1GREP(1) User Commands GREP(1)
2
6 grep, egrep, fgrep - print lines that match patterns
7
9 grep [OPTION...] PATTERNS [FILE...]
10 grep [OPTION...] -e PATTERNS ... [FILE...]
11 grep [OPTION...] -f PATTERN_FILE ... [FILE...]
12
14 grep searches for PATTERNS in each FILE. PATTERNS is one or patterns
15 separated by newline characters, and grep prints each line that matches
16 a pattern.
17 A FILE of “-” stands for standard input. If no FILE is given,
19 recursive searches examine the working directory, and nonrecursive
20 searches read standard input.
21 In addition, the variant programs egrep and fgrep are the same as
23 grep -E and grep -F, respectively. These variants are deprecated, but
24 are provided for backward compatibility.
25
27 Generic Program Information
28 --help Output a usage message and exit.
29 -V, --version
31 Output the version number of grep and exit.
32 Matcher Selection
34 -E, --extended-regexp
35 Interpret PATTERNS as extended regular expressions (EREs, see
36 below).
37 -F, --fixed-strings
39 Interpret PATTERNS as fixed strings, not regular expressions.
40 -G, --basic-regexp
42 Interpret PATTERNS as basic regular expressions (BREs, see
43 below). This is the default.
44 -P, --perl-regexp
46 Interpret PATTERNS as Perl-compatible regular expressions
47 (PCREs). This option is experimental when combined with the -z
48 (--null-data) option, and grep -P may warn of unimplemented
49 features.
50 Matching Control
52 -e PATTERNS, --regexp=PATTERNS
53 Use PATTERNS as the patterns. If this option is used multiple
54 times or is combined with the -f (--file) option, search for all
55 patterns given. This option can be used to protect a pattern
56 beginning with “-”.
57 -f FILE, --file=FILE
59 Obtain patterns from FILE, one per line. If this option is used
60 multiple times or is combined with the -e (--regexp) option,
61 search for all patterns given. The empty file contains zero
62 patterns, and therefore matches nothing.
63 -i, --ignore-case
65 Ignore case distinctions, so that characters that differ only in
66 case match each other.
67 -v, --invert-match
69 Invert the sense of matching, to select non-matching lines.
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. This option has no effect if -x is also specified.
79 -x, --line-regexp
81 Select only those matches that exactly match the whole line.
82 For a regular expression pattern, this is like parenthesizing
83 the pattern and then surrounding it with ^ and $.
84 -y Obsolete synonym for -i.
86 General Output Control
88 -c, --count
89 Suppress normal output; instead print a count of matching lines
90 for each input file. With the -v, --invert-match option (see
91 below), count non-matching lines.
92 --color[=WHEN], --colour[=WHEN]
94 Surround the matched (non-empty) strings, matching lines,
95 context lines, file names, line numbers, byte offsets, and
96 separators (for fields and groups of context lines) with escape
97 sequences to display them in color on the terminal. The colors
98 are defined by the environment variable GREP_COLORS. The
99 deprecated environment variable GREP_COLOR is still supported,
100 but its setting does not have priority. WHEN is never, always,
101 or auto.
102 -L, --files-without-match
104 Suppress normal output; instead print the name of each input
105 file from which no output would normally have been printed. The
106 scanning will stop on the first match.
107 -l, --files-with-matches
109 Suppress normal output; instead print the name of each input
110 file from which output would normally have been printed. The
111 scanning will stop on the first match.
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 -s, --no-messages
135 Suppress error messages about nonexistent or unreadable files.
136 Output Line Prefix Control
138 -b, --byte-offset
139 Print the 0-based byte offset within the input file before each
140 line of output. If -o (--only-matching) is specified, print the
141 offset of the matching part itself.
142 -H, --with-filename
144 Print the file name for each match. This is the default when
145 there is more than one file to search.
146 -h, --no-filename
148 Suppress the prefixing of file names on output. This is the
149 default when there is only one file (or only standard input) to
150 search.
