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 correspond-
       ing 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 con-
       sist of one or more patterns separated by <newline>s; the pattern_file's contents shall consist of one or more patterns terminated by <new-
       line>.  By default, an input line shall be selected if any pattern, 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  termi-
       nating <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 <newline> 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 Expressions.	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 contains 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 pattern_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 utility. 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 <new-
	      line>.  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 Definitions volume of IEEE Std 1003.1-2001, Section 9.3, Basic  Regular  Expres-
	      sions.

       -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, regardless 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 suppressed.

       -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 specified. 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 Variables 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 expres-
	      sions.

       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 expressions.

       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
", <file>

       Otherwise, if more than one file argument appears, and -q is not specified, 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
", <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 operand, 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 patterns 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 sev-
       eral 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 multiply-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 numbers 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 Technol-
       ogy -- 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)