599 lines
14 KiB
Groff
599 lines
14 KiB
Groff
.\" grep man page
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.\" $FreeBSD$
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.if !\n(.g \{\
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. if !\w|\*(lq| \{\
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. ds lq ``
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. if \w'\(lq' .ds lq "\(lq
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. \}
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. if !\w|\*(rq| \{\
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. ds rq ''
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. if \w'\(rq' .ds rq "\(rq
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. \}
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.\}
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.de Id
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.ds Dt \\$4
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..
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.Id $Id: grep.1,v 1.7 1999/10/12 20:41:01 alainm Exp $
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.TH GREP 1 \*(Dt "GNU Project"
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.SH NAME
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grep, egrep, fgrep, zgrep \- print lines matching a pattern
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.SH SYNOPSIS
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.B grep
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.RB [ \- [ ABC ]
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.IR NUM ]
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.RB [ \-EFGHLUVZabchilnqrsuvwxyz ]
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.RB [ \-e
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.I PATTERN
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.B \-f
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.IR FILE ]
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.RB [ \-d
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.IR ACTION ]
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.RB [ \-\^\-directories=\fIACTION\fP ]
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.RB [ \-\^\-extended-regexp ]
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.RB [ \-\^\-fixed-strings ]
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.RB [ \-\^\-basic-regexp ]
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.RB [ \-\^\-regexp=\fIPATTERN\fP ]
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.RB [ \-\^\-file=\fIFILE\fP ]
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.RB [ \-\^\-ignore-case ]
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.RB [ \-\^\-word-regexp ]
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.RB [ \-\^\-line-regexp ]
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.RB [ \-\^\-line-regexp ]
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.RB [ \-\^\-no-messages ]
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.RB [ \-\^\-invert-match ]
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.RB [ \-\^\-version ]
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.RB [ \-\^\-help ]
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.RB [ \-\^\-byte-offset ]
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.RB [ \-\^\-line-number ]
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.RB [ \-\^\-with-filename ]
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.RB [ \-\^\-no-filename ]
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.RB [ \-\^\-quiet ]
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.RB [ \-\^\-silent ]
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.RB [ \-\^\-text ]
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.RB [ \-\^\-files-without-match ]
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.RB [ \-\^\-files-with-matches ]
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.RB [ \-\^\-count ]
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.RB [ \-\^\-before-context=\fINUM\fP ]
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.RB [ \-\^\-after-context=\fINUM\fP ]
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.RB [ \-\^\-context [ =\fINUM\fP ]]
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.RB [ \-\^\-binary ]
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.RB [ \-\^\-unix-byte-offsets ]
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.RB [ \-\^\-mmap ]
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.RB [ \-\^\-null ]
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.RB [ \-\^\-recursive ]
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.RB [ \-\^\-decompress ]
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.RI [ file .\|.\|.]
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.SH DESCRIPTION
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.PP
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.B grep
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searches the named input
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.I files
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(or standard input if no files are named, or
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the file name
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.B \-
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is given)
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for lines containing a match to the given
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.IR pattern .
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By default,
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.B grep
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prints the matching lines.
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.PP
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There are three major variants of
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.BR grep ,
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controlled by the following options.
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.PD 0
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.TP
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.BR \-G ", " \-\^\-basic-regexp
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Interpret
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.I pattern
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as a basic regular expression (see below). This is the default.
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.TP
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.BR \-E ", " \-\^\-extended-regexp
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Interpret
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.I pattern
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as an extended regular expression (see below).
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.TP
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.BR \-F ", " \-\^\-fixed-strings
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Interpret
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.I pattern
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as a list of fixed strings, separated by newlines,
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any of which is to be matched.
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.PP
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In addition, two variant programs
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.B egrep
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and
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.B fgrep
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are available.
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.B egrep
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is the same as
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.BR "grep\ \-E" .
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.B fgrep
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is the same as
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.BR "grep\ \-F" .
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.B zgrep
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is the same as
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.BR "grep\ \-Z" .
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.PD
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.PP
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All variants of
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.B grep
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understand the following options:
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.PD 0
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.TP
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.BI \-A " NUM" "\fR,\fP \-\^\-after-context=" NUM
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Print
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.I NUM
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lines of trailing context after matching lines.
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.TP
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.BI \-B " NUM" "\fR,\fP \-\^\-before-context=" NUM
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Print
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.I NUM
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lines of leading context before matching lines.
