377 lines
8.2 KiB
Groff
377 lines
8.2 KiB
Groff
.\" $Id: grep.1,v 1.3 1993/08/02 17:41:27 mycroft Exp $ -*- nroff -*-
|
|
.TH GREP 1 "1992 September 10" "GNU Project"
|
|
.SH NAME
|
|
grep, egrep, fgrep \- print lines matching a pattern
|
|
.SH SYNOPOSIS
|
|
.B grep
|
|
[
|
|
.BR \- [[ AB "] ]\c"
|
|
.I "num"
|
|
]
|
|
[
|
|
.BR \- [ CEFGVBchilnsvwx ]
|
|
]
|
|
[
|
|
.B \-e
|
|
]
|
|
.I pattern
|
|
|
|
|
.BI \-f file
|
|
] [
|
|
.I files...
|
|
]
|
|
.SH DESCRIPTION
|
|
.PP
|
|
.B Grep
|
|
searches the named input
|
|
.I files
|
|
(or standard input if no files are named, or
|
|
the file name
|
|
.B \-
|
|
is given)
|
|
for lines containing a match to the given
|
|
.IR pattern .
|
|
By default,
|
|
.B grep
|
|
prints the matching lines.
|
|
.PP
|
|
There are three major variants of
|
|
.BR grep ,
|
|
controlled by the following options.
|
|
.PD 0
|
|
.TP
|
|
.B \-G
|
|
Interpret
|
|
.I pattern
|
|
as a basic regular expression (see below). This is the default.
|
|
.TP
|
|
.B \-E
|
|
Interpret
|
|
.I pattern
|
|
as an extended regular expression (see below).
|
|
.TP
|
|
.B \-F
|
|
Interpret
|
|
.I pattern
|
|
as a list of fixed strings, separated by newlines,
|
|
any of which is to be matched.
|
|
.LP
|
|
In addition, two variant programs
|
|
.B egrep
|
|
and
|
|
.B fgrep
|
|
are available.
|
|
.B Egrep
|
|
is similiar (but not identical) to
|
|
.BR "grep\ \-E" ,
|
|
and is compatible with the historical Unix
|
|
.BR egrep .
|
|
.B Fgrep
|
|
is the same as
|
|
.BR "grep\ \-F" .
|
|
.PD
|
|
.LP
|
|
All variants of
|
|
.B grep
|
|
understand the following options:
|
|
.PD 0
|
|
.TP
|
|
.BI \- num
|
|
Matches will be printed with
|
|
.I num
|
|
lines of leading and trailing context. However,
|
|
.B grep
|
|
will never print any given line more than once.
|
|
.TP
|
|
.BI \-A " num"
|
|
Print
|
|
.I num
|
|
lines of trailing context after matching lines.
|
|
.TP
|
|
.BI \-B " num"
|
|
Print
|
|
.I num
|
|
lines of leading context before matching lines.
|
|
.TP
|
|
.B \-C
|
|
Equivalent to
|
|
.BR \-2 .
|
|
.TP
|
|
.B \-V
|
|
Print the version number of
|
|
.B grep
|
|
to standard error. This version number should
|
|
be included in all bug reports (see below).
|
|
.TP
|
|
.B \-b
|
|
Print the byte offset within the input file before
|
|
each line of output.
|
|
.TP
|
|
.B \-c
|
|
Suppress normal output; instead print a count of
|
|
matching lines for each input file.
|
|
With the
|
|
.B \-v
|
|
option (see below), count non-matching lines.
|
|
.TP
|
|
.BI \-e " pattern"
|
|
Use
|
|
.I pattern
|
|
as the pattern; useful to protect patterns beginning with
|
|
.BR \- .
|
|
.TP
|
|
.BI \-f " file"
|
|
Obtain the pattern from
|
|
.IR file .
|
|
.TP
|
|
.B \-h
|
|
Suppress the prefixing of filenames on output
|
|
when multiple files are searched.
|
|
.TP
|
|
.B \-i
|
|
Ignore case distinctions in both the
|
|
.I pattern
|
|
and the input files.
