rgrep <root
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.

       -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  the  first  few  bytes  of  a file indicate that the file contains binary data,
              assume that the file is of type  TYPE.   By  default,  TYPE  is  binary,  and  grep
              normally 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, grep assumes that a binary
              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 processing binary data, grep may treat non-text bytes as line terminators; for
              example, the pattern '.' (period) might not match a null byte,  as  the  null  byte
              might  be  treated  as  a line terminator.  Warning: grep --binary-files=text 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.

       -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  files  whose  base  name matches GLOB (using wildcard matching).  A file-name
              glob 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=DIR
              Exclude directories matching the pattern DIR from recursive searches.

       -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
              the file type by looking at the contents of the first 32KB read from the file.   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 the input as a set 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).

       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.

       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 2.25                                   GREP(1)

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