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grep(1)                          User Commands                         grep(1)




NAME

       grep, egrep, fgrep - print lines that match patterns


SYNOPSIS

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


DESCRIPTION

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

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

       In addition, the variant programs egrep  and  fgrep  are  the  same  as
       grep -E  and grep -F, 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.

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

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

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

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

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

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

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

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

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

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

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

       -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 can be useful for commands that
              transform a file's contents before  searching,  e.g.,  gzip  -cd
              foo.gz  |  grep  --label=foo -H 'some pattern'.  See also the -H
              option.

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

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

       -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 grep suppresses output after
              null input binary data  is  discovered,  and  suppresses  output
              lines that contain improperly encoded data.  When some output is
              suppressed, grep follows any  output  with  a  one-line  message
              saying that a binary file matches.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


REGULAR EXPRESSIONS

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

       grep understands three different versions of regular expression syntax:
       "basic"  (BRE),  "extended" (ERE) and "perl" (PCRE).  In GNU grep 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.  It is unspecified whether
       it matches an encoding error.

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

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

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

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

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

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

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

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

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

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

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


EXIT STATUS

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


ENVIRONMENT

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

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

       GREP_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.


NOTES

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


COPYRIGHT

       Copyright 1998-2000, 2002, 2005-2020 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 <https://lists.gnu.org/mailman/listinfo/bug-grep>  and  a
       bug   tracker  <https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep>
       are available.

   Known Bugs
       Large repetition counts in the {n,m} construct may cause  grep  to  use
       lots of memory.  In addition, certain other obscure regular 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.


EXAMPLE

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

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

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


SEE ALSO

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

   Full Documentation
       A complete manual <https://www.gnu.org/software/grep/manual/> is avail-
       able.   If  the  info  and grep programs are properly installed at your
       site, the command

              info grep

       should give you access to the complete manual.



GNU grep 3.6                      2019-12-29                           grep(1)

grep 3.6 - Generated Tue Nov 10 08:16:08 CST 2020
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