1GREP(1) User Commands GREP(1)
2
6 grep - 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 more
15 patterns separated by newline characters, and grep prints each line
16 that matches a pattern. Typically PATTERNS should be quoted when grep
17 is used in a shell command.
18 A FILE of “-” stands for standard input. If no FILE is given,
20 recursive searches examine the working directory, and nonrecursive
21 searches read standard input.
22
24 Generic Program Information
25 --help Output a usage message and exit.
26 -V, --version
28 Output the version number of grep and exit.
29 Pattern Syntax
31 -E, --extended-regexp
32 Interpret PATTERNS as extended regular expressions (EREs, see
33 below).
34 -F, --fixed-strings
36 Interpret PATTERNS as fixed strings, not regular expressions.
37 -G, --basic-regexp
39 Interpret PATTERNS as basic regular expressions (BREs, see
40 below). This is the default.
41 -P, --perl-regexp
43 Interpret PATTERNS as Perl-compatible regular expressions
44 (PCREs). This option is experimental when combined with the -z
45 (--null-data) option, and grep -P may warn of unimplemented
46 features.
47 Matching Control
49 -e PATTERNS, --regexp=PATTERNS
50 Use PATTERNS as the patterns. If this option is used multiple
51 times or is combined with the -f (--file) option, search for all
52 patterns given. This option can be used to protect a pattern
53 beginning with “-”.
54 -f FILE, --file=FILE
56 Obtain patterns from FILE, one per line. If this option is used
57 multiple times or is combined with the -e (--regexp) option,
58 search for all patterns given. The empty file contains zero
59 patterns, and therefore matches nothing.
60 -i, --ignore-case
62 Ignore case distinctions in patterns and input data, so that
63 characters that differ only in case match each other.
64 --no-ignore-case
66 Do not ignore case distinctions in patterns and input data.
67 This is the default. This option is useful for passing to shell
68 scripts that already use -i, to cancel its effects because the
69 two options override each other.
70 -v, --invert-match
72 Invert the sense of matching, to select non-matching lines.
73 -w, --word-regexp
75 Select only those lines containing matches that form whole
76 words. The test is that the matching substring must either be
77 at the beginning of the line, or preceded by a non-word
78 constituent character. Similarly, it must be either at the end
79 of the line or followed by a non-word constituent character.
80 Word-constituent characters are letters, digits, and the
81 underscore. This option has no effect if -x is also specified.
82 -x, --line-regexp
84 Select only those matches that exactly match the whole line.
85 For a regular expression pattern, this is like parenthesizing
86 the pattern and then surrounding it with ^ and $.
87 General Output Control
89 -c, --count
90 Suppress normal output; instead print a count of matching lines
91 for each input file. With the -v, --invert-match option (see
92 above), count non-matching lines.
93 --color[=WHEN], --colour[=WHEN]
95 Surround the matched (non-empty) strings, matching lines,
96 context lines, file names, line numbers, byte offsets, and
97 separators (for fields and groups of context lines) with escape
98 sequences to display them in color on the terminal. The colors
99 are defined by the environment variable GREP_COLORS. WHEN is
100 never, always, 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.
105 -l, --files-with-matches
107 Suppress normal output; instead print the name of each input
108 file from which output would normally have been printed.
109 Scanning each input file stops upon first match.
110 -m NUM, --max-count=NUM
112 Stop reading a file after NUM matching lines. If NUM is zero,
113 grep stops right away without reading input. A NUM of -1 is
114 treated as infinity and grep does not stop; this is the default.
115 If the input is standard input from a regular file, and NUM
116 matching lines are output, grep ensures that the standard input
117 is positioned to just after the last matching line before
118 exiting, regardless of the presence of trailing context lines.
119 This enables a calling process to resume a search. When grep
120 stops after NUM matching lines, it outputs any trailing context
121 lines. When the -c or --count option is also used, grep does
122 not output a count greater than NUM. When the -v or
123 --invert-match option is also used, grep stops after outputting
124 NUM non-matching lines.
125 -o, --only-matching
127 Print only the matched (non-empty) parts of a matching line,
128 with each such part on a separate output line.