151 --label=LABEL
153 Display input actually coming from standard input as input
154 coming from file LABEL. This is especially useful when
155 implementing tools like zgrep, e.g., gzip -cd foo.gz | grep
156 --label=foo -H something. See also the -H option.
157 -n, --line-number
159 Prefix each line of output with the 1-based line number within
160 its input file.
161 -T, --initial-tab
163 Make sure that the first character of actual line content lies
164 on a tab stop, so that the alignment of tabs looks normal. This
165 is useful with options that prefix their output to the actual
166 content: -H,-n, and -b. In order to improve the probability
167 that lines from a single file will all start at the same column,
168 this also causes the line number and byte offset (if present) to
169 be printed in a minimum size field width.
170 -u, --unix-byte-offsets
172 Report Unix-style byte offsets. This switch causes grep to
173 report byte offsets as if the file were a Unix-style text file,
174 i.e., with CR characters stripped off. This will produce
175 results identical to running grep on a Unix machine. This
176 option has no effect unless -b option is also used; it has no
177 effect on platforms other than MS-DOS and MS-Windows.
178 -Z, --null
180 Output a zero byte (the ASCII NUL character) instead of the
181 character that normally follows a file name. For example, grep
182 -lZ outputs a zero byte after each file name instead of the
183 usual newline. This option makes the output unambiguous, even
184 in the presence of file names containing unusual characters like
185 newlines. This option can be used with commands like find
186 -print0, perl -0, sort -z, and xargs -0 to process arbitrary
187 file names, even those that contain newline characters.
188 Context Line Control
190 -A NUM, --after-context=NUM
191 Print NUM lines of trailing context after matching lines.
192 Places a line containing a group separator (described under
193 --group-separator) between contiguous groups of matches. With
194 the -o or --only-matching option, this has no effect and a
195 warning is given.
196 -B NUM, --before-context=NUM
198 Print NUM lines of leading context before 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 -C NUM, -NUM, --context=NUM
205 Print NUM lines of output context. Places a line containing a
206 group separator (described under --group-separator) between
207 contiguous groups of matches. With the -o or --only-matching
208 option, this has no effect and a warning is given.
209 --group-separator=SEP
211 Use SEP as a group separator. By default SEP is double hyphen
212 (--).
213 --no-group-separator
215 Use empty string as a group separator.
216 File and Directory Selection
218 -a, --text
219 Process a binary file as if it were text; this is equivalent to
220 the --binary-files=text option.
221 --binary-files=TYPE
223 If a file's data or metadata indicate that the file contains
224 binary data, assume that the file is of type TYPE. Non-text
225 bytes indicate binary data; these are either output bytes that
226 are improperly encoded for the current locale, or null input
227 bytes when the -z option is not given.
228 By default, TYPE is binary, and when grep discovers that a file
230 is binary it suppresses any further output, and instead outputs
231 either a one-line message saying that a binary file matches, or
232 no message if there is no match.
233 If TYPE is without-match, when grep discovers that a file is
235 binary it assumes that the rest of the file does not match; this
236 is equivalent to the -I option.
237 If TYPE is text, grep processes a binary file as if it were
239 text; this is equivalent to the -a option.
240 When type is binary, grep may treat non-text bytes as line
242 terminators even without the -z option. This means choosing
243 binary versus text can affect whether a pattern matches a file.
244 For example, when type is binary the pattern q$ might match q
245 immediately followed by a null byte, even though this is not
246 matched when type is text. Conversely, when type is binary the
247 pattern . (period) might not match a null byte.
248 Warning: The -a option might output binary garbage, which can
250 have nasty side effects if the output is a terminal and if the
251 terminal driver interprets some of it as commands. On the other
252 hand, when reading files whose text encodings are unknown, it
253 can be helpful to use -a or to set LC_ALL='C' in the
254 environment, in order to find more matches even if the matches
255 are unsafe for direct display.
