Provided by: manpages-posix_2.16-1_all bug

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  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
       <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
       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
              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 <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
              Definitions 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
              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 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
              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\n", <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\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 operand, but is  useful
       when  pattern_list  begins  with  the  hyphen delimiter. 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  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 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
       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 .