grep "pattern" file.txt

grep "pattern" file1.txt file2.txt

grep -r "pattern" directory/

grep -E "pattern|another" file.txt

grep "^pattern" file.txt

grep "pattern$" file.txt

grep -n "pattern" file.txt

grep -o "pattern" file.txt

grep -c "pattern" file.txt

grep -v "pattern" file.txt

grep -i "pattern" file.txt

grep -e "pattern1" -e "pattern2" file.txt

grep -C 3 "pattern" file.txt

grep -B 3 "pattern" file.txt

grep -A 3 "pattern" file.txt

grep -a "pattern" binaryfile

grep --binary-files=without-match "pattern" *

GREP(1)                                                            User Commands                                                           GREP(1)

NAME
       grep, egrep, fgrep, rgrep - print lines that match patterns

SYNOPSIS
       grep [OPTION...] PATTERNS [FILE...]
       grep [OPTION...] -e PATTERNS ... [FILE...]
       grep [OPTION...] -f PATTERN_FILE ... [FILE...]

DESCRIPTION
       grep  searches for PATTERNS in each FILE.  PATTERNS is one or more patterns separated by newline characters, and grep prints each line that
       matches a pattern.  Typically PATTERNS should be quoted when grep is used in a shell command.

       A FILE of “-” stands for standard input.  If no FILE is given, recursive searches examine the working directory, and nonrecursive  searches
       read standard input.

       Debian  also  includes  the  variant  programs  egrep,  fgrep  and  rgrep.   These  programs are the same as grep -E, grep -F, and grep -r,
       respectively.  These variants are deprecated upstream, but Debian provides for backward  compatibility.  For  portability  reasons,  it  is
       recommended to avoid the variant programs, and use grep with the related option instead.

OPTIONS
   Generic Program Information
       --help Output a usage message and exit.

       -V, --version
              Output the version number of grep and exit.

   Pattern Syntax
       -E, --extended-regexp
              Interpret PATTERNS as extended regular expressions (EREs, see below).

       -F, --fixed-strings
              Interpret PATTERNS as fixed strings, not regular expressions.

       -G, --basic-regexp
              Interpret PATTERNS as basic regular expressions (BREs, see below).  This is the default.

       -P, --perl-regexp
              Interpret  PATTERNS  as  Perl-compatible  regular  expressions  (PCREs).   This  option  is  experimental  when combined with the -z
              (--null-data) option, and grep -P may warn of unimplemented features.

   Matching Control
       -e PATTERNS, --regexp=PATTERNS
              Use PATTERNS as the patterns.  If this option is used multiple times or is combined with the -f  (--file)  option,  search  for  all
              patterns given.  This option can be used to protect a pattern beginning with “-”.

       -f FILE, --file=FILE
              Obtain patterns from FILE, one per line.  If this option is used multiple times or is combined with the -e (--regexp) option, search
              for  all  patterns  given.  The empty file contains zero patterns, and therefore matches nothing.  If FILE is - , read patterns from
              standard input.

       -i, --ignore-case
              Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other.

       --no-ignore-case
              Do not ignore case distinctions in patterns and input data.  This is the default.  This  option  is  useful  for  passing  to  shell
              scripts that already use -i, to cancel its effects because the two options override each other.

       -v, --invert-match
              Invert the sense of matching, to select non-matching lines.

       -w, --word-regexp
              Select  only  those  lines  containing matches that form whole words.  The test is that the matching substring must either be at the
              beginning of the line, or preceded by a non-word constituent character.  Similarly, it must be either at the  end  of  the  line  or
              followed by a non-word constituent character.  Word-constituent characters are letters, digits, and the underscore.  This option has
              no effect if -x is also specified.

       -x, --line-regexp
              Select  only  those  matches  that  exactly match the whole line.  For a regular expression pattern, this is like parenthesizing the
              pattern and then surrounding it with ^ and $.

   General Output Control
       -c, --count
              Suppress normal output; instead print a count of matching lines for each input  file.   With  the  -v,  --invert-match  option  (see
              above), count non-matching lines.

       --color[=WHEN], --colour[=WHEN]
              Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for
              fields  and  groups of context lines) with escape sequences to display them in color on the terminal.  The colors are defined by the
              environment variable GREP_COLORS.  WHEN is never, always, or auto.

       -L, --files-without-match
              Suppress normal output; instead print the name of each input file from which no output would normally have been printed.

