1GREP(1) General Commands Manual GREP(1)
2
6 grep, egrep, fgrep - print lines matching a pattern
7
9 grep [OPTIONS] PATTERN [FILE...]
10 grep [OPTIONS] [-e PATTERN | -f FILE] [FILE...]
11
13 grep searches the named input FILEs (or standard input if no files are
14 named, or if a single hyphen-minus (-) is given as file name) for lines
15 containing a match to the given PATTERN. By default, grep prints the
16 matching lines.
17 In addition, two variant programs egrep and fgrep are available. egrep
19 is the same as grep -E. fgrep is the same as grep -F. Direct
20 invocation as either egrep or fgrep is deprecated, but is provided to
21 allow historical applications that rely on them to run unmodified.
22
24 Generic Program Information
25 --help Print a usage message briefly summarizing these command-line
26 options and the bug-reporting address, then exit.
27 -V, --version
29 Print the version number of grep to the standard output stream.
30 This version number should be included in all bug reports (see
31 below).
32 Matcher Selection
34 -E, --extended-regexp
35 Interpret PATTERN as an extended regular expression (ERE, see
36 below). (-E is specified by POSIX.)
37 -F, --fixed-strings, --fixed-regexp
39 Interpret PATTERN as a list of fixed strings, separated by
40 newlines, any of which is to be matched. (-F is specified by
41 POSIX, --fixed-regexp is an obsoleted alias, please do not use
42 it in new scripts.)
43 -G, --basic-regexp
45 Interpret PATTERN as a basic regular expression (BRE, see
46 below). This is the default.
47 -P, --perl-regexp
49 Interpret PATTERN as a Perl regular expression. This is highly
50 experimental and grep -P may warn of unimplemented features.
51 Matching Control
53 -e PATTERN, --regexp=PATTERN
54 Use PATTERN as the pattern. This can be used to specify
55 multiple search patterns, or to protect a pattern beginning with
56 a hyphen (-). (-e is specified by POSIX.)
57 -f FILE, --file=FILE
59 Obtain patterns from FILE, one per line. The empty file
60 contains zero patterns, and therefore matches nothing. (-f is
61 specified by POSIX.)
62 -i, --ignore-case
64 Ignore case distinctions in both the PATTERN and the input
65 files. (-i is specified by POSIX.)
66 -v, --invert-match
68 Invert the sense of matching, to select non-matching lines. (-v
69 is specified by POSIX.)
70 -w, --word-regexp
72 Select only those lines containing matches that form whole
73 words. The test is that the matching substring must either be
74 at the beginning of the line, or preceded by a non-word
75 constituent character. Similarly, it must be either at the end
76 of the line or followed by a non-word constituent character.
77 Word-constituent characters are letters, digits, and the
78 underscore.
79 -x, --line-regexp
81 Select only those matches that exactly match the whole line.
82 (-x is specified by POSIX.)
83 -y Obsolete synonym for -i.
85 General Output Control
87 -c, --count
88 Suppress normal output; instead print a count of matching lines
89 for each input file. With the -v, --invert-match option (see
90 below), count non-matching lines. (-c is specified by POSIX.)
91 --color[=WHEN], --colour[=WHEN]
93 Surround the matched (non-empty) strings, matching lines,
94 context lines, file names, line numbers, byte offsets, and
95 separators (for fields and groups of context lines) with escape
96 sequences to display them in color on the terminal. The colors
97 are defined by the environment variable GREP_COLORS. The
98 deprecated environment variable GREP_COLOR is still supported,
99 but its setting does not have priority. WHEN is never, always,
100 or auto.
101 -L, --files-without-match
103 Suppress normal output; instead print the name of each input
104 file from which no output would normally have been printed. The
105 scanning will stop on the first match.
106 -l, --files-with-matches
108 Suppress normal output; instead print the name of each input
109 file from which output would normally have been printed. The
110 scanning will stop on the first match. (-l is specified by
111 POSIX.)
112 -m NUM, --max-count=NUM
114 Stop reading a file after NUM matching lines. If the input is
115 standard input from a regular file, and NUM matching lines are
116 output, grep ensures that the standard input is positioned to
117 just after the last matching line before exiting, regardless of
118 the presence of trailing context lines. This enables a calling
119 process to resume a search. When grep stops after NUM matching
120 lines, it outputs any trailing context lines. When the -c or
121 --count option is also used, grep does not output a count
122 greater than NUM. When the -v or --invert-match option is also
123 used, grep stops after outputting NUM non-matching lines.