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.TP
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.BI \-C " \fR[\fPNUM\fR]\fP" "\fR,\fP \-\^\-context\fR[\fP=" NUM\fR]\fP
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Print
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.I NUM
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lines (default 2) of output context.
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.TP
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.BI \- NUM
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Same as
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.BI \-\^\-context= NUM
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lines of leading and trailing context. However,
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.B grep
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will never print any given line more than once.
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.TP
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.BR \-V ", " \-\^\-version
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Print the version number of
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.B grep
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to standard error. This version number should
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be included in all bug reports (see below).
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.TP
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.BR \-b ", " \-\^\-byte-offset
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Print the byte offset within the input file before
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each line of output.
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.TP
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.BR \-c ", " \-\^\-count
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Suppress normal output; instead print a count of
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matching lines for each input file.
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With the
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.BR \-v ", " \-\^\-invert-match
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option (see below), count non-matching lines.
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.TP
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.BI \-d " ACTION" "\fR,\fP \-\^\-directories=" ACTION
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If an input file is a directory, use
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.I ACTION
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to process it. By default,
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.I ACTION
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is
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.BR read ,
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which means that directories are read just as if they were ordinary files.
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If
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.I ACTION
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is
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.BR skip ,
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directories are silently skipped.
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If
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.I ACTION
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is
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.BR recurse ,
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.B
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grep reads all files under each directory, recursively;
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this is equivalent to the
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.B \-r
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option.
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.TP
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.BI \-e " PATTERN" "\fR,\fP \-\^\-regexp=" PATTERN
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Use
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.I PATTERN
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as the pattern; useful to protect patterns beginning with
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.BR \- .
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.TP
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.BI \-f " FILE" "\fR,\fP \-\^\-file=" FILE
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Obtain patterns from
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.IR FILE ,
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one per line.
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The empty file contains zero patterns, and therfore matches nothing.
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.TP
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.BR \-H ", " \-\^\-with-filename
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Print the filename for each match.
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.TP
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.BR \-h ", " \-\^\-no-filename
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Suppress the prefixing of filenames on output
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when multiple files are searched.
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.TP
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.BR \-i ", " \-\^\-ignore-case
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Ignore case distinctions in both the
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.I pattern
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and the input files.
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.TP
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.BR \-L ", " \-\^\-files-without-match
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Suppress normal output; instead print the name
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of each input file from which no output would
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normally have been printed. The scanning will stop
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on the first match.
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.TP
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.BR \-l ", " \-\^\-files-with-matches
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Suppress normal output; instead print
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the name of each input file from which output
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would normally have been printed. The scanning will
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stop on the first match.
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.TP
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.BR \-n ", " \-\^\-line-number
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Prefix each line of output with the line number
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within its input file.
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.TP
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.BR \-q ", " \-\^\-quiet ", " \-\^\-silent
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Quiet; suppress normal output. The scanning will stop
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on the first match.
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Also see the
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.B \-s
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or
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.B \-\^\-no-messages
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option below.
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.TP
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.BR \-r ", " \-\^\-recursive
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Read all files under each directory, recursively;
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this is equivalent to the
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.B "\-d recurse"
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option.
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.TP
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.BR \-s ", " \-\^\-no-messages
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Suppress error messages about nonexistent or unreadable files.
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Portability note: unlike \s-1GNU\s0
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.BR grep ,
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traditional
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.B grep
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did not conform to \s-1POSIX.2\s0, because traditional
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.B grep
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lacked a
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.B \-q
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option and its
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.B \-s
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option behaved like \s-1GNU\s0
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.BR grep 's
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.B \-q
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option.
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Shell scripts intended to be portable to traditional
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.B grep
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should avoid both
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.B \-q
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and
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.B \-s
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and should redirect output to /dev/null instead.
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.TP
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.BR \-a ", " \-\^\-text
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Do not suppress output lines that contain binary data.
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Normally, if the first few bytes of a file indicate that
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the file contains binary data,
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.B grep
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outputs only a message saying that the file matches the pattern.
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This option causes
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.B grep
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to act as if the file is a text file,
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even if it would otherwise be treated as binary.
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.TP
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.BR \-v ", " \-\^\-invert-match
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Invert the sense of matching, to select non-matching lines.
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.TP
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|
.BR \-w ", " \-\^\-word-regexp
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Select only those lines containing matches that form whole words.