256 -D ACTION, --devices=ACTION
258 If an input file is a device, FIFO or socket, use ACTION to
259 process it. By default, ACTION is read, which means that
260 devices are read just as if they were ordinary files. If ACTION
261 is skip, devices are silently skipped.
262 -d ACTION, --directories=ACTION
264 If an input file is a directory, use ACTION to process it. By
265 default, ACTION is read, i.e., read directories just as if they
266 were ordinary files. If ACTION is skip, silently skip
267 directories. If ACTION is recurse, read all files under each
268 directory, recursively, following symbolic links only if they
269 are on the command line. This is equivalent to the -r option.
270 --exclude=GLOB
272 Skip any command-line file with a name suffix that matches the
273 pattern GLOB, using wildcard matching; a name suffix is either
274 the whole name, or any suffix starting after a / and before a
275 non-/. When searching recursively, skip any subfile whose base
276 name matches GLOB; the base name is the part after the last /.
277 A pattern can use *, ?, and [...] as wildcards, and \ to quote a
278 wildcard or backslash character literally.
279 --exclude-from=FILE
281 Skip files whose base name matches any of the file-name globs
282 read from FILE (using wildcard matching as described under
283 --exclude).
284 --exclude-dir=GLOB
286 Skip any command-line directory with a name suffix that matches
287 the pattern GLOB. When searching recursively, skip any
288 subdirectory whose base name matches GLOB. Ignore any redundant
289 trailing slashes in GLOB.
290 -I Process a binary file as if it did not contain matching data;
292 this is equivalent to the --binary-files=without-match option.
293 --include=GLOB
295 Search only files whose base name matches GLOB (using wildcard
296 matching as described under --exclude).
297 -r, --recursive
299 Read all files under each directory, recursively, following
300 symbolic links only if they are on the command line. Note that
301 if no file operand is given, grep searches the working
302 directory. This is equivalent to the -d recurse option.
303 -R, --dereference-recursive
305 Read all files under each directory, recursively. Follow all
306 symbolic links, unlike -r.
307 Other Options
309 --line-buffered
310 Use line buffering on output. This can cause a performance
311 penalty.
312 -U, --binary
314 Treat the file(s) as binary. By default, under MS-DOS and MS-
315 Windows, grep guesses whether a file is text or binary as
316 described for the --binary-files option. If grep decides the
317 file is a text file, it strips the CR characters from the
318 original file contents (to make regular expressions with ^ and $
319 work correctly). Specifying -U overrules this guesswork,
320 causing all files to be read and passed to the matching
321 mechanism verbatim; if the file is a text file with CR/LF pairs
322 at the end of each line, this will cause some regular
323 expressions to fail. This option has no effect on platforms
324 other than MS-DOS and MS-Windows.
325 -z, --null-data
327 Treat input and output data as sequences of lines, each
328 terminated by a zero byte (the ASCII NUL character) instead of a
329 newline. Like the -Z or --null option, this option can be used
330 with commands like sort -z to process arbitrary file names.
331
333 A regular expression is a pattern that describes a set of strings.
334 Regular expressions are constructed analogously to arithmetic
335 expressions, by using various operators to combine smaller expressions.
336 grep understands three different versions of regular expression syntax:
338 “basic” (BRE), “extended” (ERE) and “perl” (PCRE). In GNU grep there
339 is no difference in available functionality between basic and extended
340 syntaxes. In other implementations, basic regular expressions are less
341 powerful. The following description applies to extended regular
342 expressions; differences for basic regular expressions are summarized
343 afterwards. Perl-compatible regular expressions give additional
344 functionality, and are documented in pcresyntax(3) and pcrepattern(3),
345 but work only if PCRE is available in the system.
346 The fundamental building blocks are the regular expressions that match
348 a single character. Most characters, including all letters and digits,
349 are regular expressions that match themselves. Any meta-character with
350 special meaning may be quoted by preceding it with a backslash.