124 -o, --only-matching
126 Print only the matched (non-empty) parts of a matching line,
127 with each such part on a separate output line.
128 -q, --quiet, --silent
130 Quiet; do not write anything to standard output. Exit
131 immediately with zero status if any match is found, even if an
132 error was detected. Also see the -s or --no-messages option.
133 (-q is specified by POSIX.)
134 -s, --no-messages
136 Suppress error messages about nonexistent or unreadable files.
137 Portability note: unlike GNU grep, 7th Edition Unix grep did not
138 conform to POSIX, because it lacked -q and its -s option behaved
139 like GNU grep's -q option. USG-style grep also lacked -q but
140 its -s option behaved like GNU grep. Portable shell scripts
141 should avoid both -q and -s and should redirect standard and
142 error output to /dev/null instead. (-s is specified by POSIX.)
143 Output Line Prefix Control
145 -b, --byte-offset
146 Print the 0-based byte offset within the input file before each
147 line of output. If -o (--only-matching) is specified, print the
148 offset of the matching part itself.
149 -H, --with-filename
151 Print the file name for each match. This is the default when
152 there is more than one file to search.
153 -h, --no-filename
155 Suppress the prefixing of file names on output. This is the
156 default when there is only one file (or only standard input) to
157 search.
158 --label=LABEL
160 Display input actually coming from standard input as input
161 coming from file LABEL. This is especially useful when
162 implementing tools like zgrep, e.g., gzip -cd foo.gz | grep
163 --label=foo -H something. See also the -H option.
164 -n, --line-number
166 Prefix each line of output with the 1-based line number within
167 its input file. (-n is specified by POSIX.)
168 -T, --initial-tab
170 Make sure that the first character of actual line content lies
171 on a tab stop, so that the alignment of tabs looks normal. This
172 is useful with options that prefix their output to the actual
173 content: -H,-n, and -b. In order to improve the probability
174 that lines from a single file will all start at the same column,
175 this also causes the line number and byte offset (if present) to
176 be printed in a minimum size field width.
177 -u, --unix-byte-offsets
179 Report Unix-style byte offsets. This switch causes grep to
180 report byte offsets as if the file were a Unix-style text file,
181 i.e., with CR characters stripped off. This will produce
182 results identical to running grep on a Unix machine. This
183 option has no effect unless -b option is also used; it has no
184 effect on platforms other than MS-DOS and MS-Windows.
185 -Z, --null
187 Output a zero byte (the ASCII NUL character) instead of the
188 character that normally follows a file name. For example, grep
189 -lZ outputs a zero byte after each file name instead of the
190 usual newline. This option makes the output unambiguous, even
191 in the presence of file names containing unusual characters like
192 newlines. This option can be used with commands like find
193 -print0, perl -0, sort -z, and xargs -0 to process arbitrary
194 file names, even those that contain newline characters.
195 Context Line Control
197 -A NUM, --after-context=NUM
198 Print NUM lines of trailing context after matching lines.
199 Places a line containing a group separator (described under
200 --group-separator) between contiguous groups of matches. With
201 the -o or --only-matching option, this has no effect and a
202 warning is given.
203 -B NUM, --before-context=NUM
205 Print NUM lines of leading context before matching lines.
206 Places a line containing a group separator (described under
207 --group-separator) between contiguous groups of matches. With
208 the -o or --only-matching option, this has no effect and a
209 warning is given.
210 -C NUM, -NUM, --context=NUM
212 Print NUM lines of output context. Places a line containing a
213 group separator (described under --group-separator) between
214 contiguous groups of matches. With the -o or --only-matching
215 option, this has no effect and a warning is given.
216 --group-separator=SEP
218 Use SEP as a group separator. By default SEP is double hyphen
219 (--).