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The test is that the matching substring must either be at the
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beginning of the line, or preceded by a non-word constituent
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character. Similarly, it must be either at the end of the line
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or followed by a non-word constituent character. Word-constituent
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characters are letters, digits, and the underscore.
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.TP
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.BR \-x ", " \-\^\-line-regexp
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Select only those matches that exactly match the whole line.
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.TP
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.B \-y
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Obsolete synonym for
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.BR \-i .
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.TP
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.BR \-U ", " \-\^\-binary
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Treat the file(s) as binary. By default, under MS-DOS and MS-Windows,
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.BR grep
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guesses the file type by looking at the contents of the first 32KB
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read from the file. If
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.BR grep
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decides the file is a text file, it strips the CR characters from the
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original file contents (to make regular expressions with
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.B ^
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and
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.B $
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work correctly). Specifying
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.B \-U
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overrules this guesswork, causing all files to be read and passed to the
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matching mechanism verbatim; if the file is a text file with CR/LF
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pairs at the end of each line, this will cause some regular
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expressions to fail.
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This option has no effect on platforms other than MS-DOS and
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MS-Windows.
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.TP
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.BR \-u ", " \-\^\-unix-byte-offsets
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Report Unix-style byte offsets. This switch causes
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.B grep
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to report byte offsets as if the file were Unix-style text file, i.e. with
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CR characters stripped off. This will produce results identical to running
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.B grep
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on a Unix machine. This option has no effect unless
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.B \-b
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option is also used;
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it has no effect on platforms other than MS-DOS and MS-Windows.
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.TP
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.B \-\^\-mmap
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If possible, use the
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.BR mmap (2)
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system call to read input, instead of
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the default
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.BR read (2)
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system call. In some situations,
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.B -\^-mmap
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yields better performance. However,
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.B -\^-mmap
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can cause undefined behavior (including core dumps)
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if an input file shrinks while
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.B grep
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is operating, or if an I/O error occurs.
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.TP
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.BR \-Z ", " \-\^\-null
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Output a zero byte (the \s-1ASCII\s0
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.B NUL
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character) instead of the character that normally follows a file name.
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For example,
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.B "grep \-lZ"
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outputs a zero byte after each file name instead of the usual newline.
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This option makes the output unambiguous, even in the presence of file
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names containing unusual characters like newlines. This option can be
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used with commands like
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.BR "find \-print0" ,
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.BR "perl \-0" ,
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.BR "sort \-z" ,
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and
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.B "xargs \-0"
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to process arbitrary file names,
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even those that contain newline characters.
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.PD
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.LP
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Following option is only available if compiled with zlib(3) library:
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.PD 0
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.TP
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.B \-Z, --decompress
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Decompress the input data before searching.
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.PD
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.SH "REGULAR EXPRESSIONS"
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.PP
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A regular expression is a pattern that describes a set of strings.
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Regular expressions are constructed analogously to arithmetic
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expressions, by using various operators to combine smaller expressions.
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.PP
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.B grep
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understands two different versions of regular expression syntax:
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\*(lqbasic\*(rq and \*(lqextended.\*(rq In
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.RB "\s-1GNU\s0\ " grep ,
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there is no difference in available functionality using either syntax.
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In other implementations, basic regular expressions are less powerful.
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The following description applies to extended regular expressions;
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differences for basic regular expressions are summarized afterwards.
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.PP
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The fundamental building blocks are the regular expressions that match
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a single character. Most characters, including all letters and digits,
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are regular expressions that match themselves. Any metacharacter with
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special meaning may be quoted by preceding it with a backslash.
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.PP
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A list of characters enclosed by
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.B [
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and
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.B ]
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matches any single
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character in that list; if the first character of the list
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is the caret
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.B ^
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then it matches any character
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.I not
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in the list.
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For example, the regular expression
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.B [0123456789]
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matches any single digit. A range of ASCII characters
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may be specified by giving the first and last characters, separated
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by a hyphen.
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Finally, certain named classes of characters are predefined.
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Their names are self explanatory, and they are
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.BR [:alnum:] ,
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.BR [:alpha:] ,
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.BR [:cntrl:] ,
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.BR [:digit:] ,
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.BR [:graph:] ,
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.BR [:lower:] ,
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.BR [:print:] ,
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.BR [:punct:] ,
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.BR [:space:] ,
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.BR [:upper:] ,
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and
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.BR [:xdigit:].
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For example,
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.B [[:alnum:]]
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means
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.BR [0-9A-Za-z] ,
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except the latter form is dependent upon the ASCII character encoding,
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whereas the former is portable.
