grep, egrep,
fgrep, zgrep,
zegrep, zfgrep —
file pattern searcher
grep |
[-abcEFGHhIiLlnoqRsUVvwxZ]
[-A num]
[-B num]
[-C[num]]
[-e pattern]
[-f file]
[-m num]
[--binary-files=value]
[--context[=num]]
[--label=name]
[--line-buffered] [--null]
[pattern]
[file ...] |
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. If no file arguments are
specified, the standard input is used.
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.
The following options are available:
-A
num- Print num lines of trailing context after each
match. See also the
-B and
-C options.
-a- 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- Print num lines of leading context before each
match. See also the
-A and
-C options.
-b- Each output line is preceded by its position (in bytes) in the file. If
option
-o is also specified, the position of the
matched pattern is displayed.
-C[num],
--context[=num]- Print num lines of leading and trailing context
surrounding each match. The default is 2 and is equivalent to
-A 2
-B 2. Note: no whitespace
may be given between the option and its argument.
-c- Only a count of selected lines is written to standard output.
-E- Interpret pattern as an extended regular expression
(i.e. force
grep to behave as
egrep).
-e
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
(‘-’).
-F- Interpret pattern as a set of fixed strings (i.e.
force
grep to behave as
fgrep).
-f
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- Interpret pattern as a basic regular expression
(i.e. force
grep to behave as traditional
grep).
-H- Always print filename headers (i.e. filenames) with output lines.
-h- Never print filename headers (i.e. filenames) with output lines.
-I- Ignore binary files.
-i- Perform case insensitive matching. By default,
grep is case sensitive.
-L- 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.
-l- 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.
-m
num- Stop after finding at least one match on num
different lines.
-n- 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.
-o- Print each match, but only the match, not the entire line.
-q- Quiet mode: suppress normal output.
grep will only
search a file until a match has been found, making searches potentially
less expensive.
-R- Recursively search subdirectories listed. If no file
is given,
grep searches the current working
directory.
-s- Silent mode. Nonexistent and unreadable files are ignored (i.e. their
error messages are suppressed).
-U- Search binary files, but do not attempt to print them.
-V- Display version information. All other options are ignored.
-v- Selected lines are those
not
matching any of the specified patterns.
-w- The expression is searched for as a word (as if surrounded by
‘[[:<:]]’ and ‘[[:>:]]’; see
re_format(7)).
-x- Only input lines selected against an entire fixed string or regular
expression are considered to be matching lines.
-Z- Force
grep to behave as
zgrep.
--binary-files=value- Controls searching and printing of binary files. Options are
binary, the default: search binary files but do not
print them; without-match: do not search binary
files; and text: treat all files as text.
--label=name- Print name instead of the filename before
lines.
--line-buffered- Force output to be line buffered. By default, output is line buffered when
standard output is a terminal and block buffered otherwise.
--null- Output a zero byte instead of the character that normally follows a file
name. This option makes the output unambiguous, even in the presence of
file names containing unusual characters like newlines. This is similar to
the
-print0 primary in
find(1).
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.
To find all occurrences of the word ‘patricia’ in a
file:
$ grep 'patricia' myfile
To 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.
To find all lines in a file which do not contain the words
‘foo’ or ‘bar’:
$ grep -v -e 'foo' -e 'bar'
myfile
A simple example of an extended regular expression:
$ egrep '19|20|25'
calendar
Peruses the file ‘calendar’ looking for either 19,
20, or 25.
The grep utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The flags [-AaBbCGHhILmoRUVwZ] 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.
The grep command first appeared in
Version 4 AT&T UNIX.