.\"	$NetBSD: grep.1,v 1.4 2012/04/08 22:00:38 wiz Exp $
.\"	$FreeBSD: head/usr.bin/grep/grep.1 210652 2010-07-30 14:05:20Z joel $
.\"	$OpenBSD: grep.1,v 1.38 2010/04/05 06:30:59 jmc Exp $
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.\"	@(#)grep.1	8.3 (Berkeley) 4/18/94
.\"
.Dd April 19, 2011
.Dt GREP 1
.Os
.Sh NAME
.Nm grep , egrep , fgrep ,
.Nm zgrep , zegrep , zfgrep
.Nd file pattern searcher
.Sh SYNOPSIS
.Nm grep
.Op Fl abcdDEFGHhIiJLlmnOopqRSsUVvwxZz
.Op Fl A Ar num
.Op Fl B Ar num
.Op Fl C Ns Op Ar num
.Op Fl e Ar pattern
.Op Fl f Ar file
.Op Fl Fl binary-files Ns = Ns Ar value
.Op Fl Fl color Ns Op = Ns Ar when
.Op Fl Fl colour Ns Op = Ns Ar when
.Op Fl Fl context Ns Op = Ns Ar num
.Op Fl Fl decompress
.Op Fl Fl label
.Op Fl Fl line-buffered
.Op Ar pattern
.Op Ar
.Sh DESCRIPTION
The
.Nm grep
utility searches any given input files,
selecting lines that match one or more patterns.
By default, a pattern matches an input line if the regular expression
(RE) in the pattern matches the input line
without its trailing newline.
An empty expression matches every line.
Each input line that matches at least one of the patterns is written
to the standard output.
.Pp
.Nm grep
is used for simple patterns and
basic regular expressions
.Pq BREs ;
.Nm egrep
can handle extended regular expressions
.Pq EREs .
See
.Xr re_format 7
for more information on regular expressions.
.Nm fgrep
is quicker than both
.Nm grep
and
.Nm egrep ,
but can only handle fixed patterns
(i.e. it does not interpret regular expressions).
Patterns may consist of one or more lines,
allowing any of the pattern lines to match a portion of the input.
.Pp
.Nm zgrep ,
.Nm zegrep ,
and
.Nm zfgrep
act like
.Nm grep ,
.Nm egrep ,
and
.Nm fgrep ,
respectively, but accept input files compressed with the
.Xr compress 1
or
.Xr gzip 1
compression utilities.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl A Ar num , Fl Fl after-context Ns = Ns Ar num
Print
.Ar num
lines of trailing context after each match.
See also the
.Fl B
and
.Fl C
options.
.It Fl a , Fl Fl text
Treat all files as ASCII text.
Normally
.Nm
will simply print
.Dq Binary file ... matches
if files contain binary characters.
Use of this option forces
.Nm
to output lines matching the specified pattern.
.It Fl B Ar num , Fl Fl before-context Ns = Ns Ar num
Print
.Ar num
lines of leading context before each match.
See also the
.Fl A
and
.Fl C
options.
.It Fl b , Fl Fl byte-offset
The offset in bytes of a matched pattern is
displayed in front of the respective matched line.
.It Fl C Ns Op Ar num , Fl Fl context Ns = Ns Ar num
Print
.Ar num
lines of leading and trailing context surrounding each match.
The default is 2 and is equivalent to
.Fl A
.Ar 2
.Fl B
.Ar 2 .
Note:
no whitespace may be given between the option and its argument.
.It Fl c , Fl Fl count
Only a count of selected lines is written to standard output.
.It Fl Fl colour Ns = Ns Op Ar when , Fl Fl color Ns = Ns Op Ar when
Mark up the matching text with the expression stored in
.Ev GREP_COLOR
environment variable.
The possible values of when can be `never', `always' or `auto'.
.It Fl D Ar action , Fl Fl devices Ns = Ns Ar action
Specify the demanded action for devices, FIFOs and sockets.
The default action is `read', which means, that they are read
as if they were normal files.
If the action is set to `skip', devices will be silently skipped.
.It Fl d Ar action , Fl Fl directories Ns = Ns Ar action
Specify the demanded action for directories.
