C ++比较C字符串的麻烦 [英] C++ comparing c string troubles

问题描述

我编写了下面的代码，该代码将不起作用，但是当我更改它时，第二个代码段将起作用。

I have written the following code which will does not work but the second snippet will when I change it.

int main( int argc, char *argv[] )
{
  if( argv[ 1 ] == "-i" )   //This is what does not work
     //Do Something
}

但是如果我编写这样的代码，这将起作用。

But if I write the code like so this will work.

int main( int argc, char *argv[] )
{
  string opti = "-i";

  if( argv[ 1 ] == opti )   //This is what does work
     //Do Something
}

是因为字符串类具有==作为重载成员，因此可以执行此操作？

Is it because the string class has == as an overloaded member and hence can perform this action?

预先感谢。

推荐答案

是因为字符串类具有==作为重载成员，因此可以执行此操作？

Is it because the string class has == as an overloaded member and hence can perform this action?

您是正确的。类型 char * 的常规值没有重载运算符。要比较C字符串，

You are correct. Regular values of type char * do not have overloaded operators. To compare C strings,

if (strcmp(argv[1], "-i") == 0) {
    ...
}

通过比较字符串的方式（用 == 直接），您正在比较指针的值。因为-i 是一个编译时间常数，而 argv [1] 是一个编译时间常数，所以它们永远不会相等

By comparing the strings the way you did (with == directly), you are comparing the values of the pointers. Since "-i" is a compile time constant and argv[1] is something else, they will never be equal.

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