grep.1

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.\"	@(#)grep.1	8.3 (Berkeley) 4/18/94
.\"
.Dd April 18, 1994
.Dt GREP 1
.Os
.Sh NAME
.Nm grep
.Nd file pattern searcher
.Sh SYNOPSIS
.Nm grep
.Op Fl bchilnosvw
.Op Fl e Ar pattern
.Op Ar
.Nm egrep
.Op Fl bchilnosv
.Op Fl e Ar pattern
.Op Fl f Ar pattern_file
.Op Ar
.Nm fgrep
.Op Fl bchilnosvx
.Op Fl e Ar pattern
.Op Fl f Ar pattern_file
.Op Ar
.Sh DESCRIPTION
The
.Nm grep
utilities search the given input files selecting lines
which match one or more patterns; the type of patterns is controlled
by the options specified.
By default, a pattern
matches an input line if any regular expression (RE) in the
pattern matches the input line without its trailing <new-line>.
A null RE matches every line.
Each input line that matches at
least one of the patterns is written to the standard output.
.Pp
For simple patterns or
.Xr ex 1
or
.Xr ed 1
style regular expressions, the
.Nm grep
utility is used.
The
.Nm egrep
utility
can handle extended regular expressions and
embedded <newline>s in patterns.
The
.Nm fgrep
utility is quick but can handle only fixed strings.
A fixed string
is a string of characters,
each character
is matched only by itself.
The pattern
value can consist of multiple lines with
embedded <newline>s.
In this case, the <newline>s
act as alternation characters, allowing any of the
pattern lines to match a portion of the input.
.Pp
The following options are available:
.Pp
.Bl -tag -width indent
.It Fl b
The block number on the disk in which a matched pattern is located
is displayed in front of the respective matched line.
.It Fl c
Only a count of selected lines is written to standard
output.
.It Fl e Ar expression 
Specify a pattern used during the search of the
input.
Multiple
.Fl e
options can be used to specify
multiple patterns; an input line is selected if it
matches any of the specified patterns.
.It Fl f Ar pattern_file 
The pattern is read from the file named by the
pathname pattern_file.
Trailing newlines
in the pattern_file are ignored.
.Pf ( Nm Egrep
and
.Nm fgrep
only).
.It Fl h
Never print filename headers with output lines.
.It Fl i
The case of letters is ignored in making comparisons \- that is, upper and
lower case are considered identical.
.It Fl l
Only the names of files containing selected lines
are written to standard output.
Pathnames are
listed once per file searched.
If the standard
input is searched, the pathname
.Sq Fl
is written.
.It Fl n
Each output line is preceded by its relative line
number in the file; each file starting at line 1.
The line number counter is reset for each file processed.
This option is ignored if
.Fl c ,
.Fl l ,
or
.Fl s
is
specified.
.It Fl o
Always print filename headers with output lines.
.It Fl s
Silent mode.  Nothing is printed (except error messages).
This is useful for checking the error status.
.It Fl v
Selected lines are those
.Em not
matching the specified
patterns.
.It Fl x
Only input lines selected against an entire fixed
string or regular expression are considered to be
matching lines.
.Pf ( Nm Fgrep
only).
.It Fl w
The expression is searched for as a word
(as if surrounded by `\e<' and `\e>', see
.Xr ex  1  . )
.Pf ( Nm Grep
only)
.Pp
.El
If no file arguments are specified, the
standard input is used.
.Pp
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 >1
An error occurred.
.El
.Sh EXTENDED REGULAR EXPRESSIONS
The following characters are interpreted by
.Nm egrep :
.Pp
.Bl -tag -width flag -compact
.It Cm \&$
Align the match from the end of the line.
.It Cm \&^
Align the match from the beginning of the line.
.It Cm \&|
Add another pattern (see example below).
.It Cm \&?
Match 1 or less sequential repetitions of the pattern.
.It Cm \&+
Match 1 or more sequential repetitions of the pattern.
.It Cm \&*
Match 0 or more sequential repetitions of the pattern.
.It Cm \&[]
Match any single character or range of characters
enclosed in the brackets.
.It Cm \&\e
Escape special characters which have meaning to
.Nm egrep ,
the set of {$,.,^,[,],|,?,+,*,(,)}.
.El
.Sh EXAMPLES
To find all occurrences of the word 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'
.Pp
The apostrophes assure the entire expression is evaluated by
.Nm grep
instead of by the
users shell.
The carat or hat
.Ql Li \&^
means
.Em from the beginning of a line ,
and the
.Ql Li \&\e
escapes the
.Ql Li \&.
which would otherwise match any character.
.Pp
A simple example of an extended regular expression:
.Pp
.Dl egrep '19|20|25' calendar
.Pp
Peruses the file calendar looking for either 19, 20
or 25.
.Sh SEE ALSO
.Xr ed 1 ,
.Xr ex 1 ,
.Xr sed 1
.Sh HISTORY
The
.Nm grep
command appeared in
.At v6 .
.Sh BUGS
Lines are limited to 256 characters; longer lines are truncated.