It is `read' by default, which means that the directories
are read in the same manner as normal files.
Other possible values are `skip' to silently ignore the
directories, and `recurse' to read them recursively, which
has the same effect as the
.Fl R
and
.Fl r
option.
.It Fl E , Fl Fl extended-regexp
Interpret
.Ar pattern
as an extended regular expression
(i.e. force
.Nm grep
to behave as
.Nm egrep ) .
.It Fl e Ar pattern , Fl Fl regexp Ns = Ns Ar pattern
Specify a pattern used during the search of the input:
an input line is selected if it matches any of the specified patterns.
This option is most useful when multiple
.Fl e
options are used to specify multiple patterns,
or when a pattern begins with a dash
.Pq Sq - .
.It Fl Fl exclude
If specified, it excludes files matching the given
filename pattern from the search.
Note that
.Fl Fl exclude
patterns take priority over
.Fl Fl include
patterns, and if no
.Fl Fl include
pattern is specified, all files are searched that are
not excluded.
Patterns are matched to the full path specified,
not only to the filename component.
.It Fl Fl exclude-dir
If
.Fl R
is specified, it excludes directories matching the
given filename pattern from the search.
Note that
.Fl Fl exclude-dir
patterns take priority over
.Fl Fl include-dir
patterns, and if no
.Fl Fl include-dir
pattern is specified, all directories are searched that are
not excluded.
.It Fl F , Fl Fl fixed-strings
Interpret
.Ar pattern
as a set of fixed strings
(i.e. force
.Nm grep
to behave as
.Nm fgrep ) .
.It Fl f Ar file , Fl Fl file Ns = Ns Ar file
Read one or more newline separated patterns from
.Ar file .
Empty pattern lines match every input line.
Newlines are not considered part of a pattern.
If
.Ar file
is empty, nothing is matched.
.It Fl G , Fl Fl basic-regexp
Interpret
.Ar pattern
as a basic regular expression
(i.e. force
.Nm grep
to behave as traditional
.Nm grep ) .
.It Fl H
Always print filename headers with output lines.
.It Fl h , Fl Fl no-filename
Never print filename headers
.Pq i.e. filenames
with output lines.
.It Fl Fl help
Print a brief help message.
.It Fl I
Ignore binary files.
This option is equivalent to
.Fl Fl binary-file Ns = Ns Ar without-match
option.
.It Fl i , Fl Fl ignore-case
Perform case insensitive matching.
By default,
.Nm grep
is case sensitive.
.It Fl Fl include
If specified, only files matching the
given filename pattern are searched.
Note that
.Fl Fl exclude
patterns take priority over
.Fl Fl include
patterns.
Patterns are matched to the full path specified,
not only to the filename component.
.It Fl Fl include-dir
If
.Fl R
is specified, only directories matching the
given filename pattern are searched.
Note that
.Fl Fl exclude-dir
patterns take priority over
.Fl Fl include-dir
patterns.
.It Fl J, Fl Fl bz2decompress
Decompress the
.Xr bzip2 1
compressed file before looking for the text.
.It Fl L , Fl Fl files-without-match
Only the names of files not containing selected lines are written to
standard output.
Pathnames are listed once per file searched.
If the standard input is searched, the string
.Dq (standard input)
is written.
.It Fl l , Fl Fl files-with-matches
Only the names of files containing selected lines are written to
standard output.
.Nm grep
will only search a file until a match has been found,
making searches potentially less expensive.
Pathnames are listed once per file searched.
If the standard input is searched, the string
.Dq (standard input)
is written.
.It Fl Fl mmap
Use
.Xr mmap 2
instead of
.Xr read 2
to read input, which can result in better performance under some
circumstances but can cause undefined behaviour.
.It Fl m Ar num, Fl Fl max-count Ns = Ns Ar num
Stop reading the file after
.Ar num
matches.
.It Fl n , Fl Fl line-number
Each output line is preceded by its relative line number in the file,
starting at line 1.
The line number counter is reset for each file processed.
This option is ignored if
.Fl c ,
.Fl L ,
.Fl l ,
or
.Fl q
is
specified.
.It Fl O
If
.Fl R
is specified, follow symbolic links only if they were explicitly listed
on the command line.