351 The period . matches any single character. It is unspecified whether
353 it matches an encoding error.
354 Character Classes and Bracket Expressions
356 A bracket expression is a list of characters enclosed by [ and ]. It
357 matches any single character in that list. If the first character of
358 the list is the caret ^ then it matches any character not in the list;
359 it is unspecified whether it matches an encoding error. For example,
360 the regular expression [0123456789] matches any single digit.
361 Within a bracket expression, a range expression consists of two
363 characters separated by a hyphen. It matches any single character that
364 sorts between the two characters, inclusive, using the locale's
365 collating sequence and character set. For example, in the default C
366 locale, [a-d] is equivalent to [abcd]. Many locales sort characters in
367 dictionary order, and in these locales [a-d] is typically not
368 equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.
369 To obtain the traditional interpretation of bracket expressions, you
370 can use the C locale by setting the LC_ALL environment variable to the
371 value C.
372 Finally, certain named classes of characters are predefined within
374 bracket expressions, as follows. Their names are self explanatory, and
375 they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:],
376 [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
377 For example, [[:alnum:]] means the character class of numbers and
378 letters in the current locale. In the C locale and ASCII character set
379 encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in
380 these class names are part of the symbolic names, and must be included
381 in addition to the brackets delimiting the bracket expression.) Most
382 meta-characters lose their special meaning inside bracket expressions.
383 To include a literal ] place it first in the list. Similarly, to
384 include a literal ^ place it anywhere but first. Finally, to include a
385 literal - place it last.
386 Anchoring
388 The caret ^ and the dollar sign $ are meta-characters that respectively
389 match the empty string at the beginning and end of a line.
390 The Backslash Character and Special Expressions
392 The symbols \< and \> respectively match the empty string at the
393 beginning and end of a word. The symbol \b matches the empty string at
394 the edge of a word, and \B matches the empty string provided it's not
395 at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and
396 \W is a synonym for [^_[:alnum:]].
397 Repetition
399 A regular expression may be followed by one of several repetition
400 operators:
401 ? The preceding item is optional and matched at most once.
402 * The preceding item will be matched zero or more times.
403 + The preceding item will be matched one or more times.
404 {n} The preceding item is matched exactly n times.
405 {n,} The preceding item is matched n or more times.
406 {,m} The preceding item is matched at most m times. This is a GNU
407 extension.
408 {n,m} The preceding item is matched at least n times, but not more
409 than m times.
410 Concatenation
412 Two regular expressions may be concatenated; the resulting regular
413 expression matches any string formed by concatenating two substrings
414 that respectively match the concatenated expressions.
415 Alternation
417 Two regular expressions may be joined by the infix operator |; the
418 resulting regular expression matches any string matching either
419 alternate expression.
420 Precedence
422 Repetition takes precedence over concatenation, which in turn takes
423 precedence over alternation. A whole expression may be enclosed in
424 parentheses to override these precedence rules and form a
425 subexpression.
426 Back References and Subexpressions
428 The back-reference \n, where n is a single digit, matches the substring
429 previously matched by the nth parenthesized subexpression of the
430 regular expression.
431 Basic vs Extended Regular Expressions
433 In basic regular expressions the meta-characters ?, +, {, |, (, and )
434 lose their special meaning; instead use the backslashed versions \?,
435 \+, \{, \|, \(, and \).
436
438 The behavior of grep is affected by the following environment
439 variables.
440 The locale for category LC_foo is specified by examining the three
442 environment variables LC_ALL, LC_foo, LANG, in that order. The first
443 of these variables that is set specifies the locale. For example, if
444 LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
445 Portuguese locale is used for the LC_MESSAGES category. The C locale
446 is used if none of these environment variables are set, if the locale
447 catalog is not installed, or if grep was not compiled with national
448 language support (NLS). The shell command locale -a lists locales that
449 are currently available.