|
|
.TP
|
|
.B \-L
|
|
Suppress normal output; instead print the name
|
|
of each input file from which no output would
|
|
normally have been printed.
|
|
.TP
|
|
.B \-l
|
|
Suppress normal output; instead print
|
|
the name of each input file from which output
|
|
would normally have been printed.
|
|
.TP
|
|
.B \-n
|
|
Prefix each line of output with the line number
|
|
within its input file.
|
|
.TP
|
|
.B \-q
|
|
Quiet; suppress normal output.
|
|
.TP
|
|
.B \-s
|
|
Suppress error messages about nonexistent or unreadable files.
|
|
.TP
|
|
.B \-v
|
|
Invert the sense of matching, to select non-matching lines.
|
|
.TP
|
|
.B \-w
|
|
Select only those lines containing matches that form whole words.
|
|
The test is that the matching substring must either be at the
|
|
beginning of the line, or preceded by a non-word constituent
|
|
character. Similarly, it must be either at the end of the line
|
|
or followed by a non-word constituent character. Word-constituent
|
|
characters are letters, digits, and the underscore.
|
|
.TP
|
|
.B \-x
|
|
Select only those matches that exactly match the whole line.
|
|
.PD
|
|
.SH "REGULAR EXPRESSIONS"
|
|
.PP
|
|
A regular expression is a pattern that describes a set of strings.
|
|
Regular expressions are constructed analagously to arithmetic
|
|
expressions, by using various operators to combine smaller expressions.
|
|
.PP
|
|
.B Grep
|
|
understands two different versions of regular expression syntax:
|
|
``basic'' and ``extended.'' In
|
|
.RB "GNU\ " grep ,
|
|
there is no difference in available functionality using either syntax.
|
|
In other implementations, basic regular expressions are less powerful.
|
|
The following description applies to extended regular expressions;
|
|
differences for basic regular expressions are summarized afterwards.
|
|
.PP
|
|
The fundamental building blocks are the regular expressions that match
|
|
a single character. Most characters, including all letters and digits,
|
|
are regular expressions that match themselves. Any metacharacter with
|
|
special meaning may be quoted by preceding it with a backslash.
|
|
.PP
|
|
A list of characters enclosed by
|
|
.B [
|
|
and
|
|
.B ]
|
|
matches any single
|
|
character in that list; if the first character of the list
|
|
is the caret
|
|
.B ^
|
|
then it matches any character
|
|
.I not
|
|
in the list.
|
|
For example, the regular expression
|
|
.B [0123456789]
|
|
matches any single digit. A range of ASCII characters
|
|
may be specified by giving the first and last characters, separated
|
|
by a hyphen.
|
|
Finally, certain named classes of characters are predefined.
|
|
Their names are self explanatory, and they are
|
|
.BR [:alnum:] ,
|
|
.BR [:alpha:] ,
|
|
.BR [:cntrl:] ,
|
|
.BR [:digit:] ,
|
|
.BR [:graph:] ,
|
|
.BR [:lower:] ,
|
|
.BR [:print:] ,
|
|
.BR [:punct:] ,
|
|
.BR [:space:] ,
|
|
.BR [:upper:] ,
|
|
and
|
|
.BR [:xdigit:].
|
|
For example,
|
|
.B [[:alnum:]]
|
|
means
|
|
.BR [0-9A-Za-z] ,
|
|
except the latter form is dependent upon the ASCII character encoding,
|
|
whereas the former is portable.
|
|
(Note that the brackets in these class names are part of the symbolic
|
|
names, and must be included in addition to the brackets delimiting
|
|
the bracket list.) Most metacharacters lose their special meaning
|
|
inside lists. To include a literal
|
|
.B ]
|
|
place it first in the list. Similarly, to include a literal
|
|
.B ^
|
|
place it anywhere but first. Finally, to include a literal
|
|
.B \-
|
|
place it last.
|
|
.PP
|
|
The period
|
|
.B .
|
|
matches any single character.
|
|
The symbol
|
|
.B \ew
|
|
is a synonym for
|
|
.B [[:alnum:]]
|
|
and
|
|
.B \eW
|
|
is a synonym for
|
|
.BR [^[:alnum]] .
