什么是使用c_str函数在C ++中 [英] What is use of c_str function In c++

问题描述

我刚开始读C ++，发现C ++具有它C没有字符串操作功能丰富。我读这些功能，并在 c_str（）键，从我的理解是 c_str 转换可能是一个字符串来空终止，也可能不是一个空结尾的字符串。是真的吗？

I have just started reading C++ and found c++ having rich functions for string manipulation which C does not have. I am reading these function and came across c_str() and from what I understand is c_str convert a string which may be null terminated or may not be to a null terminated string .Is it true?

任何人都可以建议我一些示例，这样我可以了解采用的 c_str 函数??

Can anyone suggest me some example so that i can understand the use of c_str function??

推荐答案

c_str 返回为const char * 的指向空结尾的字符串（如C风格的字符串）。当你想传递一个的std ::字符串来一个函数，愿与C风格的字符串工作的内容¹是有用的。

c_str returns a const char* that points to a null-terminated string (i.e. a C-style string). It is useful when you want to pass the "contents"¹ of an std::string to a function that expects to work with a C-style string.

例如，考虑这个code：

For example, consider this code:

std::string str("Hello world!");
int pos1 = str.find_first_of('w');

int pos2 = strchr(str.c_str(), 'w') - str.c_str();

if (pos1 == pos2) {
    printf("Both ways give the same result.\n");
}

看到它在行动

See it in action.

注：

¹这是不完全正确，因为的std ::字符串（不像C字符串），可以包含 \\ 0 字符。如果确实如此，接收c_str 的返回值code（）会误以为该字符串比它短真的是，因为它会间preT \\ 0 作为字符串的结尾。

¹ This is not entirely true because an std::string (unlike a C string) can contain the \0 character. If it does, the code that receives the return value of c_str() will be fooled into thinking that the string is shorter than it really is, since it will interpret \0 as the end of the string.

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