c++11 正则表达式基本使用

2022-11-24 17:30:19

c++ 11 正则表达式

常用的方法 regex_match regex_search regex_replace 等.

regex_match 要求正则表达式必须与模式串完全匹配,例如:

string str = "o ";

regex pattern("o\\s");

bool matched = regex_match(str,pattern);

if (matched) {

    cout << "matched.." << endl;

}else{

    cout << "not matched." << endl;

}

上面就可以匹配.如果修改一下下:

string str = "o 1";

regex pattern("o\\s");

bool matched = regex_match(str,pattern);

if (matched) {

    cout << "matched.." << endl;

}else{

    cout << "not matched." << endl;

}

就是 not matched. 了

regex_match 包含子模式的匹配,并且显示匹配结果,主要使用了

match_results<string::const_iterator> result

存储匹配后的结果.

    string str = "1:2:33:344";

    regex pattern("(\\d{1,3}):(\\d{1,3}):(\\d{1,3}):(\\d{1,3})");

    match_results<string::const_iterator> result;

    bool matched = regex_match(str,result,pattern);

    if (matched) {

        cout << "matched.." << endl;

        printf("result.size = %d\n",(int)result.size());

        for (int i = 0; i < result.size(); ++i) {

            printf("result[%d]:%s\n",i,result[i].str().c_str());

        }

    }else{

        cout << "not matched." << endl;

    }

输出:

matched..

result.size = 5

result[0]:1:2:33:344

result[1]:1

result[2]:2

result[3]:33

result[4]:344

主意打印的结果result[0]

regex_search 只要求存在匹配项就可以.

string str = "o 1";

regex pattern("\\w\\s");

bool matched = regex_search(str,pattern);

if (matched) {

    cout << "matched.." << endl;

}else{

    cout << "not matched." << endl;

}

输出: matched..

如果只想输出第一个匹配项,使用 smatch 存储结果

string str = "o 1s;23235;t;dsf;sd 66 ";

regex pattern(";");

smatch result;

bool matched = regex_search(str,result,pattern);

if (matched) {

    cout << "matched.." << endl;

    cout <<  "result.size:" << result.size() << endl;

    for (int i = 0; i < result.size(); ++i) {

        printf("result[%d]:\t%s\n",i,result[i].str().c_str());

    }

}else{

    cout << "not matched." << endl;

}

输出结果为:

matched..

result.size:1

result[0]: ;

如果想输出所有的匹配结果,则需要使用 sregex_token_iterator

string str = "o 1s 23235 t ds f sd 66 ";

regex pattern("\\w\\s");

sregex_token_iterator end;

sregex_token_iterator start(str.begin(),str.end(),pattern);

while (start != end) {

    cout << (*start) << endl;

    ++start;

}

输出为:

o

s

5

t

s

f

d

6

regex_replace 方法替换掉匹配上的

string str = "o 1s 23235 t ds f sd 66 ";

regex pattern("\\w\\s");

bool matched = regex_search(str,pattern);

if (matched) {

    cout << "matched ." << endl;

    auto newStr = regex_replace(str,pattern,"---");

    printf("newStr : %s\n",newStr.c_str());

}else{

    cout << "not matched ." << endl;

}

输出结果为:

matched .

newStr : ---1---2323------d------s---6---

上面就是c++11 正则表达式的基本使用.

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