129 -q, --quiet, --silent
131 Quiet; do not write anything to standard output. Exit
132 immediately with zero status if any match is found, even if an
133 error was detected. Also see the -s or --no-messages option.
134 -s, --no-messages
136 Suppress error messages about nonexistent or unreadable files.
137 Output Line Prefix Control
139 -b, --byte-offset
140 Print the 0-based byte offset within the input file before each
141 line of output. If -o (--only-matching) is specified, print the
142 offset of the matching part itself.
143 -H, --with-filename
145 Print the file name for each match. This is the default when
146 there is more than one file to search. This is a GNU extension.
147 -h, --no-filename
149 Suppress the prefixing of file names on output. This is the
150 default when there is only one file (or only standard input) to
151 search.
152 --label=LABEL
154 Display input actually coming from standard input as input
155 coming from file LABEL. This can be useful for commands that
156 transform a file's contents before searching, e.g., gzip -cd
157 foo.gz | grep --label=foo -H 'some pattern'. See also the -H
158 option.
159 -n, --line-number
161 Prefix each line of output with the 1-based line number within
162 its input file.
163 -T, --initial-tab
165 Make sure that the first character of actual line content lies
166 on a tab stop, so that the alignment of tabs looks normal. This
167 is useful with options that prefix their output to the actual
168 content: -H,-n, and -b. In order to improve the probability
169 that lines from a single file will all start at the same column,
170 this also causes the line number and byte offset (if present) to
171 be printed in a minimum size field width.
172 -Z, --null
174 Output a zero byte (the ASCII NUL character) instead of the
175 character that normally follows a file name. For example, grep
176 -lZ outputs a zero byte after each file name instead of the
177 usual newline. This option makes the output unambiguous, even
178 in the presence of file names containing unusual characters like
179 newlines. This option can be used with commands like find
180 -print0, perl -0, sort -z, and xargs -0 to process arbitrary
181 file names, even those that contain newline characters.
182 Context Line Control
184 -A NUM, --after-context=NUM
185 Print NUM lines of trailing context after matching lines.
186 Places a line containing a group separator (--) between
187 contiguous groups of matches. With the -o or --only-matching
188 option, this has no effect and a warning is given.
189 -B NUM, --before-context=NUM
191 Print NUM lines of leading context before matching lines.
192 Places a line containing a group separator (--) between
193 contiguous groups of matches. With the -o or --only-matching
194 option, this has no effect and a warning is given.
195 -C NUM, -NUM, --context=NUM
197 Print NUM lines of output context. Places a line containing a
198 group separator (--) between contiguous groups of matches. With
199 the -o or --only-matching option, this has no effect and a
200 warning is given.
201 --group-separator=SEP
203 When -A, -B, or -C are in use, print SEP instead of -- between
204 groups of lines.
205 --no-group-separator
207 When -A, -B, or -C are in use, do not print a separator between
208 groups of lines.
209 File and Directory Selection
211 -a, --text
212 Process a binary file as if it were text; this is equivalent to
213 the --binary-files=text option.
214 --binary-files=TYPE
216 If a file's data or metadata indicate that the file contains
217 binary data, assume that the file is of type TYPE. Non-text
218 bytes indicate binary data; these are either output bytes that
219 are improperly encoded for the current locale, or null input
220 bytes when the -z option is not given.
221 By default, TYPE is binary, and grep suppresses output after
223 null input binary data is discovered, and suppresses output
224 lines that contain improperly encoded data. When some output is
225 suppressed, grep follows any output with a message to standard
226 error saying that a binary file matches.
227 If TYPE is without-match, when grep discovers null input binary
229 data it assumes that the rest of the file does not match; this
230 is equivalent to the -I option.
231 If TYPE is text, grep processes a binary file as if it were
233 text; this is equivalent to the -a option.
234 When type is binary, grep may treat non-text bytes as line
236 terminators even without the -z option. This means choosing
237 binary versus text can affect whether a pattern matches a file.