       -l, --files-with-matches
              Suppress normal output; instead print the name of each input file from which output would normally have been printed.  Scanning each
              input file stops upon first match.

       -m NUM, --max-count=NUM
              Stop reading a file after NUM matching lines.  If NUM is zero, grep stops right away without reading input.  A NUM of -1 is  treated
              as infinity and grep does not stop; this is the default.  If the input is standard input from a regular file, and NUM matching lines
              are  output,  grep  ensures that the standard input is positioned to just after the last matching line before exiting, regardless of
              the presence of trailing context lines.  This enables a calling process to resume a search.  When  grep  stops  after  NUM  matching
              lines, it outputs any trailing context lines.  When the -c or --count option is also used, grep does not output a count greater than
              NUM.  When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines.

       -o, --only-matching
              Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.

       -q, --quiet, --silent
              Quiet;  do  not  write  anything  to standard output.  Exit immediately with zero status if any match is found, even if an error was
              detected.  Also see the -s or --no-messages option.

       -s, --no-messages
              Suppress error messages about nonexistent or unreadable files.

   Output Line Prefix Control
       -b, --byte-offset
              Print the 0-based byte offset within the input file before each line of output.  If -o (--only-matching)  is  specified,  print  the
              offset of the matching part itself.

       -H, --with-filename
              Print the file name for each match.  This is the default when there is more than one file to search.  This is a GNU extension.

       -h, --no-filename
              Suppress the prefixing of file names on output.  This is the default when there is only one file (or only standard input) to search.

       --label=LABEL
              Display input actually coming from standard input as input coming from file LABEL.  This can be useful for commands that transform a
              file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'.  See also the -H option.

       -n, --line-number
              Prefix each line of output with the 1-based line number within its input file.

       -T, --initial-tab
              Make  sure  that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal.  This is
              useful with options that prefix their output to the actual content: -H,-n, and -b.  In order to improve the probability  that  lines
              from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in
              a minimum size field width.

       -Z, --null
              Output  a  zero  byte  (the  ASCII NUL character) instead of the character that normally follows a file name.  For example, grep -lZ
              outputs a zero byte after each file name instead of the usual newline.  This option  makes  the  output  unambiguous,  even  in  the
              presence  of  file names containing unusual characters like newlines.  This option can be used with commands like find -print0, perl
              -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters.

   Context Line Control
       -A NUM, --after-context=NUM
              Print NUM lines of trailing context after matching lines.  Places a line containing a group separator (--) between contiguous groups
              of matches.  With the -o or --only-matching option, this has no effect and a warning is given.

       -B NUM, --before-context=NUM
              Print NUM lines of leading context before matching lines.  Places a line containing a group separator (--) between contiguous groups
              of matches.  With the -o or --only-matching option, this has no effect and a warning is given.

       -C NUM, -NUM, --context=NUM
              Print NUM lines of output context.  Places a line containing a group separator (--) between contiguous groups of matches.  With  the
              -o or --only-matching option, this has no effect and a warning is given.

       --group-separator=SEP
              When -A, -B, or -C are in use, print SEP instead of -- between groups of lines.

       --no-group-separator
              When -A, -B, or -C are in use, do not print a separator between groups of lines.

   File and Directory Selection
       -a, --text
              Process a binary file as if it were text; this is equivalent to the --binary-files=text option.

       --binary-files=TYPE
              If  a  file's  data  or  metadata indicate that the file contains binary data, assume that the file is of type TYPE.  Non-text bytes
              indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the
              -z option is not given.

              By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines  that
              contain  improperly  encoded  data.  When some output is suppressed, grep follows any output with a message to standard error saying
              that a binary file matches.

              If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not  match;  this  is
              equivalent to the -I option.

              If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option.

              When  type  is  binary,  grep  may  treat non-text bytes as line terminators even without the -z option.  This means choosing binary
              versus text can affect whether a pattern matches a file.  For example, when type is binary the pattern q$ might match q  immediately
              followed  by a null byte, even though this is not matched when type is text.  Conversely, when type is binary the pattern . (period)
              might not match a null byte.

              Warning: The -a option might output binary garbage, which can have nasty side effects if  the  output  is  a  terminal  and  if  the
              terminal  driver  interprets some of it as commands.  On the other hand, when reading files whose text encodings are unknown, it can
              be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even  if  the  matches  are  unsafe  for
              direct display.