220 --no-group-separator
222 Use empty string as a group separator.
223 File and Directory Selection
225 -a, --text
226 Process a binary file as if it were text; this is equivalent to
227 the --binary-files=text option.
228 --binary-files=TYPE
230 If the first few bytes of a file indicate that the file contains
231 binary data, assume that the file is of type TYPE. By default,
232 TYPE is binary, and grep normally outputs either a one-line
233 message saying that a binary file matches, or no message if
234 there is no match. If TYPE is without-match, grep assumes that
235 a binary file does not match; this is equivalent to the -I
236 option. If TYPE is text, grep processes a binary file as if it
237 were text; this is equivalent to the -a option. Warning: grep
238 --binary-files=text might output binary garbage, which can have
239 nasty side effects if the output is a terminal and if the
240 terminal driver interprets some of it as commands.
241 -D ACTION, --devices=ACTION
243 If an input file is a device, FIFO or socket, use ACTION to
244 process it. By default, ACTION is read, which means that
245 devices are read just as if they were ordinary files. If ACTION
246 is skip, devices are silently skipped.
247 -d ACTION, --directories=ACTION
249 If an input file is a directory, use ACTION to process it. By
250 default, ACTION is read, i.e., read directories just as if they
251 were ordinary files. If ACTION is skip, silently skip
252 directories. If ACTION is recurse, read all files under each
253 directory, recursively, following symbolic links only if they
254 are on the command line. This is equivalent to the -r option.
255 --exclude=GLOB
257 Skip files whose base name matches GLOB (using wildcard
258 matching). A file-name glob can use *, ?, and [...] as
259 wildcards, and \ to quote a wildcard or backslash character
260 literally.
261 --exclude-from=FILE
263 Skip files whose base name matches any of the file-name globs
264 read from FILE (using wildcard matching as described under
265 --exclude).
266 --exclude-dir=DIR
268 Exclude directories matching the pattern DIR from recursive
269 searches.
270 -I Process a binary file as if it did not contain matching data;
272 this is equivalent to the --binary-files=without-match option.
273 --include=GLOB
275 Search only files whose base name matches GLOB (using wildcard
276 matching as described under --exclude).
277 -r, --recursive
279 Read all files under each directory, recursively, following
280 symbolic links only if they are on the command line. This is
281 equivalent to the -d recurse option.
282 -R, --dereference-recursive
284 Read all files under each directory, recursively. Follow all
285 symbolic links, unlike -r.
286 Other Options
288 --line-buffered
289 Use line buffering on output. This can cause a performance
290 penalty.
291 -U, --binary
293 Treat the file(s) as binary. By default, under MS-DOS and MS-
294 Windows, grep guesses the file type by looking at the contents
295 of the first 32KB read from the file. If grep decides the file
296 is a text file, it strips the CR characters from the original
297 file contents (to make regular expressions with ^ and $ work
298 correctly). Specifying -U overrules this guesswork, causing all
299 files to be read and passed to the matching mechanism verbatim;
300 if the file is a text file with CR/LF pairs at the end of each
301 line, this will cause some regular expressions to fail. This
302 option has no effect on platforms other than MS-DOS and MS-
303 Windows.
304 -z, --null-data
306 Treat the input as a set of lines, each terminated by a zero
307 byte (the ASCII NUL character) instead of a newline. Like the
308 -Z or --null option, this option can be used with commands like
309 sort -z to process arbitrary file names.
310
312 A regular expression is a pattern that describes a set of strings.
313 Regular expressions are constructed analogously to arithmetic
314 expressions, by using various operators to combine smaller expressions.
315 grep understands three different versions of regular expression syntax:
317 “basic,” “extended” and “perl.” In GNU grep, there is no difference in
318 available functionality between basic and extended syntaxes. In other
319 implementations, basic regular expressions are less powerful. The
320 following description applies to extended regular expressions;
321 differences for basic regular expressions are summarized afterwards.
322 Perl regular expressions give additional functionality, and are
323 documented in pcresyntax(3) and pcrepattern(3), but may not be
324 available on every system.
325 The fundamental building blocks are the regular expressions that match
327 a single character. Most characters, including all letters and digits,
328 are regular expressions that match themselves. Any meta-character with
329 special meaning may be quoted by preceding it with a backslash.
