How printf outputs the string type, and some key points of the c_str() function

Key points: printf can only output the built-in data of C language, but string is not built-in, it is just an extended class, and it is definitely wrong to output directly!

In fact, the method is very simple, just use the following function to output it:

string test = "测试代码段";

printf("%s",test.c_str());

Call the c_str() function to output, and use cout to output.

Here are a few notes about the c_str() function:

1. The c_str() function returns a pointer to a regular c string, the content of which is the same as the object of the string class itself, and the string object can be converted into the style of a string in c through the c_str() function of the string class;

2.

The c_str() function returns a pointer to a regular c string, the content of which is the same as this string.

　　This is for compatibility with the C language. There is no string type in the C language, so the string object must be converted into a string style in C through the member function c_str() of the string class object.

　　Note: Be sure to use the strcpy() function, etc. to manipulate the pointer returned by the method c_str()

　　For example: it is better not to:

　

char* p;

string test="test";

p = test.c_str(); //c最后指向的内容是废用，因为s对象被析构，其内容被处理

　It should be used like this:

char p[20];

string test="test";

strcpy(p,test.c_str());

In this way, c_str() returns a temporary pointer and cannot be manipulated.