       -D ACTION, --devices=ACTION
              If  an  input  file is a device, FIFO or socket, use ACTION to process it.  By default, ACTION is read, which means that devices are
              read just as if they were ordinary files.  If ACTION is skip, devices are silently skipped.

       -d ACTION, --directories=ACTION
              If an input file is a directory, use ACTION to process it.  By default, ACTION is read, i.e., read directories just as if they  were
              ordinary  files.   If  ACTION  is  skip,  silently  skip  directories.   If  ACTION is recurse, read all files under each directory,
              recursively, following symbolic links only if they are on the command line.  This is equivalent to the -r option.

       --exclude=GLOB
              Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix  is  either  the
              whole  name,  or  a  trailing part that starts with a non-slash character immediately after a slash (/) in the name.  When searching
              recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash.  A pattern can use *, ?,
              and [...] as wildcards, and \ to quote a wildcard or backslash character literally.

       --exclude-from=FILE
              Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude).

       --exclude-dir=GLOB
              Skip any command-line directory with a name suffix that matches the pattern GLOB.  When searching recursively, skip any subdirectory
              whose base name matches GLOB.  Ignore any redundant trailing slashes in GLOB.

       -I     Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option.

       --include=GLOB
              Search only files whose base name matches GLOB (using wildcard matching as described under --exclude).  If  contradictory  --include
              and  --exclude options are given, the last matching one wins.  If no --include or --exclude options match, a file is included unless
              the first such option is --include.

       -r, --recursive
              Read all files under each directory, recursively, following symbolic links only if they are on the command line.  Note  that  if  no
              file operand is given, grep searches the working directory.  This is equivalent to the -d recurse option.

       -R, --dereference-recursive
              Read all files under each directory, recursively.  Follow all symbolic links, unlike -r.

   Other Options
       --line-buffered
              Use line buffering on output.  This can cause a performance penalty.

       -U, --binary
              Treat  the  file(s)  as binary.  By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described
              for the --binary-files option.  If grep decides the file is a text file, it strips the CR characters from the original file contents
              (to make regular expressions with ^ and $ work correctly).  Specifying -U overrules this guesswork, causing all files to be read and
              passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some
              regular expressions to fail.  This option has no effect on platforms other than MS-DOS and MS-Windows.

       -z, --null-data
              Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead  of  a  newline.
              Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names.

REGULAR EXPRESSIONS
       A  regular  expression  is  a  pattern  that  describes  a  set  of strings.  Regular expressions are constructed analogously to arithmetic
       expressions, by using various operators to combine smaller expressions.

       grep understands three different versions of regular expression syntax: “basic” (BRE), “extended” (ERE) and “perl” (PCRE).   In  GNU  grep,
       basic  and  extended  regular  expressions  are  merely  different  notations  for  the  same  pattern-matching  functionality.   In  other
       implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around.  The
       following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards.   Perl-
       compatible  regular  expressions  have  different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if
       PCRE support is enabled.

       The fundamental building blocks are the regular expressions that match a single character.  Most  characters,  including  all  letters  and
       digits,  are  regular  expressions  that  match  themselves.   Any meta-character with special meaning may be quoted by preceding it with a
       backslash.

       The period . matches any single character.  It is unspecified whether it matches an encoding error.

   Character Classes and Bracket Expressions
       A bracket expression is a list of characters enclosed by [ and ].  It matches any single character in that list.  If the first character of
       the list is the caret ^ then it matches any character not in the list; it is  unspecified  whether  it  matches  an  encoding  error.   For
       example, the regular expression [0123456789] matches any single digit.

       Within  a  bracket  expression,  a range expression consists of two characters separated by a hyphen.  It matches any single character that
       sorts between the two characters, inclusive, using the locale's collating sequence and character  set.   For  example,  in  the  default  C
       locale,  [a-d]  is  equivalent  to  [abcd].   Many locales sort characters in dictionary order, and in these locales [a-d] is typically not
       equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example.  To obtain the traditional interpretation of  bracket  expressions,
       you can use the C locale by setting the LC_ALL environment variable to the value C.

