266 lines
6.7 KiB
Groff
266 lines
6.7 KiB
Groff
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.TH GREP 1 "1988 December 13" "GNU Project"
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.UC 4
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.SH NAME
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grep, egrep \- print lines matching a regular expression
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.SH SYNOPSIS
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.B grep
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[
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.B \-CVbchilnsvwx
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] [
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.BI \- num
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] [
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.B \-AB
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.I num
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] [ [
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.B \-e
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]
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.I expr
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.B \-f
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.I file
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] [
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.I "files ..."
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]
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.SH DESCRIPTION
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.I Grep
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searches the files listed in the arguments (or standard
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input if no files are given) for all lines that contain a match for
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the given
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.IR expr .
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If any lines match, they are printed.
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.PP
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Also, if any matches were found,
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.I grep
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will exit with a status of 0, but if no matches were found it will exit
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with a status of 1. This is useful for building shell scripts that
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use
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.I grep
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as a condition for, for example, the
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.I if
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statement.
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.PP
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When invoked as
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.I egrep
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the syntax of the
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.I expr
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is slightly different; See below.
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.br
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.SH "REGULAR EXPRESSIONS"
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.RS 2.5i
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.ta 1i; 2i
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.sp
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.ti -2.0i
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(grep) (egrep) (explanation)
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.sp
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.ti -2.0i
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\fIc\fP \fIc\fP a single (non-meta) character matches itself.
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.sp
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.ti -2.0i
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\&. . matches any single character except newline.
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.sp
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.ti -2.0i
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\\? ? postfix operator; preceeding item is optional.
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.sp
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.ti -2.0i
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\(** \(** postfix operator; preceeding item 0 or
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more times.
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.sp
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.ti -2.0i
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\\+ + postfix operator; preceeding item 1 or
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more times.
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.sp
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.ti -2.0i
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\\| | infix operator; matches either
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argument.
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.sp
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.ti -2.0i
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^ ^ matches the empty string at the beginning of a line.
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.sp
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.ti -2.0i
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$ $ matches the empty string at the end of a line.
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.sp
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.ti -2.0i
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\\< \\< matches the empty string at the beginning of a word.
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.sp
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.ti -2.0i
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\\> \\> matches the empty string at the end of a word.
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.sp
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.ti -2.0i
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[\fIchars\fP] [\fIchars\fP] match any character in the given class; if the
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first character after [ is ^, match any character
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not in the given class; a range of characters may
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be specified by \fIfirst\-last\fP; for example, \\W
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(below) is equivalent to the class [^A\-Za\-z0\-9]
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.sp
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.ti -2.0i
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\\( \\) ( ) parentheses are used to override operator precedence.
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.sp
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.ti -2.0i
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\\\fIdigit\fP \\\fIdigit\fP \\\fIn\fP matches a repeat of the text
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matched earlier in the regexp by the subexpression inside the nth
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opening parenthesis.
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.sp
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.ti -2.0i
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\\ \\ any special character may be preceded
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by a backslash to match it literally.
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.sp
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.ti -2.0i
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(the following are for compatibility with GNU Emacs)
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.sp
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.ti -2.0i
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\\b \\b matches the empty string at the edge of a word.
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.sp
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.ti -2.0i
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\\B \\B matches the empty string if not at the edge of a word.
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.sp
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.ti -2.0i
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\\w \\w matches word-constituent characters (letters & digits).
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.sp
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.ti -2.0i
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\\W \\W matches characters that are not word-constituent.
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.RE
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.PP
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Operator precedence is (highest to lowest) ?, \(**, and +, concatenation,
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and finally |. All other constructs are syntactically identical to
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normal characters. For the truly interested, the file dfa.c describes
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(and implements) the exact grammar understood by the parser.
