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GREP(1P)		   POSIX Programmer's Manual		      GREP(1P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       grep - search a file for a pattern

SYNOPSIS
       grep [-E| -F][-c| -l| -q][-insvx] -e pattern_list...
	       [-f pattern_file]...[file...]

       grep [-E| -F][-c| -l| -q][-insvx][-e pattern_list]...
	       -f pattern_file...[file...]

       grep [-E| -F][-c| -l| -q][-insvx] pattern_list[file...]

DESCRIPTION
       The grep utility shall search the input files, selecting lines matching
       one  or	more  patterns;	 the  types  of patterns are controlled by the
       options specified. The patterns are specified  by  the  -e  option,  -f
       option,	or  the	 pattern_list  operand. The pattern_list's value shall
       consist of one or more  patterns	 separated  by	<newline>s;  the  pat‐
       tern_file's  contents  shall consist of one or more patterns terminated
       by <newline>. By default, an input line shall be selected if  any  pat‐
       tern,  treated as an entire basic regular expression (BRE) as described
       in the Base Definitions volume of  IEEE Std 1003.1-2001,	 Section  9.3,
       Basic  Regular  Expressions, matches any part of the line excluding the
       terminating <newline>; a null BRE shall match every line.  By  default,
       each selected input line shall be written to the standard output.

       Regular expression matching shall be based on text lines. Since a <new‐
       line> separates or terminates patterns  (see  the  -e  and  -f  options
       below),	regular	 expressions  cannot  contain  a <newline>. Similarly,
       since patterns are matched against individual lines (excluding the ter‐
       minating	 <newline>s)  of  the  input, there is no way for a pattern to
       match a <newline> found in the input.

OPTIONS
       The grep utility shall  conform	to  the	 Base  Definitions  volume  of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -E     Match  using  extended  regular  expressions. Treat each pattern
	      specified as an ERE, as described in the Base Definitions volume
	      of  IEEE Std 1003.1-2001,	 Section 9.4, Extended Regular Expres‐
	      sions.  If any entire ERE pattern matches some part of an	 input
	      line  excluding  the  terminating	 <newline>,  the line shall be
	      matched.	A null ERE shall match every line.

       -F     Match using fixed strings. Treat each  pattern  specified	 as  a
	      string  instead  of  a regular expression. If an input line con‐
	      tains any of the patterns as a contiguous sequence of bytes, the
	      line shall be matched. A null string shall match every line.

       -c     Write only a count of selected lines to standard output.

       -e  pattern_list

	      Specify  one  or	more patterns to be used during the search for
	      input.  The application  shall  ensure  that  patterns  in  pat‐
	      tern_list	 are  separated	 by a <newline>. A null pattern can be
	      specified by two adjacent <newline>s in pattern_list. Unless the
	      -E or -F option is also specified, each pattern shall be treated
	      as a BRE,	 as  described	in  the	 Base  Definitions  volume  of
	      IEEE Std 1003.1-2001,  Section  9.3,  Basic Regular Expressions.
	      Multiple -e and -f options shall be accepted by the  grep	 util‐
	      ity.  All	 of the specified patterns shall be used when matching
	      lines, but the order of evaluation is unspecified.

       -f  pattern_file

	      Read one or more patterns from the file named  by	 the  pathname
	      pattern_file.  Patterns in pattern_file shall be terminated by a
	      <newline>. A null pattern can be specified by an empty  line  in
	      pattern_file. Unless the -E or -F option is also specified, each
	      pattern shall be treated as a BRE, as described in the Base Def‐
	      initions volume of IEEE Std 1003.1-2001, Section 9.3, Basic Reg‐
	      ular Expressions.

       -i     Perform pattern matching in searches without regard to case; see
	      the  Base	 Definitions  volume  of IEEE Std 1003.1-2001, Section
	      9.2, Regular Expression General Requirements.

       -l     (The letter ell.) Write  only  the  names	 of  files  containing
	      selected	lines  to  standard output. Pathnames shall be written
	      once per file searched. If the standard  input  is  searched,  a
	      pathname	of  "(standard	input)" shall be written, in the POSIX
	      locale. In other locales, "standard input" may  be  replaced  by
	      something more appropriate in those locales.

       -n     Precede  each  output  line  by  its relative line number in the
	      file, each file starting at line	1.  The	 line  number  counter
	      shall be reset for each file processed.

       -q     Quiet.  Nothing shall be written to the standard output, regard‐
	      less of matching lines. Exit with zero status if an  input  line
	      is selected.

       -s     Suppress	the  error messages ordinarily written for nonexistent
	      or unreadable files. Other error	messages  shall	 not  be  sup‐
	      pressed.

       -v     Select  lines not matching any of the specified patterns. If the
	      -v option is not specified, selected lines shall be  those  that
	      match any of the specified patterns.

       -x     Consider	only  input  lines that use all characters in the line
	      excluding the terminating <newline> to  match  an	 entire	 fixed
	      string or regular expression to be matching lines.

OPERANDS
       The following operands shall be supported:

       pattern_list
	      Specify  one  or	more patterns to be used during the search for
	      input.  This operand shall be treated as if it were specified as
	      -e pattern_list.

       file   A pathname of a file to be searched for the patterns. If no file
	      operands are specified, the standard input shall be used.