       Finally,  certain named classes of characters are predefined within bracket expressions, as follows.  Their names are self explanatory, and
       they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:],  [:lower:],  [:print:],  [:punct:],  [:space:],  [:upper:],  and
       [:xdigit:].   For  example,  [[:alnum:]] means the character class of numbers and letters in the current locale.  In the C locale and ASCII
       character set encoding, this is the same as [0-9A-Za-z].  (Note that the brackets in these class names are part of the symbolic names,  and
       must  be  included  in addition to the brackets delimiting the bracket expression.)  Most meta-characters lose their special meaning inside
       bracket expressions.  To include a literal ] place it first in the list.  Similarly, to include a literal ^ place it  anywhere  but  first.
       Finally, to include a literal - place it last.

   Anchoring
       The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line.

   The Backslash Character and Special Expressions
       The  symbols  \<  and \> respectively match the empty string at the beginning and end of a word.  The symbol \b matches the empty string at
       the edge of a word, and \B matches the empty string provided it's not at the edge of a word.  The symbol \w is a synonym  for  [_[:alnum:]]
       and \W is a synonym for [^_[:alnum:]].

   Repetition
       A regular expression may be followed by one of several repetition operators:
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {,m}   The preceding item is matched at most m times.  This is a GNU extension.
       {n,m}  The preceding item is matched at least n times, but not more than m times.

   Concatenation
       Two  regular  expressions  may  be concatenated; the resulting regular expression matches any string formed by concatenating two substrings
       that respectively match the concatenated expressions.

   Alternation
       Two regular expressions may be joined by the infix operator |;  the  resulting  regular  expression  matches  any  string  matching  either
       alternate expression.

   Precedence
       Repetition  takes  precedence  over  concatenation, which in turn takes precedence over alternation.  A whole expression may be enclosed in
       parentheses to override these precedence rules and form a subexpression.

   Back-references and Subexpressions
       The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized  subexpression  of  the
       regular expression.

   Basic vs Extended Regular Expressions
       In  basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?,
       \+, \{, \|, \(, and \).

EXIT STATUS
       Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an  error  occurred.   However,  if  the  -q  or
       --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred.

ENVIRONMENT
       The behavior of grep is affected by the following environment variables.

       The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order.  The first of
       these  variables  that is set specifies the locale.  For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian
       Portuguese locale is used for the LC_MESSAGES category.  The C locale is used if none of these environment variables are set, if the locale
       catalog is not installed, or if grep was not compiled with national language support (NLS).  The shell command locale -a lists locales that
       are currently available.

       GREP_COLORS
              Controls how the --color option highlights  output.   Its  value  is  a  colon-separated  list  of  capabilities  that  defaults  to
              ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36  with  the  rv  and  ne  boolean  capabilities  omitted  (i.e., false).  Supported
              capabilities are as follows.

              sl=    SGR substring for whole selected lines (i.e., matching lines when the -v command-line  option  is  omitted,  or  non-matching
                     lines  when  -v  is  specified).   If however the boolean rv capability and the -v command-line option are both specified, it
                     applies to context matching lines instead.  The default is empty (i.e., the terminal's default color pair).

              cx=    SGR substring for whole context lines (i.e., non-matching lines when the -v command-line option is omitted, or matching lines
                     when -v is specified).  If however the boolean rv capability and the -v command-line option are both specified, it applies to
                     selected non-matching lines instead.  The default is empty (i.e., the terminal's default color pair).

              rv     Boolean value that reverses (swaps) the meanings of the  sl=  and  cx=  capabilities  when  the  -v  command-line  option  is
                     specified.  The default is false (i.e., the capability is omitted).

              mt=01;31
                     SGR  substring  for  matching  non-empty  text in any matching line (i.e., a selected line when the -v command-line option is
                     omitted, or a context line when -v is specified).  Setting this is equivalent to setting both ms= and mc= at once to the same
                     value.  The default is a bold red text foreground over the current line background.

              ms=01;31
                     SGR substring for matching non-empty text in a selected line.  (This  is  only  used  when  the  -v  command-line  option  is
                     omitted.)  The effect of the sl= (or cx= if rv) capability remains active when this kicks in.  The default is a bold red text
                     foreground over the current line background.

              mc=01;31
                     SGR  substring  for  matching  non-empty  text  in  a  context  line.   (This is only used when the -v command-line option is
                     specified.)  The effect of the cx= (or sl= if rv) capability remains active when this kicks in.  The default is  a  bold  red
                     text foreground over the current line background.

              fn=35  SGR  substring  for  file  names  prefixing  any  content line.  The default is a magenta text foreground over the terminal's
                     default background.

