egrep


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

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

       In  addition,  three  variant  programs  egrep,  fgrep  and  rgrep  are
       available.   egrep  is  the  same  as  grep -E.   fgrep  is the same as
       grep -F.  rgrep is the same as grep -r.  Direct  invocation  as  either
       egrep  or  fgrep  is  deprecated,  but  is provided to allow historical
       applications that rely on them to run unmodified.

OPTIONS
   Generic Program Information
       --help Print a usage message  briefly  summarizing  these  command-line
              options and the bug-reporting address, then exit.

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

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

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

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

       -P, --perl-regexp
              Interpret  PATTERN as a Perl regular expression.  This is highly
              experimental and grep -P may warn of unimplemented features.

   Matching Control
       -e PATTERN, --regexp=PATTERN
              Use PATTERN as  the  pattern.   This  can  be  used  to  specify
              multiple search patterns, or to protect a pattern beginning with
              a hyphen (-).  (-e is specified by POSIX.)

       -f FILE, --file=FILE
              Obtain patterns  from  FILE,  one  per  line.   The  empty  file
              contains  zero  patterns, and therefore matches nothing.  (-f is
              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.
              (-x is specified by POSIX.)

       -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.  (-c is specified by POSIX.)

       --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.   (-l  is  specified  by
              POSIX.)

       -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,
              like  GNU  grep's  -q option.  USG-style grep also lacked -q but
              its -s option behaved like GNU  grep.   Portable  shell  scripts
              should  avoid  both  -q  and -s and should redirect standard and
              error output to /dev/null instead.  (-s is specified by POSIX.)

   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  for  tools
              like zgrep, e.g., gzip -cd foo.gz | grep --label=foo something

       -n, --line-number
              Prefix  each  line of output with the 1-based line number within
              its input file.  (-n is specified by POSIX.)

       -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
              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.  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, 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.

       --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

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

       --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 performance.  However, --mmap can cause  undefined
              behavior  (including  core dumps) if an input file shrinks while
              grep is operating, or if an I/O error occurs.

       -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  two different versions of regular expression syntax:
       "basic" and  "extended."   In  GNU grep,  there  is  no  difference  in
       available functionality using either syntax.  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.

       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.
       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  [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
       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.
       {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.
       implementations  support \{ instead, so portable scripts should avoid {
       in grep -E patterns and should use [{] to match a literal {.

       GNU grep -E attempts to support traditional usage by assuming that { is
       not   special  if  it  would  be  the  start  of  an  invalid  interval
       specification.  For example, the command grep -E '{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.

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.   For  example,   if   GREP_OPTIONS   is
              '--binary-files=without-match  --directories=skip', grep behaves
              as  if  the   two   options   --binary-files=without-match   and
              --directories=skip   had  been  specified  before  any  explicit
              options.  Option specifications are separated by whitespace.   A
              backslash  escapes  the  next  character,  so  it can be used to
              specify an option containing whitespace or a backslash.

       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-
                     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

              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.2  requires;  otherwise,  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 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  selected lines are found and 1
       otherwise.  But the exit status is 2 if an error occurred,  unless  the
       -q  or --quiet or --silent option is used and a selected line is found.
       Note, however, that POSIX only mandates, for  programs  such  as  grep,
       cmp, and diff, that the exit status in case of error be greater than 1;

BUGS
   Reporting Bugs
       Email  bug reports to <bug-grep@gnu.org>, a mailing list whose web page
       is <http://lists.gnu.org/mailman/listinfo/bug-grep>.   grep's  Savannah
       bug tracker is located at <http://savannah.gnu.org/bugs/?group=grep>.

   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),   mmap(2),   read(2),   pcre(3),  pcrepattern(3),
       terminfo(5), glob(7), regex(7).

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

   TeXinfo Documentation
       The full documentation for grep is maintained as a TeXinfo manual.   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
       GNU's not Unix, but Unix is a beast; its plural form is Unixen.



GNU grep 2.5.1-cvs                2008-02-07                           GREP(1)
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