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.SH OPTIONS
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.TP
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.BI \-A " num"
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print <num> lines of context after every matching line
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.TP
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.BI \-B " num"
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print
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.I num
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lines of context before every matching line
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.TP
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.B \-C
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print 2 lines of context on each side of every match
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.TP
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.BI \- num
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print
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.I num
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lines of context on each side of every match
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.TP
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.B \-V
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print the version number on the diagnostic output
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.TP
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.B \-b
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print every match preceded by its byte offset
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.TP
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.B \-c
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print a total count of matching lines only
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.TP
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.BI \-e " expr"
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search for
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.IR expr ;
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useful if
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.I expr
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begins with \-
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.TP
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.BI \-f " file"
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search for the expression contained in
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.I file
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.TP
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.B \-h
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don't display filenames on matches
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.TP
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.B \-i
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ignore case difference when comparing strings
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.TP
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.B \-l
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list files containing matches only
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.TP
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.B \-n
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print each match preceded by its line number
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.TP
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.B \-s
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run silently producing no output except error messages
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.TP
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.B \-v
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print only lines that contain no matches for the <expr>
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.TP
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.B \-w
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print only lines where the match is a complete word
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.TP
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.B \-x
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print only lines where the match is a whole line
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.SH "SEE ALSO"
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emacs(1), ed(1), sh(1),
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.I "GNU Emacs Manual"
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.SH INCOMPATIBILITIES
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The following incompatibilities with UNIX
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.I grep
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exist:
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.PP
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.RS 0.5i
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The context-dependent meaning of \(** is not quite the same (grep only).
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.PP
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.B \-b
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prints a byte offset instead of a block offset.
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.PP
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The {\fIm,n\fP} construct of System V grep is not implemented.
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.PP
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.SH BUGS
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GNU \fIe?grep\fP has been thoroughly debugged and tested by several people
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over a period of several months; we think it's a reliable beast or we
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wouldn't distribute it. If by some fluke of the universe you discover
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a bug, send a detailed description (including options, regular
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expressions, and a copy of an input file that can reproduce it) to me,
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mike@wheaties.ai.mit.edu.
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.PP
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There is also a newsgroup, gnu.utils.bug, for reporting FSF utility
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programs' bugs and fixes; but before reporting something as a bug,
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please try to be sure that it really is a bug, not a misunderstanding
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or a deliberate feature. Also, include the version number of the
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utility program you are running in \fIevery\fR bug report that you
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send in. Please do not send anything but bug reports to this
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newsgroup.
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.PP
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.SH AVAILABILITY
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.PP
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GNU
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.I grep
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is free; anyone may redistribute copies of
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.I grep
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to
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anyone under the terms stated in the
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GNU General Public License,
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a copy of which may be found in each copy of
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.IR "GNU Emacs" .
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See also the comment at the beginning of the source code file grep.c.
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.PP
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Copies of GNU
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.I grep
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may sometimes be received packaged with distributions of Unix systems,
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but it is never included in the scope of any license covering those
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systems. Such inclusion violates the terms on which distribution
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is permitted. In fact, the primary purpose of the General Public
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License is to prohibit anyone from attaching any other restrictions
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to redistribution of any of the Free Software Foundation programs.
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.SH AUTHORS
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Mike Haertel wrote the deterministic regexp code and the bulk
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of the program.
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.PP
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James A. Woods is responsible for the hybridized search strategy
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of using Boyer-Moore-Gosper fixed-string search as a filter
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before calling the general regexp matcher.
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.PP
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Arthur David Olson contributed code that finds fixed strings for
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the aforementioned BMG search for a large class of regexps.
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.PP
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Richard Stallman wrote the backtracking regexp matcher that is
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used for \\\fIdigit\fP backreferences, as well as the getopt that
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is provided for 4.2BSD sites. The backtracking matcher was
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originally written for GNU Emacs.
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.PP
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D. A. Gwyn wrote the C alloca emulation that is provided so
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System V machines can run this program. (Alloca is used only
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by RMS' backtracking matcher, and then only rarely, so there
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is no loss if your machine doesn't have a "real" alloca.)
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.PP
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Scott Anderson and Henry Spencer designed the regression tests
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used in the "regress" script.
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.PP
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Paul Placeway wrote the original version of this manual page.
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