330 The period . matches any single character.
332 Character Classes and Bracket Expressions
334 A bracket expression is a list of characters enclosed by [ and ]. It
335 matches any single character in that list; if the first character of
336 the list is the caret ^ then it matches any character not in the list.
337 For example, the regular expression [0123456789] matches any single
338 digit.
339 Within a bracket expression, a range expression consists of two
341 characters separated by a hyphen. It matches any single character that
342 sorts between the two characters, inclusive, using the locale's
343 collating sequence and character set. For example, in the default C
344 locale, [a-d] is equivalent to [abcd]. Many locales sort characters in
345 dictionary order, and in these locales [a-d] is typically not
346 equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.
347 To obtain the traditional interpretation of bracket expressions, you
348 can use the C locale by setting the LC_ALL environment variable to the
349 value C.
350 Finally, certain named classes of characters are predefined within
352 bracket expressions, as follows. Their names are self explanatory, and
353 they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:],
354 [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
355 For example, [[:alnum:]] means the character class of numbers and
356 letters in the current locale. In the C locale and ASCII character set
357 encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in
358 these class names are part of the symbolic names, and must be included
359 in addition to the brackets delimiting the bracket expression.) Most
360 meta-characters lose their special meaning inside bracket expressions.
361 To include a literal ] place it first in the list. Similarly, to
362 include a literal ^ place it anywhere but first. Finally, to include a
363 literal - place it last.
364 Anchoring
366 The caret ^ and the dollar sign $ are meta-characters that respectively
367 match the empty string at the beginning and end of a line.
368 The Backslash Character and Special Expressions
370 The symbols \< and \> respectively match the empty string at the
371 beginning and end of a word. The symbol \b matches the empty string at
372 the edge of a word, and \B matches the empty string provided it's not
373 at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and
374 \W is a synonym for [^_[:alnum:]].
375 Repetition
377 A regular expression may be followed by one of several repetition
378 operators:
379 ? The preceding item is optional and matched at most once.
380 * The preceding item will be matched zero or more times.
381 + The preceding item will be matched one or more times.
382 {n} The preceding item is matched exactly n times.
383 {n,} The preceding item is matched n or more times.
384 {,m} The preceding item is matched at most m times. This is a GNU
385 extension.
386 {n,m} The preceding item is matched at least n times, but not more
387 than m times.
388 Concatenation
390 Two regular expressions may be concatenated; the resulting regular
391 expression matches any string formed by concatenating two substrings
392 that respectively match the concatenated expressions.
393 Alternation
395 Two regular expressions may be joined by the infix operator |; the
396 resulting regular expression matches any string matching either
397 alternate expression.
398 Precedence
400 Repetition takes precedence over concatenation, which in turn takes
401 precedence over alternation. A whole expression may be enclosed in
402 parentheses to override these precedence rules and form a
403 subexpression.
404 Back References and Subexpressions
406 The back-reference \n, where n is a single digit, matches the substring
407 previously matched by the nth parenthesized subexpression of the
408 regular expression.
409 Basic vs Extended Regular Expressions
411 In basic regular expressions the meta-characters ?, +, {, |, (, and )
412 lose their special meaning; instead use the backslashed versions \?,
413 \+, \{, \|, \(, and \).
414 Traditional egrep did not support the { meta-character, and some egrep
416 implementations support \{ instead, so portable scripts should avoid {
417 in grep -E patterns and should use [{] to match a literal {.
418 GNU grep -E attempts to support traditional usage by assuming that { is
420 not special if it would be the start of an invalid interval
421 specification. For example, the command grep -E '{1' searches for the
422 two-character string {1 instead of reporting a syntax error in the
423 regular expression. POSIX allows this behavior as an extension, but
424 portable scripts should avoid it.
425
427 The behavior of grep is affected by the following environment
428 variables.
429 The locale for category LC_foo is specified by examining the three
431 environment variables LC_ALL, LC_foo, LANG, in that order. The first
432 of these variables that is set specifies the locale. For example, if
433 LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
434 Portuguese locale is used for the LC_MESSAGES category. The C locale
435 is used if none of these environment variables are set, if the locale
436 catalog is not installed, or if grep was not compiled with national
437 language support (NLS).
