C++11包含了几乎所有的Boost.Regex类和标志, 只要包含 <regex> 就是可以在std::下找到它们.
不过我还是喜欢/习惯于使用boost库(), 本文了演示多个例子.
引子
boost库提供了对正则表达式的支持(libboost_regex), 并且支持三种:
1. perl正则表达式(默认不忽略大小写)
2. posix基本正则表达式(默认不区分大小写)
3. posix扩展正则表达式(默认不区分大小写)
根据boost::regex::flag_type参数的不同, 选择不同的种类.
每次使用正则表达式, 都要先构造一个对象boost::regex, 之后根据需求进行匹配boost::regex_match(string, boost::regex)或者其他一些boost::regex_*函数.
即主要涉及两个类:
1. boost::regex //用于定义一个正则表达式对象
2. boost::smatch //用于保存匹配的结果(全串或者子串的结果)
具体可以参考一下文档下列的书籍:
1.《Beyond the C++ Standard Library: An Introduction to Boost》
2.《Boost C++ Application Development Cookbook》
3.《boost_1_56_pdf》regex部分
btw: 下面所有代码编译的时候记得链接boost_regex库(-lboost_regex).
正文
详细讲解
boost::regex
这就是代表正则表达式对象的类, 用来存储你写的正则表达式(如果你写的正则表达式不符合规范的话,可能会报错).
(但是又不会像posix c中对于正则表达式的支持, 需要先编译regcomp(), 之后才能进行匹配regexec())
创建了一个存储正则表达式的对象:(一般要加上const修饰)
1. boost::regex e(string_pattern, flag);
2. boost::regex e(string_pattern);
其中flag取不同的值, 可以设置不同的种类.
1. boost::regex::perl
2. boost::regex::perl | boost::regex::icase
3. boost::regex::extended
4. boost::regex::extended | boost::regex::icase
5. boost::regex::basic
6. boost::regex::basic | boost::regex::icase
还有一个取值, boost::regex::no_exception, 当string_pattern不符合正则表达式语法时,一般创建会失败,默认抛出异常.
但是如果你设置了上面的标志, 可以依赖”boost::regex.status()”进行判断.
boost::regex e(string_pattern, flag);
if(e.status){
//error happened
}
boost::regex_match
boost::regex e(string_pattern);
bool matched = boost::regex_match(target_string, e);
相对完整的demo:
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| #include <boost/regex.hpp>
#include <locale>
#include <iostream>
int main(void)
{
std::locale::global(std::locale("German"));
std::string s = "Boris Schaling";
boost::regex expr("\\w+\\s\\w+");
std::cout << boost::regex_match(s, expr) << std::endl;
return 0;
}
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boost::regex_research
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| #include <boost/regex.hpp>
#include <locale>
#include <iostream>
int main()
{
std::locale::global(std::locale("German"));
std::string s = "Boris Schaling";
boost::regex expr("(\\w+)\\s(\\w+)");
boost::smatch what;
if (boost::regex_search(s, what, expr)){
std::cout << what[0] << std::endl;
std::cout << what[1] << "-----" << what[2] << std::endl;
}
}
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boost::regex_replace
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| #include <boost/regex.hpp>
#include <locale>
#include <iostream>
int main()
{
std::locale::global(std::locale("German"));
std::string s = " Boris Schaling ";
boost::regex expr("\\s");
std::string fmt("_");
std::cout << boost::regex_replace(s, expr, fmt) << std::endl;
}
|
以及
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| #include <boost/regex.hpp>
#include <locale>
#include <iostream>
int main()
{
std::locale::global(std::locale("German"));
std::string s = "Boris Schaling";
boost::regex expr("(\\w+)\\s(\\w+)");
std::string fmt("\\2 \\1");
std::cout << boost::regex_replace(s, expr, fmt) << std::endl;
}
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| #include <boost/regex.hpp>
#include <locale>
#include <iostream>
int main(void)
{
std::locale::global(std::locale("German"));
std::string s = "Boris Schaling";
boost::regex expr("(\\w+)\\s(\\w+)");
std::string fmt("\\2 \\1");
std::cout << boost::regex_replace(s, expr, fmt,
boost::regex_constants::format_literal) << std::endl;
return 0;
}
|
规范代码
boost::regex_match
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| #include <boost/regex.hpp>