The default is not to follow symbolic links.
.It Fl o, Fl Fl only-matching
Prints only the matching part of the lines.
.It Fl p
If
.Fl R
is specified, no symbolic links are followed.
This is the default.
.It Fl q , Fl Fl quiet , Fl Fl silent
Quiet mode:
suppress normal output.
.Nm grep
will only search a file until a match has been found,
making searches potentially less expensive.
.It Fl R , Fl r , Fl Fl recursive
Recursively search subdirectories listed.
.It Fl S
If
.Fl R
is specified, all symbolic links are followed.
The default is not to follow symbolic links.
.It Fl s , Fl Fl no-messages
Silent mode.
Nonexistent and unreadable files are ignored
(i.e. their error messages are suppressed).
.It Fl U , Fl Fl binary
Search binary files, but do not attempt to print them.
.It Fl V , Fl Fl version
Display version information and exit.
.It Fl v , Fl Fl invert-match
Selected lines are those
.Em not
matching any of the specified patterns.
.It Fl w , Fl Fl word-regexp
The expression is searched for as a word (as if surrounded by
.Sq [[:<:]]
and
.Sq [[:>:]] ;
see
.Xr re_format 7 ) .
.It Fl x , Fl Fl line-regexp
Only input lines selected against an entire fixed string or regular
expression are considered to be matching lines.
.It Fl y
Equivalent to
.Fl i .
Obsoleted.
.It Fl Z , Fl Fl null
Prints a zero-byte after the file name.
.It Fl z , Fl Fl null-data
Use the zero byte (ASCII NUL) as line separator.
.It Fl Fl binary-files Ns = Ns Ar value
Controls searching and printing of binary files.
Options are
.Ar binary ,
the default: search binary files but do not print them;
.Ar without-match :
do not search binary files;
and
.Ar text :
treat all files as text.
.It Fl Fl decompress
Detect input files compressed with
.Xr bzip2 1
or
.Xr gzip 1
and decompress them dynamically.
This makes
.Nm grep
behave like
.Nm zgrep .
.It Fl Fl line-buffered
Force output to be line buffered.
By default, output is line buffered when standard output is a terminal
and block buffered otherwise.
.Pp
.El
If no file arguments are specified, the standard input is used.
.Sh EXIT STATUS
The
.Nm grep
utility exits with one of the following values:
.Pp
.Bl -tag -width flag -compact
.It Li 0
One or more lines were selected.
.It Li 1
No lines were selected.
.It Li \*(Gt1
An error occurred.
.El
.Sh EXAMPLES
To find all occurrences of the word
.Sq patricia
in a file:
.Pp
.Dl $ grep 'patricia' myfile
.Pp
To find all occurrences of the pattern
.Ql .Pp
at the beginning of a line:
.Pp
.Dl $ grep '^\e.Pp' myfile
.Pp
The apostrophes ensure the entire expression is evaluated by
.Nm grep
instead of by the user's shell.
The caret
.Ql ^
matches the null string at the beginning of a line,
and the
.Ql \e
escapes the
.Ql \&. ,
which would otherwise match any character.
.Pp
To find all lines in a file which do not contain the words
.Sq foo
or
.Sq bar :
.Pp
.Dl $ grep -v -e 'foo' -e 'bar' myfile
.Pp
A simple example of an extended regular expression:
.Pp
.Dl $ egrep '19|20|25' calendar
.Pp
Peruses the file
.Sq calendar
looking for either 19, 20, or 25.
.Sh SEE ALSO
.Xr ed 1 ,
.Xr ex 1 ,
.Xr gzip 1 ,
.Xr sed 1 ,
.Xr re_format 7
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification.
.Pp
The flags
.Op Fl AaBbCDdGHhIJLmoPRSUVwZ
are extensions to that specification, and the behaviour of the
.Fl f
flag when used with an empty pattern file is left undefined.
.Pp
All long options are provided for compatibility with
GNU versions of this utility.
.Pp
Historic versions of the
.Nm grep
utility also supported the flags
.Op Fl ruy .
This implementation supports those options;
however, their use is strongly discouraged.
.Sh HISTORY
The
.Nm grep
command first appeared in
.At v6 .