450 GREP_OPTIONS
452 This variable specifies default options to be placed in front of
453 any explicit options. As this causes problems when writing
454 portable scripts, this feature will be removed in a future
455 release of grep, and grep warns if it is used. Please use an
456 alias or script instead.
457 GREP_COLOR
459 This variable specifies the color used to highlight matched
460 (non-empty) text. It is deprecated in favor of GREP_COLORS, but
461 still supported. The mt, ms, and mc capabilities of GREP_COLORS
462 have priority over it. It can only specify the color used to
463 highlight the matching non-empty text in any matching line (a
464 selected line when the -v command-line option is omitted, or a
465 context line when -v is specified). The default is 01;31, which
466 means a bold red foreground text on the terminal's default
467 background.
468 GREP_COLORS
470 Specifies the colors and other attributes used to highlight
471 various parts of the output. Its value is a colon-separated
472 list of capabilities that defaults to
473 ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv
474 and ne boolean capabilities omitted (i.e., false). Supported
475 capabilities are as follows.
476 sl= SGR substring for whole selected lines (i.e., matching
478 lines when the -v command-line option is omitted, or non-
479 matching lines when -v is specified). If however the
480 boolean rv capability and the -v command-line option are
481 both specified, it applies to context matching lines
482 instead. The default is empty (i.e., the terminal's
483 default color pair).
484 cx= SGR substring for whole context lines (i.e., non-matching
486 lines when the -v command-line option is omitted, or
487 matching lines when -v is specified). If however the
488 boolean rv capability and the -v command-line option are
489 both specified, it applies to selected non-matching lines
490 instead. The default is empty (i.e., the terminal's
491 default color pair).
492 rv Boolean value that reverses (swaps) the meanings of the
494 sl= and cx= capabilities when the -v command-line option
495 is specified. The default is false (i.e., the capability
496 is omitted).
497 mt=01;31
499 SGR substring for matching non-empty text in any matching
500 line (i.e., a selected line when the -v command-line
501 option is omitted, or a context line when -v is
502 specified). Setting this is equivalent to setting both
503 ms= and mc= at once to the same value. The default is a
504 bold red text foreground over the current line
505 background.
506 ms=01;31
508 SGR substring for matching non-empty text in a selected
509 line. (This is only used when the -v command-line option
510 is omitted.) The effect of the sl= (or cx= if rv)
511 capability remains active when this kicks in. The
512 default is a bold red text foreground over the current
513 line background.
514 mc=01;31
516 SGR substring for matching non-empty text in a context
517 line. (This is only used when the -v command-line option
518 is specified.) The effect of the cx= (or sl= if rv)
519 capability remains active when this kicks in. The
520 default is a bold red text foreground over the current
521 line background.
522 fn=35 SGR substring for file names prefixing any content line.
524 The default is a magenta text foreground over the
525 terminal's default background.
526 ln=32 SGR substring for line numbers prefixing any content
528 line. The default is a green text foreground over the
529 terminal's default background.
530 bn=32 SGR substring for byte offsets prefixing any content
532 line. The default is a green text foreground over the
533 terminal's default background.
534 se=36 SGR substring for separators that are inserted between
536 selected line fields (:), between context line fields,
537 (-), and between groups of adjacent lines when nonzero
538 context is specified (--). The default is a cyan text
539 foreground over the terminal's default background.
540 ne Boolean value that prevents clearing to the end of line
542 using Erase in Line (EL) to Right (\33[K) each time a
543 colorized item ends. This is needed on terminals on
544 which EL is not supported. It is otherwise useful on
545 terminals for which the back_color_erase (bce) boolean
546 terminfo capability does not apply, when the chosen
547 highlight colors do not affect the background, or when EL
548 is too slow or causes too much flicker. The default is
549 false (i.e., the capability is omitted).
550 Note that boolean capabilities have no =... part. They are
552 omitted (i.e., false) by default and become true when specified.
