c++11 正则表达式基本使用

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
",(int)result.size());
        for (int i = 0; i < result.size(); ++i) {
            printf("result[%d]:%s
",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]:	%s
",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
",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.
内容基本来自于: 这个作者