr/src/sys/arm/
- Same as above but show only the name of the matching file:
$ grep -l -R FIXME --include="*.h" /usr/src/sys/arm/
- Show lines containing the text ‘foo’. The matching part of the
output is colored and every line is prefixed with the line number and
the offset in the file for those lines that matched.
$ grep -b --colour -n foo myfile
- Show lines that match the extended regular expression patterns read
from the standard input:
$ echo -e 'Free\nBSD\nAll.*reserved' | grep -E -f - myfile
- Show lines from the output of the pciconf(8) command matching the
specified extended regular expression along with three lines of
leading context and one line of trailing context:
$ pciconf -lv | grep -B3 -A1 -E 'class.*=.*storage'
- Suppress any output and use the exit status to show an appropriate
message:
$ grep -q foo myfile && echo File matches
SEE ALSO
bzip2(1), compress(1), ed(1), ex(1), gzip(1), sed(1), xz(1), zgrep(1),
re_format(7)
STANDARDS
The grep utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The flags [-AaBbCDdGHhILmopRSUVw] are extensions to that specification,
and the behaviour of the -f flag when used with an empty pattern file is
left undefined.
All long options are provided for compatibility with GNU versions of this
utility.
Historic versions of the grep utility also supported the flags [-ruy].
This implementation supports those options; however, their use is
strongly discouraged.
HISTORY
The grep command first appeared in Version 6 AT&T UNIX.
BUGS
The grep utility does not normalize Unicode input, so a pattern
containing composed characters will not match decomposed input, and vice
versa.
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