              ln=32  SGR substring for line numbers prefixing any content line.  The default is  a  green  text  foreground  over  the  terminal's
                     default background.

              bn=32  SGR  substring  for  byte  offsets  prefixing  any  content line.  The default is a green text foreground over the terminal's
                     default background.

              se=36  SGR substring for separators that are inserted between selected line fields  (:),  between  context  line  fields,  (-),  and
                     between  groups  of  adjacent  lines  when nonzero context is specified (--).  The default is a cyan text foreground over the
                     terminal's default background.

              ne     Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized  item
                     ends.   This  is  needed  on  terminals  on  which  EL  is  not supported.  It is otherwise useful on terminals for which the
                     back_color_erase (bce) boolean terminfo capability does not apply, when  the  chosen  highlight  colors  do  not  affect  the
                     background, or when EL is too slow or causes too much flicker.  The default is false (i.e., the capability is omitted).

              Note that boolean capabilities have no =... part.  They are omitted (i.e., false) by default and become true when specified.

              See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their
              meaning  as  character  attributes.   These  substring  values  are  integers in decimal representation and can be concatenated with
              semicolons.  grep takes care of assembling the result into a complete SGR sequence (\33[...m).  Common values to concatenate include
              1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90  to  97
              for  16-color  mode  foreground  colors,  38;5;0  to  38;5;255  for  88-color  and 256-color modes foreground colors, 49 for default
              background color, 40 to 47 for background colors, 100 to 107 for 16-color  mode  background  colors,  and  48;5;0  to  48;5;255  for
              88-color and 256-color modes background colors.

       LC_ALL, LC_COLLATE, LANG
              These  variables  specify  the  locale  for the LC_COLLATE category, which determines the collating sequence used to interpret range
              expressions like [a-z].

       LC_ALL, LC_CTYPE, LANG
              These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g.,  which  characters  are
              whitespace.   This  category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other
              encoding.  In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character.

       LC_ALL, LC_MESSAGES, LANG
              These variables specify the locale for the LC_MESSAGES category, which determines the language that grep  uses  for  messages.   The
              default C locale uses American English messages.

       POSIXLY_CORRECT
              If  set,  grep  behaves  as  POSIX requires; otherwise, grep behaves more like other GNU programs.  POSIX requires that options that
              follow file names must be treated as file names; by default, such options are permuted to the front of  the  operand  list  and  are
              treated as options.  Also, POSIX requires that unrecognized options be diagnosed as “illegal”, but since they are not really against
              the law the default is to diagnose them as “invalid”.

NOTES
       This man page is maintained only fitfully; the full documentation is often more up-to-date.

COPYRIGHT
       Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc.

       This  is  free  software;  see  the  source  for  copying  conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
       PARTICULAR PURPOSE.

BUGS
   Reporting Bugs
       Email bug reports to the bug-reporting address ⟨[email protected]⟩.  An email archive ⟨https://lists.gnu.org/mailman/listinfo/bug-grep⟩  and
       a bug tracker ⟨https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep⟩ are available.

   Known Bugs
       Large  repetition  counts  in the {n,m} construct may cause grep to use lots of memory.  In addition, certain other obscure regular expres‐
       sions require exponential time and space, and may cause grep to run out of memory.

       Back-references are very slow, and may require exponential time.

EXAMPLE
       The following example outputs the location and contents of any line containing “f” and ending in “.c”, within all files in the current  di‐
       rectory whose names contain “g” and end in “.h”.  The -n option outputs line numbers, the -- argument treats expansions of “*g*.h” starting
       with “-” as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of
       the form “*g*.h”.

         $ grep -n -- 'f.*\.c$' *g*.h /dev/null
         argmatch.h:1:/* definitions and prototypes for argmatch.c

       The  only line that matches is line 1 of argmatch.h.  Note that the regular expression syntax used in the pattern differs from the globbing
       syntax that the shell uses to match file names.

SEE ALSO
   Regular Manual Pages
       awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1),  read(2),  pcre2(3),  pcre2syntax(3),  pcre2pattern(3),  terminfo(5),
       glob(7), regex(7)

   Full Documentation
       A  complete  manual ⟨https://www.gnu.org/software/grep/manual/⟩ is available.  If the info and grep programs are properly installed at your
       site, the command

              info grep

       should give you access to the complete manual.

GNU grep 3.11                                                       2019-12-29                                                             GREP(1)