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       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]


       Grep  searches the named input FILEs (or standard input if
       no files are named, or the file name - is given) for lines
       containing a match to the given PATTERN.  By default, grep
       prints the matching lines.

       In addition, two variant  programs  egrep  and  fgrep  are
       available.   Egrep  is  the same as grep -E.  Fgrep is the
       same as grep -F.


       -A NUM, --after-context=NUM
              Print NUM lines of trailing context after  matching
              lines.   Places  a  line containing -- between con­
              tiguous groups of matches.

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

       -B NUM, --before-context=NUM
              Print  NUM lines of leading context before matching
              lines.  Places a line containing  --  between  con­
              tiguous groups of matches.

       -C NUM, --context=NUM
              Print  NUM  lines of output context.  Places a line
              containing -- between contiguous groups of matches.

       -b, --byte-offset
              Print  the byte offset within the input file before
              each line of output.

              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.   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.
              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 pro­
              cess  it.   By default, ACTION is read, which means
              that directories are read  just  as  if  they  were
              ordinary files.  If ACTION is skip, directories are
              silently skipped.  If ACTION is recurse, grep reads
              all  files  under each directory, recursively; this
              is equivalent to the -r option.

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

       -e PATTERN, --regexp=PATTERN
              Use  PATTERN as the pattern; useful to protect pat­
              terns beginning with -.

       -F, --fixed-strings
              Interpret PATTERN as a list of fixed strings, sepa­
              rated  by  newlines, any of which is to be matched.
              -P, --perl-regexp Interpret PATTERN as a Perl regu­
              lar expression.

       -f FILE, --file=FILE
              Obtain patterns from FILE, one per line.  The empty
              file contains zero patterns, and therefore  matches

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

       -H, --with-filename
              Print the filename for each match.

       -h, --no-filename
              Suppress the prefixing of filenames on output  when
              multiple files are searched.

       --help Output a brief help message.

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

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

       -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.

       --mmap If possible, use the mmap(2) system  call  to  read
              input,  instead of the default read(2) system call.
              In some situations, --mmap  yields  better  perfor­
              mance.   However, --mmap can cause undefined behav­
              ior (including core dumps) if an input file shrinks
              while grep is operating, or if an I/O error occurs.

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

       -o, --only-matching
              Show  only the part of a matching line that matches

              Displays input actually coming from standard  input
              as  input  coming  from  file LABEL.  This is espe­
              cially useful for tools like zgrep, e.g.  gzip  -cd
              foo.gz |grep --label=foo something

              Use  line buffering, it can be a performance penal­

       -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.

       -R, -r, --recursive
              Read  all  files under each directory, recursively;
              this is equivalent to the -d recurse option.

              Recurse in directories only searching file matching

       -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.

       -u, --unix-byte-offsets
              Report Unix-style byte offsets.  This switch causes
              grep to report byte offsets as  if  the  file  were
              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-Win­

       -V, --version
              Print the version number of grep to standard error.
              This  version  number should be included in all bug
              reports (see below).

       -v, --invert-match
              Invert the sense of matching, to select  non-match­
              ing 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 charac­
              ter.   Similarly,  it  must be either at the end of
              the line or  followed  by  a  non-word  constituent
              character.   Word-constituent  characters  are let­
              ters, digits, and the underscore.

       -x, --line-regexp
              Select only those matches that  exactly  match  the
              whole line.

       -y     Obsolete synonym for -i.

       -Z, --null
       to  arithmetic  expressions, by using various operators to
       combine smaller expressions.

       Grep understands two different versions of regular expres­
       sion  syntax:  "basic" and "extended."  In GNU grep, there
       is no difference in available functionality  using  either
       syntax.   In  other implementations, basic regular expres­
       sions  are  less  powerful.   The  following   description
       applies  to  extended regular expressions; differences for
       basic regular expressions are summarized afterwards.

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

       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 char­
       acter 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 [aBbC­
       cDd],  for example.  To obtain the traditional interpreta­
       tion 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 prede­
       fined 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 [0-9A-Za-z], except the  latter
       form  depends  upon  the  C locale and the ASCII character
       encoding, whereas the former is independent of locale  and
       character  set.   (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 list.)
       Most metacharacters  lose  their  special  meaning  inside
       lists.  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.

       The period .  matches any single character.  The symbol \w
       *      The  preceding  item  will  be matched zero or more
       +      The preceding item will  be  matched  one  or  more
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {n,m}  The preceding item is matched at least n times, but
              not more than m times.

       Two regular expressions may be concatenated; the resulting
       regular  expression  matches any string formed by concate­
       nating two substrings that respectively match the concate­
       nated subexpressions.

       Two  regular expressions may be joined by the infix opera­
       tor |; the resulting regular expression matches any string
       matching either subexpression.

       Repetition  takes  precedence over concatenation, which in
       turn takes precedence over alternation.   A  whole  subex­
       pression  may be enclosed in parentheses to override these
       precedence rules.

       The backreference \n, where n is a single  digit,  matches
       the  substring previously matched by the nth parenthesized
       subexpression of the regular expression.

       In basic regular expressions the metacharacters ?,  +,  {,
       |,  (,  and  ) lose their special meaning; instead use the
       backslashed versions \?, \+, \{, \|, \(, and \).

       Traditional egrep did not support the { metacharacter, and
       some egrep implementations support \{ instead, so portable
       scripts should avoid { in egrep patterns  and  should  use
       [{] to match a literal {.

       GNU  egrep attempts to support traditional usage by assum­
       ing that { is not special if it would be the start  of  an
       invalid  interval  specification.   For example, the shell
       command egrep '{1' searches for the  two-character  string
       {1  instead  of  reporting  a  syntax error in the regular
       expression.  POSIX.2 allows this behavior as an extension,
       but portable scripts should avoid it.


       Grep's  behavior  is affected by the following environment

       A locale LC_foo is specified by examining the three  envi­
       ronment  variables  LC_ALL,  LC_foo,  LANG, in that order.
       The first of these variables that  is  set  specifies  the
              explicit options.  Option specifications are  sepa­
              rated  by whitespace.  A backslash escapes the next
              character, so it can be used to specify  an  option
              containing whitespace or a backslash.

              Specifies the marker for highlighting.

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

              These  variables specify the LC_CTYPE locale, which
              determines the  type  of  characters,  e.g.,  which
              characters are whitespace.

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

              If set, grep behaves as  POSIX.2  requires;  other­
              wise,  grep  behaves  more like other GNU programs.
              POSIX.2 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.2 requires that unrecognized options be diag­
              nosed  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.

              (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  com­
              mand  it  runs,  specifying  which operands are the
              results of file name wildcard expansion and  there­
              fore should not be treated as options.  This behav­
              ior is available only with the GNU C  library,  and
              only when POSIXLY_CORRECT is not set.


       Normally, exit status is 0 if selected lines are found and
       1 otherwise.  But  the  exit  status  is  2  if  an  error

GNU Project                 2002/01/22                    GREP(1)

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