freebsd-src/usr.bin/grep/grep.1

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.Dd December 18, 2022
.Dt GREP 1
.Os
.Sh NAME
.Nm grep ,
.Nm egrep ,
.Nm fgrep ,
.Nm rgrep
.Nd file pattern searcher
.Sh SYNOPSIS
.Nm grep
.Bk -words
.Op Fl abcdDEFGHhIiLlmnOopqRSsUVvwxz
.Op Fl A Ar num
.Op Fl B Ar num
.Op Fl C Ar num
.Op Fl e Ar pattern
.Op Fl f Ar file
.Op Fl Fl binary-files= Ns Ar value
.Op Fl Fl color Ns Op Cm = Ns Ar when
.Op Fl Fl colour Ns Op Cm = Ns Ar when
.Op Fl Fl context= Ns Ar num
.Op Fl Fl label
.Op Fl Fl line-buffered
.Op Fl Fl null
.Op Ar pattern
.Op Ar
.Ek
.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
The following options are available:
.Bl -tag -width indent
.It Fl A Ar num , Fl Fl after-context= 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 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 Ar num , Fl Fl context= Ns Ar num
Print
.Ar num
lines of leading and trailing context surrounding each match.
See also the
.Fl A
and
.Fl B
options.
.It Fl c , Fl Fl count
Only a count of selected lines is written to standard output.
.It Fl Fl colour= Ns Oo Ar when Oc , Fl Fl color= Ns Oo Ar when Oc
Mark up the matching text with the expression stored in the
.Ev GREP_COLOR
environment variable.
The possible values of
.Ar when
are
.Dq Cm never ,
.Dq Cm always
and
.Dq Cm auto .
.It Fl D Ar action , Fl Fl devices= Ns Ar action
Specify the demanded
.Ar action
for devices, FIFOs and sockets.
The default
.Ar action
is
.Dq Cm read ,
which means, that they are read as if they were normal files.
If the
.Ar action
is set to
.Dq Cm skip ,
devices are silently skipped.
.It Fl d Ar action , Fl Fl directories= Ns Ar action
Specify the demanded
.Ar action
for directories.
It is
.Dq Cm read
by default, which means that the directories
are read in the same manner as normal files.
Other possible values are
.Dq Cm skip
to silently ignore the directories, and
.Dq Cm 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 Ar pattern
Specify a
.Ar 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
.Ar pattern
begins with a dash
.Pq Sq - .
.It Fl Fl exclude Ar pattern
If specified, it excludes files matching the given
filename
.Ar pattern
from the search.
Note that
.Fl Fl exclude
and
.Fl Fl include
patterns are processed in the order given.
If a name matches multiple patterns, the latest matching rule wins.
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 Ar pattern
If
.Fl R
is specified, it excludes directories matching the
given filename
.Ar pattern
from the search.
Note that
.Fl Fl exclude-dir
and
.Fl Fl include-dir
patterns are processed in the order given.
If a name matches multiple patterns, the latest matching rule wins.
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 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 the
.Dq Fl Fl binary-files= Ns Cm 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 Ar pattern
If specified, only files matching the given filename
.Ar pattern
are searched.
Note that
.Fl Fl include
and
.Fl Fl exclude
patterns are processed in the order given.
If a name matches multiple patterns, the latest matching rule wins.
Patterns are matched to the full path specified,
not only to the filename component.
.It Fl Fl include-dir Ar pattern
If
.Fl R
is specified, only directories matching the given filename
.Ar pattern
are searched.
Note that
.Fl Fl include-dir
and
.Fl Fl exclude-dir
patterns are processed in the order given.
If a name matches multiple patterns, the latest matching rule wins.
.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 unless a
.Fl Fl label
is specified.
.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 unless a
.Fl Fl label
is specified.
.It Fl Fl label
Label to use in place of
.Dq (standard input)
for a file name where a file name would normally be printed.
This option applies to
.Fl H ,
.Fl L ,
and
.Fl l .
.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 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 Fl null
Prints a zero-byte after the file name.
.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.
(i.e., force
.Nm grep
to behave as
.Nm rgrep ) .
.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 u
This option has no effect and is provided only for compatibility with GNU grep.
.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 ) .
This option has no effect if
.Fl x
is also specified.
.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-data
Treat input and output data as sequences of lines terminated by a
zero-byte instead of a newline.
.It Fl Fl binary-files= Ns Ar value
Controls searching and printing of binary files.
Options are:
.Bl -tag -compact -width "binary (default)"
.It Cm binary No (default)
Search binary files but do not print them.
.It Cm without-match
Do not search binary files.
.It Cm text
Treat all files as text.
.El
.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.
.El
.Pp
If no file arguments are specified, the standard input is used.
Additionally,
.Dq Cm -
may be used in place of a file name, anywhere that a file name is accepted, to
read from standard input.
This includes both
.Fl f
and file arguments.
.Sh ENVIRONMENT
The following environment variables affect the execution of
.Nm :
.Bl -tag -width "GREP_OPTIONS"
.It Ev GREP_COLOR
This variable specifies the color used to highlight matched (non-empty) text.
.It Ev GREP_OPTIONS
This variable specifies default options
to be placed in front of any explicit options.
It may cause problems with portable scripts.
.It Ev TERM
This variable specifies the type name of the terminal, console or display-device
type to be used.
See
.Xr term 7 .
.El
.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
.Bl -dash
.It
Find all occurrences of the pattern
.Sq patricia
in a file:
.Pp
.Dl $ grep 'patricia' myfile
.It
Same as above but looking only for complete words:
.Pp
.Dl $ grep -w 'patricia' myfile
.It
Count occurrences of the exact pattern
.Sq FOO
:
.Pp
.Dl $ grep -c FOO myfile
.It
Same as above but ignoring case:
.Pp
.Dl $ grep -c -i FOO myfile
.It
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.
.It
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
.It
Peruse the file
.Sq calendar
looking for either 19, 20, or 25 using extended regular expressions:
.Pp
.Dl $ egrep '19|20|25' calendar
.It
Show matching lines and the name of the
.Sq *.h
files which contain the pattern
.Sq FIXME .
Do the search recursively from the
.Pa /usr/src/sys/arm
directory
.Pp
.Dl $ grep -H -R FIXME --include="*.h" /usr/src/sys/arm/
.It
Same as above but show only the name of the matching file:
.Pp
.Dl $ grep -l -R FIXME --include="*.h" /usr/src/sys/arm/
.It
Show lines containing the text
.Sq foo .
The matching part of the output is colored and every line is prefixed with
the line number and the offset in the file for those lines that matched.
.Pp
.Dl $ grep -b --colour -n foo myfile
.It
Show lines that match the extended regular expression patterns read from the
standard input:
.Pp
.Dl $ echo -e 'Free\enBSD\enAll.*reserved' | grep -E -f - myfile
.It
Show lines from the output of the
.Xr pciconf 8
command matching the specified extended regular expression along with
three lines of leading context and one line of trailing context:
.Pp
.Dl $ pciconf -lv | grep -B3 -A1 -E 'class.*=.*storage'
.It
Suppress any output and use the exit status to show an appropriate message:
.Pp
.Dl $ grep -q foo myfile && echo File matches
.El
.Sh SEE ALSO
.Xr ed 1 ,
.Xr ex 1 ,
.Xr sed 1 ,
.Xr zgrep 1 ,
.Xr re_format 7
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification.
.Pp
The flags
.Op Fl AaBbCDdGHhILmopRSUVw
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 .