238 For example, when type is binary the pattern q$ might match q
239 immediately followed by a null byte, even though this is not
240 matched when type is text. Conversely, when type is binary the
241 pattern . (period) might not match a null byte.
242 Warning: The -a option might output binary garbage, which can
244 have nasty side effects if the output is a terminal and if the
245 terminal driver interprets some of it as commands. On the other
246 hand, when reading files whose text encodings are unknown, it
247 can be helpful to use -a or to set LC_ALL='C' in the
248 environment, in order to find more matches even if the matches
249 are unsafe for direct display.
250 -D ACTION, --devices=ACTION
252 If an input file is a device, FIFO or socket, use ACTION to
253 process it. By default, ACTION is read, which means that
254 devices are read just as if they were ordinary files. If ACTION
255 is skip, devices are silently skipped.
256 -d ACTION, --directories=ACTION
258 If an input file is a directory, use ACTION to process it. By
259 default, ACTION is read, i.e., read directories just as if they
260 were ordinary files. If ACTION is skip, silently skip
261 directories. If ACTION is recurse, read all files under each
262 directory, recursively, following symbolic links only if they
263 are on the command line. This is equivalent to the -r option.
264 --exclude=GLOB
266 Skip any command-line file with a name suffix that matches the
267 pattern GLOB, using wildcard matching; a name suffix is either
268 the whole name, or a trailing part that starts with a non-slash
269 character immediately after a slash (/) in the name. When
270 searching recursively, skip any subfile whose base name matches
271 GLOB; the base name is the part after the last slash. A pattern
272 can use *, ?, and [...] as wildcards, and \ to quote a wildcard
273 or backslash character literally.
274 --exclude-from=FILE
276 Skip files whose base name matches any of the file-name globs
277 read from FILE (using wildcard matching as described under
278 --exclude).
279 --exclude-dir=GLOB
281 Skip any command-line directory with a name suffix that matches
282 the pattern GLOB. When searching recursively, skip any
283 subdirectory whose base name matches GLOB. Ignore any redundant
284 trailing slashes in GLOB.
285 -I Process a binary file as if it did not contain matching data;
287 this is equivalent to the --binary-files=without-match option.
288 --include=GLOB
290 Search only files whose base name matches GLOB (using wildcard
291 matching as described under --exclude). If contradictory
292 --include and --exclude options are given, the last matching one
293 wins. If no --include or --exclude options match, a file is
294 included unless the first such option is --include.
295 -r, --recursive
297 Read all files under each directory, recursively, following
298 symbolic links only if they are on the command line. Note that
299 if no file operand is given, grep searches the working
300 directory. This is equivalent to the -d recurse option.
301 -R, --dereference-recursive
303 Read all files under each directory, recursively. Follow all
304 symbolic links, unlike -r.
305 Other Options
307 --line-buffered
308 Use line buffering on output. This can cause a performance
309 penalty.
310 -U, --binary
312 Treat the file(s) as binary. By default, under MS-DOS and MS-
313 Windows, grep guesses whether a file is text or binary as
314 described for the --binary-files option. If grep decides the
315 file is a text file, it strips the CR characters from the
316 original file contents (to make regular expressions with ^ and $
317 work correctly). Specifying -U overrules this guesswork,
318 causing all files to be read and passed to the matching
319 mechanism verbatim; if the file is a text file with CR/LF pairs
320 at the end of each line, this will cause some regular
321 expressions to fail. This option has no effect on platforms
322 other than MS-DOS and MS-Windows.
323 -z, --null-data
325 Treat input and output data as sequences of lines, each
326 terminated by a zero byte (the ASCII NUL character) instead of a
327 newline. Like the -Z or --null option, this option can be used
328 with commands like sort -z to process arbitrary file names.
329
331 A regular expression is a pattern that describes a set of strings.
332 Regular expressions are constructed analogously to arithmetic
333 expressions, by using various operators to combine smaller expressions.
