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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 pat-
       terns; 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  pattern_file's
       contents  shall  consist  of  one or more patterns terminated by <newline>. 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  terminating  <new-
       line>;  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
       terminating  <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 applica-
              tion 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.   Pat-
              terns  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 Defini-
              tions volume of IEEE Std 1003.1-2001, Section 9.3, Basic Regular Expressions.

       -i     Perform pattern matching in searches without regard to case; see the  Base  Defini-
              tions  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  stan-
              dard  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 appro-
              priate in those locales.

       -n     Precede each output line by its relative line number in the file, each file  start-
              ing 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  termi-
              nating <newline> to match an entire fixed string or regular expression to be match-
              ing 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 spec-
              ified, 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, Inter-
              nationalization 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  interna-
              tionalization 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 argu-
              ments 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 diag-
              nostic 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 specified, the grep util-
       ity 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 sin-
       gle 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 delimiter. It is also useful when it is more con-
       venient 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  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 op-
       erands).

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  functional-
       ity  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 applications 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  implementa-
       tion-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  explic-
       itly  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                            2003                                      GREP(1P)


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