|
|
.PP
|
|
The caret
|
|
.B ^
|
|
and the dollar sign
|
|
.B $
|
|
are metacharacters that respectively match the empty string at the
|
|
beginning and end of a line.
|
|
The symbols
|
|
.B \e<
|
|
and
|
|
.B \e>
|
|
respectively match the empty string at the beginning and end of a word.
|
|
The symbol
|
|
.B \eb
|
|
matches the empty string at the edge of a word,
|
|
and
|
|
.B \eB
|
|
matches the empty string provided it's
|
|
.I not
|
|
at the edge of a word.
|
|
.PP
|
|
A regular expression matching a single character may be followed
|
|
by one of several repetition operators:
|
|
.PD 0
|
|
.TP
|
|
.B ?
|
|
The preceding item is optional and matched at most once.
|
|
.TP
|
|
.B *
|
|
The preceding item will be matched zero or more times.
|
|
.TP
|
|
.B +
|
|
The preceding item will be matched one or more times.
|
|
.TP
|
|
.BI { n }
|
|
The preceding item is matched exactly
|
|
.I n
|
|
times.
|
|
.TP
|
|
.BI { n ,}
|
|
The preceding item is matched
|
|
.I n
|
|
or more times.
|
|
.TP
|
|
.BI {, m }
|
|
The preceding item is optional and is matched at most
|
|
.I m
|
|
times.
|
|
.TP
|
|
.BI { n , m }
|
|
The preceding item is matched at least
|
|
.I n
|
|
times, but not more than
|
|
.I m
|
|
times.
|
|
.PD
|
|
.PP
|
|
Two regular expressions may be concatenated; the resulting
|
|
regular expression matches any string formed by concatenating
|
|
two substrings that respectively match the concatenated
|
|
subexpressions.
|
|
.PP
|
|
Two regular expressions may be joined by the infix operator
|
|
.BR | ;
|
|
the resulting regular expression matches any string matching
|
|
either subexpression.
|
|
.PP
|
|
Repetition takes precedence over concatenation, which in turn
|
|
takes precedence over alternation. A whole subexpression may be
|
|
enclosed in parentheses to override these precedence rules.
|
|
.PP
|
|
The backreference
|
|
.BI \e n\c
|
|
\&, where
|
|
.I n
|
|
is a single digit, matches the substring
|
|
previously matched by the
|
|
.IR n th
|
|
parenthesized subexpression of the regular expression.
|
|
.PP
|
|
In basic regular expressions the metacharacters
|
|
.BR ? ,
|
|
.BR + ,
|
|
.BR { ,
|
|
.BR | ,
|
|
.BR ( ,
|
|
and
|
|
.BR )
|
|
lose their special meaning; instead use the backslashed
|
|
versions
|
|
.BR \e? ,
|
|
.BR \e+ ,
|
|
.BR \e{ ,
|
|
.BR \e| ,
|
|
.BR \e( ,
|
|
and
|
|
.BR \e) .
|
|
.PP
|
|
In
|
|
.B egrep
|
|
the metacharacter
|
|
.B {
|
|
loses its special meaning; instead use
|
|
.BR \e{ .
|
|
.SH DIAGNOSTICS
|
|
.PP
|
|
Normally, exit status is 0 if matches were found,
|
|
and 1 if no matches were found. (The
|
|
.B \-v
|
|
option inverts the sense of the exit status.)
|
|
Exit status is 2 if there were syntax errors
|
|
in the pattern, inaccessible input files, or
|
|
other system errors.
|
|
.SH BUGS
|
|
.PP
|
|
Email bug reports to
|
|
.BR bug-gnu-utils@prep.ai.mit.edu .
|
|
Be sure to include the word ``grep'' somewhere in the ``Subject:'' field.
|
|
.PP
|
|
Large repetition counts in the
|
|
.BI { m , n }
|
|
construct may cause grep to use lots of memory.
|
|
In addition,
|
|
certain other obscure regular expressions require exponential time
|
|
and space, and may cause
|
|
.B grep
|
|
to run out of memory.
|
|
.PP
|
|
Backreferences are very slow, and may require exponential time.
|