334 grep understands three different versions of regular expression syntax:
336 “basic” (BRE), “extended” (ERE) and “perl” (PCRE). In GNU grep there
337 is no difference in available functionality between basic and extended
338 syntax. In other implementations, basic regular expressions are less
339 powerful. The following description applies to extended regular
340 expressions; differences for basic regular expressions are summarized
341 afterwards. Perl-compatible regular expressions give additional
342 functionality, and are documented in pcre2syntax(3) and
343 pcre2pattern(3), but work only if PCRE support is enabled.
344 The fundamental building blocks are the regular expressions that match
346 a single character. Most characters, including all letters and digits,
347 are regular expressions that match themselves. Any meta-character with
348 special meaning may be quoted by preceding it with a backslash.
349 The period . matches any single character. It is unspecified whether
351 it matches an encoding error.
352 Character Classes and Bracket Expressions
354 A bracket expression is a list of characters enclosed by [ and ]. It
355 matches any single character in that list. If the first character of
356 the list is the caret ^ then it matches any character not in the list;
357 it is unspecified whether it matches an encoding error. For example,
358 the regular expression [0123456789] matches any single digit.
359 Within a bracket expression, a range expression consists of two
361 characters separated by a hyphen. It matches any single character that
362 sorts between the two characters, inclusive, using the locale's
363 collating sequence and character set. For example, in the default C
364 locale, [a-d] is equivalent to [abcd]. Many locales sort characters in
365 dictionary order, and in these locales [a-d] is typically not
366 equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.
367 To obtain the traditional interpretation of bracket expressions, you
368 can use the C locale by setting the LC_ALL environment variable to the
369 value C.
370 Finally, certain named classes of characters are predefined within
372 bracket expressions, as follows. Their names are self explanatory, and
373 they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:],
374 [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and
375 [:xdigit:]. For example, [[:alnum:]] means the character class of
376 numbers and letters in the current locale. In the C locale and ASCII
377 character set encoding, this is the same as [0-9A-Za-z]. (Note that
378 the brackets in these class names are part of the symbolic names, and
379 must be included in addition to the brackets delimiting the bracket
380 expression.) Most meta-characters lose their special meaning inside
381 bracket expressions. To include a literal ] place it first in the
382 list. Similarly, to include a literal ^ place it anywhere but first.
383 Finally, to include a literal - place it last.
384 Anchoring
386 The caret ^ and the dollar sign $ are meta-characters that respectively
387 match the empty string at the beginning and end of a line.
388 The Backslash Character and Special Expressions
390 The symbols \< and \> respectively match the empty string at the
391 beginning and end of a word. The symbol \b matches the empty string at
392 the edge of a word, and \B matches the empty string provided it's not
393 at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and
394 \W is a synonym for [^_[:alnum:]].
395 Repetition
397 A regular expression may be followed by one of several repetition
398 operators:
399 ? The preceding item is optional and matched at most once.
400 * The preceding item will be matched zero or more times.
401 + The preceding item will be matched one or more times.
402 {n} The preceding item is matched exactly n times.
403 {n,} The preceding item is matched n or more times.
404 {,m} The preceding item is matched at most m times. This is a GNU
405 extension.
406 {n,m} The preceding item is matched at least n times, but not more
407 than m times.
408 Concatenation
410 Two regular expressions may be concatenated; the resulting regular
411 expression matches any string formed by concatenating two substrings
412 that respectively match the concatenated expressions.
413 Alternation
415 Two regular expressions may be joined by the infix operator |; the
416 resulting regular expression matches any string matching either
417 alternate expression.
418 Precedence
420 Repetition takes precedence over concatenation, which in turn takes
421 precedence over alternation. A whole expression may be enclosed in
422 parentheses to override these precedence rules and form a
423 subexpression.
424 Back-references and Subexpressions
426 The back-reference \n, where n is a single digit, matches the substring
427 previously matched by the nth parenthesized subexpression of the
428 regular expression.
429 Basic vs Extended Regular Expressions
431 In basic regular expressions the meta-characters ?, +, {, |, (, and )
432 lose their special meaning; instead use the backslashed versions \?,
433 \+, \{, \|, \(, and \).
434
436 Normally the exit status is 0 if a line is selected, 1 if no lines were
437 selected, and 2 if an error occurred. However, if the -q or --quiet or
438 --silent is used and a line is selected, the exit status is 0 even if
439 an error occurred.
