Grep Version 2.0
SYNOPOSIS
grep [-[[AB] ]<num>] [-[CEFGLSVbchilnqsvwx?]] [-[ef]] <expr> [<files...>]
DESCRIPTION
Grep searches the named input files (or standard input if no files are named, or
the file name - is given) for lines containing a match to the given pattern.
By default, grep prints the matching lines. There are three major variants of
grep, controlled by the following options.
-G Interpret pattern as a basic regular expression (see below). This is
the default.
-E Interpret pattern as an extended regular expression (see below).
-F Interpret pattern as a list of fixed strings, separated by newlines,
any of which is to be matched.
In addition, two variant programs egrep and fgrep are available. Egrep is
similiar (but not identical) to "grep -E", and is compatible with the
historical Unix egrep. Fgrep is the same as "grep -F".
All variants of grep understand the following options:
-num Matches will be printed with num lines of leading and trailing
context. However, grep will never print any given line more than once.
-A "num" Print num lines of trailing context after matching lines.
-B "num" Print num lines of leading context before matching lines.
-C Equivalent to -2.
-S Search subdirectories.
-V Print the version number of grep to standard error. This version
number should be included in all bug reports (see below).
-b Print the byte offset within the input file before each line of output.
-c Suppress normal output; instead print a count of matching lines for
each input file. With the -v option (see below), count non-matching
lines.
-e "pattern" Use pattern as the pattern; useful to protect patterns
beginning with -.
-f "file" Obtain the pattern from file.
-h Suppress the prefixing of filenames on output when multiple files are
searched.
-i Ignore case distinctions in both the pattern and the input files.
-L Suppress normal output; instead print the name of each input file from
which no output would normally have been printed.
-l Suppress normal output; instead print the name of each input file from
which output would normally have been printed.
-n Prefix each line of output with the line number within its input file.
-q Quiet; suppress normal output.
-s Suppress error messages about nonexistent or unreadable files.
-v Invert the sense of matching, to select non-matching lines.
-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.
-x Select only those matches that exactly match the whole line.
-? Displays help summary
REGULAR EXPRESSIONS
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.
Grep understands two different versions of regular expression syntax:
``basic'' and ``extended.'' In "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.
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.
A list of characters enclosed by [ and ] matches any single character in
that list; if the first character of the list is the caret ^ then it
matches any character not in the list.
For example, the regular expression [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
[:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:],
[:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
For example, [[:alnum:]] means [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 ] place it first in the list.
Similarly, to include a literal ^ place it anywhere but first. Finally,
to include a literal - place it last.
The period . matches any single character. The symbol \w is a synonym for
[[:alnum:]] and \W is a synonym for [^[:alnum]].
The caret ^ and the dollar sign $ are metacharacters that respectively
match the empty string at the beginning and end of a line. The symbols
\< and \> respectively match the empty string at the beginning and end
of a word. The symbol \b matches the empty string at the edge of a word,
and \B matches the empty string provided it's not at the edge of a word.
A regular expression matching a single character may be followed
by one of several repetition operators:
? The preceding item is optional and matched at most once.
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{ n } The preceding item is matched exactly n times.
{ n,} The preceding item is matched n or more times.
{,m } The preceding item is optional and is matched at most m times.
{ n,m} The preceding item is matched at least n times, but not more than
m times.
Two regular expressions may be concatenated; the resulting regular
expression matches any string formed by concatenating two substrings that
respectively match the concatenated subexpressions.
Two regular expressions may be joined by the infix operator |; the
resulting regular expression matches any string matching either
subexpression.
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.
The backreference \n, where n is a single digit, matches the substring
previously matched by the nth parenthesized subexpression of the regular
expression.
In basic regular expressions the metacharacters ?, +, {, |, (, and ) lose
their special meaning; instead use the backslashed versions \?, \+, \{,
\|, \(, and \).
In egrep the metacharacter { loses its special meaning; instead use \{ .
DIAGNOSTICS
Normally, exit status is 0 if matches were found, and 1 if no matches were
found. (The -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.
BUGS
Email bug reports to bug-gnu-utils@prep.ai.mit.edu . Be sure to include
the word ``grep'' somewhere in the ``Subject:'' field.
Large repetition counts in the { 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 grep to run out of
memory.
Backreferences are very slow, and may require exponential time.
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grep程序的源代码
共39个文件
c:8个
h:7个
man:2个
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2008-11-22
01:07:46
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grep程序的源代码,可以直接用VC打开编译,算法值得学习
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grep_win.zip (39个子文件)
grep_win
COPYING 18KB
grep.dsp 4KB
regex.h 18KB
kwset.h 2KB
kwset.c 21KB
getopt.h 4KB
grep.h 1KB
Makefile.watcom 1KB
tests
spencer.tests 2KB
scriptgen.awk 280B
khadafy.regexp 66B
check.sh 530B
khadafy.lines 728B
dfa.c 62KB
INSTALL 5KB
obstack.h 18KB
PROJECTS 684B
ChangeLog 88B
Debug
getpagesize.h 741B
grep.c 25KB
grep.plg 242B
obstack.c 14KB
grep.txt 8KB
AUTHORS 1KB
search.c 11KB
MANIFEST 1KB
grep.man 8KB
dfa.h 14KB
ggrep.man 8KB
README 1KB
grep.ncb 89KB
grep.opt 49KB
NEWS 2KB
grep.dsw 533B
getopt.c 20KB
grep.exe 101KB
alloca.c 13KB
README.W32 3KB
regex.c 159KB
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- ayaasuka2013-11-03How it could be. It is not a c++.
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