使用regex.h的正则表达式 [英] Regular expressions using regex.h

问题描述

团队，
您能否建议一个站点，该站点实际上包含有关在Linux上的C语言中通过regex.h使用正则表达式的完整教程.

感谢您的回应.

问候，

Hi Team,
Can you please suggest a site which actually contains full tutorial about using regular expressions through regex.h in C on linux.

Appreciate your response.

Regards,

推荐答案

此处("C中的POSIX regex示例" [ ^ ])使用示例C中的POSIX正则表达式.这里是有关"10.3正则表达式匹配"的GNU文档 [ ^ ]正则表达式图书馆.使用Google，您可能会发现许多有关常规表达式的常规教程.

Here ( "Example of POSIX regex in C"[^] ) an example of using POSIX regular expressions in C. Here the GNU documentation about "10.3 Regular Expression Matching"[^] the regular expressions C library. With Google you may find many general tutorials on regular epressions.

不需要完整的教程，它们很容易使用.
请参见在线MAN页 [

No need for a full tutorial, they are simple to use.
See the online MAN page[^] for a full description

1. Compile an expression (this example is to match integer or decimal numbers)
2. Use that expression
3. Free the compiled expression when you are done with it

#include <sys/types.h>
#include <regex.h>
#include <stdio.h>

#define MAX_MATCHES 1 //The maximum number of matches allowed in a single string

void match(regex_t *pexp, char *sz) {
	regmatch_t matches[MAX_MATCHES]; //A list of the matches in the string (a list of 1)
	//Compare the string to the expression
	//regexec() returns 0 on match, otherwise REG_NOMATCH
	if (regexec(pexp, sz, MAX_MATCHES, matches, 0) == 0) {
		printf("\"%s\" matches characters %d - %d\n", sz, matches[0].rm_so, matches[0].rm_eo);
	} else {
		printf("\"%s\" does not match\n", sz);
	}
}

int main() {
	int rv;
	regex_t exp; //Our compiled expression
	//1. Compile our expression.
	//Our regex is "-?[0-9]+(\\.[0-9]+)?". I will explain this later.
	//REG_EXTENDED is so that we can use Extended regular expressions
	rv = regcomp(&exp, "-?[0-9]+(\\.[0-9]+)?", REG_EXTENDED);
	if (rv != 0) {
		printf("regcomp failed with %d\n", rv);
	}
	//2. Now run some tests on it
	match(&exp, "0");
	match(&exp, "0.");
	match(&exp, "0.0");
	match(&exp, "10.1");
	match(&exp, "-10.1");
	match(&exp, "a");
	match(&exp, "a.1");
	match(&exp, "0.a");
	match(&exp, "0.1a");
	match(&exp, "hello");
	//3. Free it
	regfree(&exp);
	return 0;
}

现在，对正则表达式进行基本说明.
原始的正则表达式非常基本.其中包括:

Now for a basic explanation of regular expressions.
The original regular expressions were pretty basic. They included:

One of         [AB]    one of A or B
Not one of     [^AB]   anything but A and B (new line may or may not be included, implementation or option specific)
Zero or more   A*      any number of A's including 0
Group          (A)     Used for grouping things like OR
Any character  .       Any single character (not including new line)

请参见 Wikipedia [ ^ ]以获得完整列表

然后是扩展的正则表达式，它添加了许多有用的功能:

See Wikipedia[^] for a full list

Then came extended regular expressions, which added many useful features:

Zero or one    A?      Either zero or 1 A (same as "A\{0,1\}" in basic regex)
Or             A|B     Either A or B
One or more    A+      One or more A's (same as "AA*" in basic regex)

请参见 Wikipedia [ ^ ]以获得完整列表

然后是预定义的字符列表，作为编写[ABC]的简写，请参见 Wikipedia [ ^ ].这些可以是特定于实现的，但是GNU可以支持Wikipedia列出的所有集合.

构造正则表达式的最简单方法是将其分解为最简单的部分，然后将它们组合在一起.
例如，我们需要一个表达式，该表达式将查找以A开头，以B结尾或以B开头并以A结尾的任何单词.

首先，将其分为2个部分
1. A. * B
2. B. * A

现在，将它们与OR
分组在一起 (A. * B)|(B. * A)
请注意，这与[AB].*[AB]不同，[AB].*[AB]也将匹配AA，AxA，BB，...

See Wikipedia[^] for a full list

Then there are predefined lists of characters, as a shorthand of writing [ABC], see Wikipedia[^] for a full list. These can be implementation specific, however the GNU one supports all sets listed at Wikipedia.

The easiest way to build a regular expression is to break it down into its simplest parts, and them combine them together.
For example we want an expression that will find any words starting with A and ending with B OR starting with B and ending with A.

First, break it into its 2 components
1. A.*B
2. B.*A

Now group them together with an OR
(A.*B)|(B.*A)
Note that this is different to [AB].*[AB], which will also match AA, AxA, BB, ...

尝试查看文档:
http://gnuwin32.sourceforge.net/packages/regex.htm [

Try looking at the documentation:
http://gnuwin32.sourceforge.net/packages/regex.htm[^]

Examples are included with the source, and the documentation is fairly decent - for this pupose the GnuWin32 download it''s equally applicable to linux/*nix.

Most likely this is already somewhere on your system :)

Best regards
Espen Harlinn

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