438 GREP_OPTIONS
440 This variable specifies default options to be placed in front of
441 any explicit options. For example, if GREP_OPTIONS is
442 '--binary-files=without-match --directories=skip', grep behaves
443 as if the two options --binary-files=without-match and
444 --directories=skip had been specified before any explicit
445 options. Option specifications are separated by whitespace. A
446 backslash escapes the next character, so it can be used to
447 specify an option containing whitespace or a backslash.
448 GREP_COLOR
450 This variable specifies the color used to highlight matched
451 (non-empty) text. It is deprecated in favor of GREP_COLORS, but
452 still supported. The mt, ms, and mc capabilities of GREP_COLORS
453 have priority over it. It can only specify the color used to
454 highlight the matching non-empty text in any matching line (a
455 selected line when the -v command-line option is omitted, or a
456 context line when -v is specified). The default is 01;31, which
457 means a bold red foreground text on the terminal's default
458 background.
459 GREP_COLORS
461 Specifies the colors and other attributes used to highlight
462 various parts of the output. Its value is a colon-separated
463 list of capabilities that defaults to
464 ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv
465 and ne boolean capabilities omitted (i.e., false). Supported
466 capabilities are as follows.
467 sl= SGR substring for whole selected lines (i.e., matching
469 lines when the -v command-line option is omitted, or non-
470 matching lines when -v is specified). If however the
471 boolean rv capability and the -v command-line option are
472 both specified, it applies to context matching lines
473 instead. The default is empty (i.e., the terminal's
474 default color pair).
475 cx= SGR substring for whole context lines (i.e., non-matching
477 lines when the -v command-line option is omitted, or
478 matching lines when -v is specified). If however the
479 boolean rv capability and the -v command-line option are
480 both specified, it applies to selected non-matching lines
481 instead. The default is empty (i.e., the terminal's
482 default color pair).
483 rv Boolean value that reverses (swaps) the meanings of the
485 sl= and cx= capabilities when the -v command-line option
486 is specified. The default is false (i.e., the capability
487 is omitted).
488 mt=01;31
490 SGR substring for matching non-empty text in any matching
491 line (i.e., a selected line when the -v command-line
492 option is omitted, or a context line when -v is
493 specified). Setting this is equivalent to setting both
494 ms= and mc= at once to the same value. The default is a
495 bold red text foreground over the current line
496 background.
497 ms=01;31
499 SGR substring for matching non-empty text in a selected
500 line. (This is only used when the -v command-line option
501 is omitted.) The effect of the sl= (or cx= if rv)
502 capability remains active when this kicks in. The
503 default is a bold red text foreground over the current
504 line background.
505 mc=01;31
507 SGR substring for matching non-empty text in a context
508 line. (This is only used when the -v command-line option
509 is specified.) The effect of the cx= (or sl= if rv)
510 capability remains active when this kicks in. The
511 default is a bold red text foreground over the current
512 line background.
513 fn=35 SGR substring for file names prefixing any content line.
515 The default is a magenta text foreground over the
516 terminal's default background.
517 ln=32 SGR substring for line numbers prefixing any content
519 line. The default is a green text foreground over the
520 terminal's default background.
521 bn=32 SGR substring for byte offsets prefixing any content
523 line. The default is a green text foreground over the
524 terminal's default background.
525 se=36 SGR substring for separators that are inserted between
527 selected line fields (:), between context line fields,
528 (-), and between groups of adjacent lines when nonzero
529 context is specified (--). The default is a cyan text
530 foreground over the terminal's default background.
531 ne Boolean value that prevents clearing to the end of line
533 using Erase in Line (EL) to Right (\33[K) each time a
534 colorized item ends. This is needed on terminals on
535 which EL is not supported. It is otherwise useful on
536 terminals for which the back_color_erase (bce) boolean
537 terminfo capability does not apply, when the chosen
538 highlight colors do not affect the background, or when EL
539 is too slow or causes too much flicker. The default is
540 false (i.e., the capability is omitted).