553 See the Select Graphic Rendition (SGR) section in the
555 documentation of the text terminal that is used for permitted
556 values and their meaning as character attributes. These
557 substring values are integers in decimal representation and can
558 be concatenated with semicolons. grep takes care of assembling
559 the result into a complete SGR sequence (\33[...m). Common
560 values to concatenate include 1 for bold, 4 for underline, 5 for
561 blink, 7 for inverse, 39 for default foreground color, 30 to 37
562 for foreground colors, 90 to 97 for 16-color mode foreground
563 colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
564 foreground colors, 49 for default background color, 40 to 47 for
565 background colors, 100 to 107 for 16-color mode background
566 colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
567 background colors.
568 LC_ALL, LC_COLLATE, LANG
570 These variables specify the locale for the LC_COLLATE category,
571 which determines the collating sequence used to interpret range
572 expressions like [a-z].
573 LC_ALL, LC_CTYPE, LANG
575 These variables specify the locale for the LC_CTYPE category,
576 which determines the type of characters, e.g., which characters
577 are whitespace. This category also determines the character
578 encoding, that is, whether text is encoded in UTF-8, ASCII, or
579 some other encoding. In the C or POSIX locale, all characters
580 are encoded as a single byte and every byte is a valid
581 character.
582 LC_ALL, LC_MESSAGES, LANG
584 These variables specify the locale for the LC_MESSAGES category,
585 which determines the language that grep uses for messages. The
586 default C locale uses American English messages.
587 POSIXLY_CORRECT
589 If set, grep behaves as POSIX requires; otherwise, grep behaves
590 more like other GNU programs. POSIX requires that options that
591 follow file names must be treated as file names; by default,
592 such options are permuted to the front of the operand list and
593 are treated as options. Also, POSIX requires that unrecognized
594 options be diagnosed as “illegal”, but since they are not really
595 against the law the default is to diagnose them as “invalid”.
596 POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
597 described below.
598 _N_GNU_nonoption_argv_flags_
600 (Here N is grep's numeric process ID.) If the ith character of
601 this environment variable's value is 1, do not consider the ith
602 operand of grep to be an option, even if it appears to be one.
603 A shell can put this variable in the environment for each
604 command it runs, specifying which operands are the results of
605 file name wildcard expansion and therefore should not be treated
606 as options. This behavior is available only with the GNU C
607 library, and only when POSIXLY_CORRECT is not set.
608
610 Normally the exit status is 0 if a line is selected, 1 if no lines were
611 selected, and 2 if an error occurred. However, if the -q or --quiet or
612 --silent is used and a line is selected, the exit status is 0 even if
613 an error occurred.
614
616 Copyright 1998–2000, 2002, 2005–2018 Free Software Foundation, Inc.
617 This is free software; see the source for copying conditions. There is
619 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
620 PURPOSE.
621
623 Reporting Bugs
624 Email bug reports to the bug-reporting address ⟨bug-grep@gnu.org⟩. An
625 email archive ⟨https://lists.gnu.org/mailman/listinfo/bug-grep⟩ and a
626 bug tracker ⟨https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep⟩
627 are available.
628 Known Bugs
630 Large repetition counts in the {n,m} construct may cause grep to use
631 lots of memory. In addition, certain other obscure regular expressions
632 require exponential time and space, and may cause grep to run out of
633 memory.
634 Back-references are very slow, and may require exponential time.
636
638 Regular Manual Pages
639 awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1),
640 xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3),
641 terminfo(5), glob(7), regex(7).
642 POSIX Programmer's Manual Page
644 grep(1p).
645 Full Documentation
647 A complete manual ⟨https://www.gnu.org/software/grep/manual/⟩ is avail‐
648 able. If the info and grep programs are properly installed at your
649 site, the command
650 info grep
652 should give you access to the complete manual.
654
656 This man page is maintained only fitfully; the full documentation is
657 often more up-to-date.
658GNU grep 3.3 2018-05-11 GREP(1)