440
442 The behavior of grep is affected by the following environment
443 variables.
444 The locale for category LC_foo is specified by examining the three
446 environment variables LC_ALL, LC_foo, LANG, in that order. The first
447 of these variables that is set specifies the locale. For example, if
448 LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
449 Portuguese locale is used for the LC_MESSAGES category. The C locale
450 is used if none of these environment variables are set, if the locale
451 catalog is not installed, or if grep was not compiled with national
452 language support (NLS). The shell command locale -a lists locales that
453 are currently available.
454 GREP_COLORS
456 Specifies the colors and other attributes used to highlight
457 various parts of the output. Its value is a colon-separated
458 list of capabilities that defaults to
459 ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv
460 and ne boolean capabilities omitted (i.e., false). Supported
461 capabilities are as follows.
462 sl= SGR substring for whole selected lines (i.e., matching
464 lines when the -v command-line option is omitted, or non-
465 matching lines when -v is specified). If however the
466 boolean rv capability and the -v command-line option are
467 both specified, it applies to context matching lines
468 instead. The default is empty (i.e., the terminal's
469 default color pair).
470 cx= SGR substring for whole context lines (i.e., non-matching
472 lines when the -v command-line option is omitted, or
473 matching lines when -v is specified). If however the
474 boolean rv capability and the -v command-line option are
475 both specified, it applies to selected non-matching lines
476 instead. The default is empty (i.e., the terminal's
477 default color pair).
478 rv Boolean value that reverses (swaps) the meanings of the
480 sl= and cx= capabilities when the -v command-line option
481 is specified. The default is false (i.e., the capability
482 is omitted).
483 mt=01;31
485 SGR substring for matching non-empty text in any matching
486 line (i.e., a selected line when the -v command-line
487 option is omitted, or a context line when -v is
488 specified). Setting this is equivalent to setting both
489 ms= and mc= at once to the same value. The default is a
490 bold red text foreground over the current line
491 background.
492 ms=01;31
494 SGR substring for matching non-empty text in a selected
495 line. (This is only used when the -v command-line option
496 is omitted.) The effect of the sl= (or cx= if rv)
497 capability remains active when this kicks in. The
498 default is a bold red text foreground over the current
499 line background.
500 mc=01;31
502 SGR substring for matching non-empty text in a context
503 line. (This is only used when the -v command-line option
504 is specified.) The effect of the cx= (or sl= if rv)
505 capability remains active when this kicks in. The
506 default is a bold red text foreground over the current
507 line background.
508 fn=35 SGR substring for file names prefixing any content line.
510 The default is a magenta text foreground over the
511 terminal's default background.
512 ln=32 SGR substring for line numbers prefixing any content
514 line. The default is a green text foreground over the
515 terminal's default background.
516 bn=32 SGR substring for byte offsets prefixing any content
518 line. The default is a green text foreground over the
519 terminal's default background.
520 se=36 SGR substring for separators that are inserted between
522 selected line fields (:), between context line fields,
523 (-), and between groups of adjacent lines when nonzero
524 context is specified (--). The default is a cyan text
525 foreground over the terminal's default background.
526 ne Boolean value that prevents clearing to the end of line
528 using Erase in Line (EL) to Right (\33[K) each time a
529 colorized item ends. This is needed on terminals on
530 which EL is not supported. It is otherwise useful on
531 terminals for which the back_color_erase (bce) boolean
532 terminfo capability does not apply, when the chosen
533 highlight colors do not affect the background, or when EL
534 is too slow or causes too much flicker. The default is
535 false (i.e., the capability is omitted).
536 Note that boolean capabilities have no =... part. They are
538 omitted (i.e., false) by default and become true when specified.