STDIN
       The standard input shall be used only if no file	 operands  are	speci‐
       fied. See the INPUT FILES section.

INPUT FILES
       The input files shall be text files.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of grep:

       LANG   Provide  a  default value for the internationalization variables
	      that are unset or null. (See  the	 Base  Definitions  volume  of
	      IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari‐
	      ables for the precedence of internationalization variables  used
	      to determine the values of locale categories.)

       LC_ALL If  set  to a non-empty string value, override the values of all
	      the other internationalization variables.

       LC_COLLATE

	      Determine the locale for the  behavior  of  ranges,  equivalence
	      classes,	and  multi-character collating elements within regular
	      expressions.

       LC_CTYPE
	      Determine the locale for	the  interpretation  of	 sequences  of
	      bytes  of	 text  data as characters (for example, single-byte as
	      opposed to multi-byte characters in arguments and	 input	files)
	      and  the	behavior  of  character classes within regular expres‐
	      sions.

       LC_MESSAGES
	      Determine the locale that should be used to  affect  the	format
	      and contents of diagnostic messages written to standard error.

       NLSPATH
	      Determine the location of message catalogs for the processing of
	      LC_MESSAGES .

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       If the -l option is in effect, and the -q option is not, the  following
       shall  be  written for each file containing at least one selected input
       line:

	      "%s\n", <file>

       Otherwise, if more than one file argument appears, and -q is not speci‐
       fied, the grep utility shall prefix each output line by:

	      "%s:", <file>

       The  remainder  of  each	 output line shall depend on the other options
       specified:

	* If the -c option is in effect, the remainder	of  each  output  line
	  shall contain:

	  "%d\n", <count>

	* Otherwise,  if  -c  is not in effect and the -n option is in effect,
	  the following shall be written to standard output:

	  "%d:", <line number>

	* Finally, the following shall be written to standard output:

	  "%s", <selected-line contents>

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

	0     One or more lines were selected.

	1     No lines were selected.

       >1     An error occurred.

CONSEQUENCES OF ERRORS
       If the -q option is specified, the exit status  shall  be  zero	if  an
       input  line  is	selected,  even	 if an error was detected.  Otherwise,
       default actions shall be performed.

       The following sections are informative.

APPLICATION USAGE
       Care should be taken when using characters  in  pattern_list  that  may
       also  be meaningful to the command interpreter. It is safest to enclose
       the entire pattern_list argument in single quotes:

	      '...'

       The -e pattern_list option has the same effect as the pattern_list  op‐
       erand,  but  is	useful when pattern_list begins with the hyphen delim‐
       iter. It is also useful when it is more convenient to provide  multiple
       patterns as separate arguments.

       Multiple	 -e  and -f options are accepted and grep uses all of the pat‐
       terns it is given while matching input text lines. (Note that the order
       of  evaluation  is  not	specified.  If	an implementation finds a null
       string as a pattern, it is allowed to use that pattern first,  matching
       every line, and effectively ignore any other patterns.)

       The  -q	option provides a means of easily determining whether or not a
       pattern (or string) exists in a group of files.	When searching several
       files,  it  provides  a performance improvement (because it can quit as
       soon as it finds the first match) and requires less care by the user in
       choosing the set of files to supply as arguments (because it exits zero
       if it finds a match even if grep detected an access or  read  error  on
       earlier file operands).

EXAMPLES
	1. To  find all uses of the word "Posix" (in any case) in file text.mm
	   and write with line numbers:

	   grep -i -n posix text.mm

	2. To find all empty lines in the standard input:

	   grep ^$

       or:

	      grep -v .

	3. Both of the following commands print all lines  containing  strings
	   "abc" or "def" or both:

	   grep -E 'abc|def'

	   grep -F 'abc
	   def'

	4. Both	 of  the  following  commands print all lines matching exactly
	   "abc" or "def" :

	   grep -E '^abc$|^def$'

	   grep -F -x 'abc
	   def'

RATIONALE
       This grep has been enhanced in an upwards-compatible way to provide the
       exact functionality of the historical egrep and fgrep commands as well.
       It was the clear intention of the standard  developers  to  consolidate
       the three greps into a single command.

       The  old	 egrep	and fgrep commands are likely to be supported for many
       years to come as implementation extensions, allowing historical	appli‐
       cations to operate unmodified.

       Historical implementations usually silently ignored all but one of mul‐
       tiply-specified -e and -f options, but were not consistent as to	 which
       specification was actually used.

       The  -b	option was omitted from the OPTIONS section because block num‐
       bers are implementation-defined.

       The System V restriction on using - to mean standard input was omitted.

       A definition of action taken when given a null BRE or ERE is specified.
       This is an error condition in some historical implementations.

       The  -l	option previously indicated that its use was undefined when no
       files were explicitly named. This behavior was historical and placed an
       unnecessary   restriction  on  future  implementations.	 It  has  been
       removed.

       The historical BSD grep -s option  practice  is	easily	duplicated  by
       redirecting  standard  output to /dev/null. The -s option required here
       is from System V.

       The -x option, historically available only  with	 fgrep,	 is  available
       here for all of the non-obsolescent versions.

FUTURE DIRECTIONS
       None.

SEE ALSO
       sed

COPYRIGHT
       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003	by  the	 Institute  of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained	online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			      GREP(1P)
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