GREP(1)                                                                               General Commands Manual                                                                              GREP(1)

NAME
       grep, egrep, fgrep, rgrep - print lines matching a pattern

SYNOPSIS
       grep [OPTIONS] PATTERN [FILE...]
       grep [OPTIONS] [-e PATTERN]...  [-f FILE]...  [FILE...]

DESCRIPTION
       grep  searches the named input FILEs for lines containing a match to the given PATTERN.  If no files are specified, or if the file “-” is given, grep searches standard input.  By default,
       grep prints the matching lines.

       In addition, the variant programs egrep, fgrep and rgrep are the same as grep -E, grep -F, and grep -r, respectively.  These  variants  are  deprecated,  but  are  provided  for  backward
       compatibility.

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

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

   Matcher Selection
       -E, --extended-regexp
              Interpret PATTERN as an extended regular expression (ERE, see below).

       -F, --fixed-strings
              Interpret PATTERN as a list of fixed strings (instead of regular expressions), separated by newlines, any of which is to be matched.

       -G, --basic-regexp
              Interpret PATTERN as a basic regular expression (BRE, see below).  This is the default.

       -P, --perl-regexp
              Interpret the pattern as a Perl-compatible regular expression (PCRE).  This is highly experimental and grep -P may warn of unimplemented features.

   Matching Control
       -e PATTERN, --regexp=PATTERN
              Use  PATTERN as the pattern.  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.

       -i, --ignore-case
              Ignore case distinctions in both the PATTERN and the input files.

       -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 $.

       -y     Obsolete synonym for -i.

   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 below), 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.   The  deprecated  environment  variable  GREP_COLOR  is  still
              supported, but its setting does not have priority.  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.  The scanning will stop on the first match.

       -l, --files-with-matches
              Suppress normal output; instead print the name of each input file from which output would normally have been printed.  The scanning will stop on the first match.

       -m NUM, --max-count=NUM
              Stop  reading  a  file  after  NUM  matching  lines.  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.

       -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 is especially useful when implementing tools like zgrep,  e.g.,  gzip  -cd  foo.gz  |  grep
              --label=foo -H something.  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.

       -u, --unix-byte-offsets
              Report  Unix-style  byte  offsets.   This  switch  causes  grep to report byte offsets as if the file were a Unix-style text file, i.e., with CR characters stripped off.  This will
              produce results identical to running grep on a Unix machine.  This option has no effect unless -b option is also used; it has no effect on  platforms  other  than  MS-DOS  and  MS-
              Windows.

       -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.

   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 when grep discovers that a file is binary it suppresses any further output, and instead outputs either a one-line message saying that a binary file
              matches, or no message if there is no match.

              If TYPE is without-match, when grep discovers that a file is binary 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 any suffix starting after a / and
              before a +non-/.  When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last /.  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).

       -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, there is no difference in available  functionality
       between  basic  and  extended  syntaxes.   In  other  implementations,  basic  regular  expressions  are less powerful.  The following description applies to extended regular expressions;
       differences for basic regular expressions are summarized afterwards.  Perl-compatible  regular  expressions  give  additional  functionality,  and  are  documented  in  pcresyntax(3)  and
       pcrepattern(3), but work only if PCRE is available in the system.

       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.

   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.  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:],  [: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 \?, \+, \{, \|, \(, and \).

ENVIRONMENT VARIABLES
       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_OPTIONS
              This variable specifies default options to be placed in front of any explicit options.  As this causes problems when writing portable scripts, this feature will  be  removed  in  a
              future release of grep, and grep warns if it is used.  Please use an alias or script instead.

       GREP_COLOR
              This  variable  specifies  the color used to highlight matched (non-empty) text.  It is deprecated in favor of GREP_COLORS, but still supported.  The mt, ms, and mc capabilities of
              GREP_COLORS have priority over it.  It can only specify the color used to highlight the matching non-empty text in any matching line (a  selected  line  when  the  -v  command-line
              option is omitted, or a context line when -v is specified).  The default is 01;31, which means a bold red foreground text on the terminal's default background.

       GREP_COLORS
              Specifies  the  colors  and  other  attributes  used  to  highlight  various  parts  of  the  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”.  POSIXLY_CORRECT also disables _N_GNU_nonoption_argv_flags_, described below.

       _N_GNU_nonoption_argv_flags_
              (Here  N is grep's numeric process ID.)  If the ith character of this environment variable's value is 1, do not consider the ith operand of grep to be an option, even if it appears
              to be one.  A shell can put this variable in the environment for each command it runs, specifying which operands are the results of  file  name  wildcard  expansion  and  therefore
              should not be treated as options.  This behavior is available only with the GNU C library, and only when POSIXLY_CORRECT is not set.

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.

COPYRIGHT
       Copyright 1998-2000, 2002, 2005-2016 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 ⟨bug-grep@gnu.org⟩.  An email archive ⟨http://lists.gnu.org/mailman/listinfo/bug-grep⟩ and a bug tracker ⟨http://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 expressions require exponential time and space, and may
       cause grep to run out of memory.

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

SEE ALSO
   Regular Manual Pages
       awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1), xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3), terminfo(5), glob(7), regex(7).

   POSIX Programmer's Manual Page
       grep(1p).

   Full Documentation
       A complete manual ⟨http://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.

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

User Commands                                                                              GNU grep 2.27                                                                                   GREP(1)