通过命令行参数传递文件名与使用字符串文字in-code

Question

The following bit of code seems to interpret the slash in the passed filename differently, depending on whether it was passed as a command line argument, or hardcoded by means of a literal. If the image filename C:\\kimba.jpg is passed in as a command line argument, it works fine:

int main( int argc, char** argv ) 
{
    IplImage* img = cvLoadImage(argv[1]);
    //IplImage* img = cvLoadImage("C:\kimba.jpg", 1);

    // ...

    return 0;
}

If, on the other hand, I uncomment the second line and comment the first, the same filename causes an exception in that line. I do not know how cvLoadImage() is implemented, but it seems (according to the debugger) that in both cases the same content is being passed to the function. So why does the hardcoded filename cause an exception and not the command-line argument?

Answer 1

你需要用反斜杠来逃避反斜杠：

IplImage* img = cvLoadImage("C:\\kimba.jpg", 1);

Answer 2

the '\\' character is the escape character in C++. To get a '\\' character literal, you need to escape it (note the double '\\'):

IplImage* img = cvLoadImage("C:\\kimba.jpg", 1);

HTH.

Answer 3

使用"C:\\\\kimba.jpg" - \\用于转义特殊字符，例如\\n

Answer 4

Backslash in string literals is an escape character, while in command line argument it is interpreted as-is. So in the second case the file is not found and you get an exception.