541 Note that boolean capabilities have no =... part. They are
543 omitted (i.e., false) by default and become true when specified.
544 See the Select Graphic Rendition (SGR) section in the
546 documentation of the text terminal that is used for permitted
547 values and their meaning as character attributes. These
548 substring values are integers in decimal representation and can
549 be concatenated with semicolons. grep takes care of assembling
550 the result into a complete SGR sequence (\33[...m). Common
551 values to concatenate include 1 for bold, 4 for underline, 5 for
552 blink, 7 for inverse, 39 for default foreground color, 30 to 37
553 for foreground colors, 90 to 97 for 16-color mode foreground
554 colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
555 foreground colors, 49 for default background color, 40 to 47 for
556 background colors, 100 to 107 for 16-color mode background
557 colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
558 background colors.
559 LC_ALL, LC_COLLATE, LANG
561 These variables specify the locale for the LC_COLLATE category,
562 which determines the collating sequence used to interpret range
563 expressions like [a-z].
564 LC_ALL, LC_CTYPE, LANG
566 These variables specify the locale for the LC_CTYPE category,
567 which determines the type of characters, e.g., which characters
568 are whitespace.
569 LC_ALL, LC_MESSAGES, LANG
571 These variables specify the locale for the LC_MESSAGES category,
572 which determines the language that grep uses for messages. The
573 default C locale uses American English messages.
574 POSIXLY_CORRECT
576 If set, grep behaves as POSIX requires; otherwise, grep behaves
577 more like other GNU programs. POSIX requires that options that
578 follow file names must be treated as file names; by default,
579 such options are permuted to the front of the operand list and
580 are treated as options. Also, POSIX requires that unrecognized
581 options be diagnosed as “illegal”, but since they are not really
582 against the law the default is to diagnose them as “invalid”.
583 POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
584 described below.
585 _N_GNU_nonoption_argv_flags_
587 (Here N is grep's numeric process ID.) If the ith character of
588 this environment variable's value is 1, do not consider the ith
589 operand of grep to be an option, even if it appears to be one.
590 A shell can put this variable in the environment for each
591 command it runs, specifying which operands are the results of
592 file name wildcard expansion and therefore should not be treated
593 as options. This behavior is available only with the GNU C
594 library, and only when POSIXLY_CORRECT is not set.
595
597 Normally, the exit status is 0 if selected lines are found and 1
598 otherwise. But the exit status is 2 if an error occurred, unless the
599 -q or --quiet or --silent option is used and a selected line is found.
600 Note, however, that POSIX only mandates, for programs such as grep,
601 cmp, and diff, that the exit status in case of error be greater than 1;
602 it is therefore advisable, for the sake of portability, to use logic
603 that tests for this general condition instead of strict equality
604 with 2.
605
607 Copyright 1998-2000, 2002, 2005-2014 Free Software Foundation, Inc.
608 This is free software; see the source for copying conditions. There is
610 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
611 PURPOSE.
612
614 Reporting Bugs
615 Email bug reports to <bug-grep@gnu.org>, a mailing list whose web page
616 is <http://lists.gnu.org/mailman/listinfo/bug-grep>. grep's Savannah
617 bug tracker is located at <http://savannah.gnu.org/bugs/?group=grep>.
618 Known Bugs
620 Large repetition counts in the {n,m} construct may cause grep to use
621 lots of memory. In addition, certain other obscure regular expressions
622 require exponential time and space, and may cause grep to run out of
623 memory.
624 Back-references are very slow, and may require exponential time.
626
628 Regular Manual Pages
629 awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1),
630 xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3),
631 terminfo(5), glob(7), regex(7).
632 POSIX Programmer's Manual Page
634 grep(1p).
635 TeXinfo Documentation
637 The full documentation for grep is maintained as a TeXinfo manual,
638 which you can read at http://www.gnu.org/software/grep/manual/. If the
639 info and grep programs are properly installed at your site, the command
640 info grep
642 should give you access to the complete manual.
644
646 This man page is maintained only fitfully; the full documentation is
647 often more up-to-date.
648 GNU's not Unix, but Unix is a beast; its plural form is Unixen.
650User Commands GNU grep 2.20 GREP(1)