#include <iostream>
int main(void) {
std::cout
<< "Available regex syntaxes:\n"
<< "\t[0] Perl\n"
<< "\t[1] Perl case insensitive\n"
<< "\t[2] POSIX extended\n"
<< "\t[3] POSIX extended case insensitive\n"
<< "\t[4] POSIX basic\n"
<< "\t[5] POSIX basic case insensitive\n"
<< "Choose regex syntax: ";
boost::regex::flag_type flag;
switch (std::cin.get()) {
case '0': flag = boost::regex::perl;
break;
case '1': flag = boost::regex::perl|boost::regex::icase;
break;
case '2': flag = boost::regex::extended;
break;
case '3': flag = boost::regex::extended|boost::regex::icase;
break;
case '4': flag = boost::regex::basic;
break;
case '5': flag = boost::regex::basic|boost::regex::icase;
break;
default:
std::cout << "Inccorect number of regex syntax. Exiting... \n";
return -1;
}
flag |= boost::regex::no_except;
std::cin.ignore();
std::cin.clear();
std::string regex, str;
do {
std::cout << "Input regex: ";
if (!std::getline(std::cin, regex) || regex.empty()) {
return 0;
}
const boost::regex e(regex, flag);
if (e.status()) {
std::cout << "Incorrect regex pattern!\n";
continue;
}
std::cout << "String to match: ";
while (std::getline(std::cin, str) && !str.empty()) {
bool matched = boost::regex_match(str, e);
std::cout << (matched ? "MATCH\n" : "DOES NOT MATCH\n");
std::cout << "String to match: ";
}
std::cout << '\n';
std::cin.ignore();
std::cin.clear();
} while (1);
}
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boost::regex_replace
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| #include <boost/regex.hpp>
#include <iostream>
int main(void) {
std::cout
<< "Available regex syntaxes:\n"
<< "\t[0] Perl\n"
<< "\t[1] Perl case insensitive\n"
<< "\t[2] POSIX extended\n"
<< "\t[3] POSIX extended case insensitive\n"
<< "\t[4] POSIX basic\n"
<< "\t[5] POSIX basic case insensitive\n"
<< "Choose regex syntax: ";
boost::regex::flag_type flag;
switch (std::cin.get()) {
case '0': flag = boost::regex::perl;
break;
case '1': flag = boost::regex::perl|boost::regex::icase;
break;
case '2': flag = boost::regex::extended;
break;
case '3': flag = boost::regex::extended|boost::regex::icase;
break;
case '4': flag = boost::regex::basic;
break;
case '5': flag = boost::regex::basic|boost::regex::icase;
break;
default:
std::cout << "Inccorect number of regex syntax. Exiting... \n";
return -1;
}
flag |= boost::regex::no_except;
std::cin.ignore();
std::cin.clear();
std::string regex, str, replace_string;
do {
std::cout << "\nInput regex: ";
if (!std::getline(std::cin, regex)) {
return 0;
}
const boost::regex e(regex, flag);
if (e.status()) {
std::cout << "Incorrect regex pattern!\n";
continue;
}
std::cout << "String to match: ";
while (std::getline(std::cin, str) && !str.empty()) {
boost::smatch results;
bool matched = regex_search(str, results, e);
if (matched) {
std::cout << "MATCH: ";
std::copy(
results.begin() + 1,
results.end(),
std::ostream_iterator<std::string>( std::cout, ", ")
);
std::cout << "\nReplace pattern: ";
if (
std::getline(std::cin, replace_string)
&& !replace_string.empty())
{
std::cout << "RESULT: " << results.format(replace_string);
} else {
std::cin.ignore();
std::cin.clear();
}
} else {
std::cout << "DOES NOT MATCH";
}
std::cout << "\nString to match: ";
}
std::cout << '\n';
std::cin.ignore();
std::cin.clear();
} while (1);
return 0;
}
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尾巴
看到啦, 上面用起来还是挺舒服的.
当然如果想要兼容c和c++, 可以使用posix c提供的那一套, 如果只是C++, 建议用boost这一套.
并且c++11已经兼容了这一套, 直接引入<regex>头文件, 在std::下就可以用了.
c++11之前, 还是要引用boost库.