539 See the Select Graphic Rendition (SGR) section in the
541 documentation of the text terminal that is used for permitted
542 values and their meaning as character attributes. These
543 substring values are integers in decimal representation and can
544 be concatenated with semicolons. grep takes care of assembling
545 the result into a complete SGR sequence (\33[...m). Common
546 values to concatenate include 1 for bold, 4 for underline, 5 for
547 blink, 7 for inverse, 39 for default foreground color, 30 to 37
548 for foreground colors, 90 to 97 for 16-color mode foreground
549 colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
550 foreground colors, 49 for default background color, 40 to 47 for
551 background colors, 100 to 107 for 16-color mode background
552 colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
553 background colors.
554 LC_ALL, LC_COLLATE, LANG
556 These variables specify the locale for the LC_COLLATE category,
557 which determines the collating sequence used to interpret range
558 expressions like [a-z].
559 LC_ALL, LC_CTYPE, LANG
561 These variables specify the locale for the LC_CTYPE category,
562 which determines the type of characters, e.g., which characters
563 are whitespace. This category also determines the character
564 encoding, that is, whether text is encoded in UTF-8, ASCII, or
565 some other encoding. In the C or POSIX locale, all characters
566 are encoded as a single byte and every byte is a valid
567 character.
568 LC_ALL, LC_MESSAGES, LANG
570 These variables specify the locale for the LC_MESSAGES category,
571 which determines the language that grep uses for messages. The
572 default C locale uses American English messages.
573 POSIXLY_CORRECT
575 If set, grep behaves as POSIX requires; otherwise, grep behaves
576 more like other GNU programs. POSIX requires that options that
577 follow file names must be treated as file names; by default,
578 such options are permuted to the front of the operand list and
579 are treated as options. Also, POSIX requires that unrecognized
580 options be diagnosed as “illegal”, but since they are not really
581 against the law the default is to diagnose them as “invalid”.
582 POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_,
583 described below.
584 _N_GNU_nonoption_argv_flags_
586 (Here N is grep's numeric process ID.) If the ith character of
587 this environment variable's value is 1, do not consider the ith
588 operand of grep to be an option, even if it appears to be one.
589 A shell can put this variable in the environment for each
590 command it runs, specifying which operands are the results of
591 file name wildcard expansion and therefore should not be treated
592 as options. This behavior is available only with the GNU C
593 library, and only when POSIXLY_CORRECT is not set.
594
596 This man page is maintained only fitfully; the full documentation is
597 often more up-to-date.
598
600 Copyright 1998-2000, 2002, 2005-2022 Free Software Foundation, Inc.
601 This is free software; see the source for copying conditions. There is
603 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
604 PURPOSE.
605
607 Reporting Bugs
608 Email bug reports to the bug-reporting address ⟨bug-grep@gnu.org⟩. An
609 email archive ⟨https://lists.gnu.org/mailman/listinfo/bug-grep⟩ and a
610 bug tracker ⟨https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep⟩
611 are available.
612 Known Bugs
614 Large repetition counts in the {n,m} construct may cause grep to use
615 lots of memory. In addition, certain other obscure regular expressions
616 require exponential time and space, and may cause grep to run out of
617 memory.
618 Back-references are very slow, and may require exponential time.
620
622 The following example outputs the location and contents of any line
623 containing “f” and ending in “.c”, within all files in the current di‐
624 rectory whose names contain “g” and end in “.h”. The -n option outputs
625 line numbers, the -- argument treats expansions of “*g*.h” starting
626 with “-” as file names not options, and the empty file /dev/null causes
627 file names to be output even if only one file name happens to be of the
628 form “*g*.h”.
629 $ grep -n -- 'f.*\.c$' *g*.h /dev/null
631 argmatch.h:1:/* definitions and prototypes for argmatch.c
632 The only line that matches is line 1 of argmatch.h. Note that the reg‐
634 ular expression syntax used in the pattern differs from the globbing
635 syntax that the shell uses to match file names.
636
638 Regular Manual Pages
639 awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1),
640 read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5),
641 glob(7), regex(7)
642 Full Documentation
644 A complete manual ⟨https://www.gnu.org/software/grep/manual/⟩ is avail‐
645 able. If the info and grep programs are properly installed at your
646 site, the command
647 info grep
649 should give you access to the complete manual.
651GNU grep 3.8 2019-12-29 GREP(1)