在C ++中找到完全匹配的字符串

问题描述

这是我用来从txt文件检测一行中的字符串的代码:

Here is the code I used to detect the string in a line from a txt file:

int main()
{
    std::ifstream file( "C:\\log.txt" );

    std::string line;
    while(!file.eof())
    {
        while( std::getline( file, line ) )
        {
            int found = -1;
            if((found = line.find("GetSA"))>-1)
                std::cout<<"We found GetSA."<<std::endl;
            else if ((found = line.find("GetVol"))>-1)
                std::cout<<"We found GetVol."<<std::endl;
            else if ((found = line.find("GetSphereSAandVol"))>-1)
                std::cout<<"We found GetSphereSAandVol."<<std::endl;
            else
                std::cout<<"We found nothing!"<<std::endl;

        }
    }
    std::cin.get();
}

这是我的日志文件:

GetSA (3.000000)

GetVol (3.000000)

GetSphereSAandVol (3.000000)

GetVol (3.000000)

GetSphereSAandVol (3.000000)

GetSA (3.00000)

错误是，该程序将不会找到"GetSphereSAandVol"，因为它停止在"GetSA".显然，程序认为"GetSphereSAandVol"包含"GetSA"，因此它将执行:

The error is, the program will not go to find "GetSphereSAandVol", because it stops at "GetSA". Obviously, the program thinks "GetSphereSAandVol" contains "GetSA", so it will execute:

if(found = line.find("GetSA"))
    std::cout<<"We found GetSA."<<std::endl;

这并不是我想要的，因为我希望程序能够执行:

which is not exactly what I want, because I am expecting the program to execute:

else if (found = line.find("GetSphereSAandVol"))
    std::cout<<"We found GetSphereSAandVol."<<std::endl;

因此，无论如何我都可以避免这种情况?得到我真正想要的?非常感谢.

So, anyway I can avoid this? to get what I really want? Thanks a lot.

推荐答案

您误解了find的工作方式.阅读文档.

You misunderstand how find works. Read the documentation.

条件句应该这样:

if ((found = line.find("xyz")) != line.npos) { /* found "xyz" */ }

---

我会这样编写整个程序:

---

I would write your entire program like this:

int main(int argc, char * argv[])
{
    if (argc != 2) { std::cout << "Bad invocation\n"; return 0; }

    std::ifstream infile(argv[1]);

    if (!infile) { std::cout << "Bad filename '" << argv[1] << "'\n"; return 0; }

    for (std::string line; std::getline(infile, line); )
    {
        int pos;

        if ((pos = line.find("abc")) != line.npos)
        {
            std::cout << "Found line 'abc'\n";
            continue;
        }

        if ((pos = line.find("xyz")) != line.npos)
        {
            std::cout << "Found line 'xyz'\n";
            continue;
        }

        // ...

        std::cout << "Line '" << line << "' did not match anything.\n";
    }
}

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