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(Note that the brackets in these class names are part of the symbolic
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names, and must be included in addition to the brackets delimiting
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the bracket list.) Most metacharacters lose their special meaning
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inside lists. To include a literal
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.B ]
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place it first in the list. Similarly, to include a literal
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.B ^
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place it anywhere but first. Finally, to include a literal
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.B \-
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place it last.
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.PP
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The period
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.B .
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matches any single character.
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|
The symbol
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.B \ew
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is a synonym for
|
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.B [[:alnum:]]
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and
|
|
.B \eW
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|
is a synonym for
|
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.BR [^[:alnum]] .
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.PP
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|
The caret
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|
.B ^
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|
and the dollar sign
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.B $
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|
are metacharacters that respectively match the empty string at the
|
|
beginning and end of a line.
|
|
The symbols
|
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.B \e<
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|
and
|
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.B \e>
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|
respectively match the empty string at the beginning and end of a word.
|
|
The symbol
|
|
.B \eb
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|
matches the empty string at the edge of a word,
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|
and
|
|
.B \eB
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|
matches the empty string provided it's
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.I not
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|
at the edge of a word.
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.PP
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|
A regular expression may be followed by one of several repetition operators:
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.PD 0
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|
.TP
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.B ?
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|
The preceding item is optional and matched at most once.
|
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.TP
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|
.B *
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|
The preceding item will be matched zero or more times.
|
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.TP
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|
.B +
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|
The preceding item will be matched one or more times.
|
|
.TP
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|
.BI { n }
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|
The preceding item is matched exactly
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.I n
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|
times.
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.TP
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|
.BI { n ,}
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|
The preceding item is matched
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.I n
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|
or more times.
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|
.TP
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|
.BI { n , m }
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|
The preceding item is matched at least
|
|
.I n
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|
times, but not more than
|
|
.I m
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|
times.
|
|
.PD
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|
.PP
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|
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
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|
Two regular expressions may be joined by the infix operator
|
|
.BR | ;
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|
the resulting regular expression matches any string matching
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|
either subexpression.
|
|
.PP
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|
Repetition takes precedence over concatenation, which in turn
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|
takes precedence over alternation. A whole subexpression may be
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|
enclosed in parentheses to override these precedence rules.
|
|
.PP
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|
The backreference
|
|
.BI \e n\c
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|
\&, where
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.I n
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|
is a single digit, matches the substring
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previously matched by the
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.IR n th
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|
parenthesized subexpression of the regular expression.
|
|
.PP
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|
In basic regular expressions the metacharacters
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.BR ? ,
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.BR + ,
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.BR { ,
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|
.BR | ,
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|
.BR ( ,
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|
and
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|
.BR )
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|
lose their special meaning; instead use the backslashed
|
|
versions
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|
.BR \e? ,
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.BR \e+ ,
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.BR \e{ ,
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|
.BR \e| ,
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.BR \e( ,
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and
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.BR \e) .
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.PP
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|
Traditional
|
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.B egrep
|
|
did not support the
|
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.B {
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metacharacter, and some
|
|
.B egrep
|
|
implementations support
|
|
.B \e{
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|
instead, so portable scripts should avoid
|
|
.B {
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|
in
|
|
.B egrep
|
|
patterns and should use
|
|
.B [{]
|
|
to match a literal
|
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.BR { .
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.PP
|
|
\s-1GNU\s0
|
|
.B egrep
|
|
attempts to support traditional usage by assuming that
|
|
.B {
|
|
is not special if it would be the start of an invalid interval
|
|
specification. For example, the shell command
|
|
.B "egrep '{1'"
|
|
searches for the two-character string
|
|
.B {1
|
|
instead of reporting a syntax error in the regular expression.
|
|
\s-1POSIX.2\s0 allows this behavior as an extension, but portable scripts
|
|
should avoid it.
|
|
.SH ENVIRONMENT
|
|
The environment variable
|
|
.B GREP_OPTIONS
|
|
can hold a set of default
|
|
options for
|
|
.I grep.
|
|
These options are interpreted first and can be overwritten by explicit command
|
|
line parameters.
|
|
.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@gnu.org .
|
|
Be sure to include the word \*(lqgrep\*(rq somewhere in the
|
|
\*(lqSubject:\*(rq 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.
|
|
.\" Work around problems with some troff -man implementations.
|
|
.br
|