为什么在使用 isdigit function 时出现分段错误？

Question

I run into segmentation fault while implementing the following program. Though, the code seems to work partially when I change the variable argv into char *argv, and make subsequent pointers.

int main(int argc, string argv[] ){

    if(argc == 1) {
        printf("Error");
    }
    else if (argc ==2 )
    {
        if(isdigit(argv[1]))
        {
        int key = atoi (argv[1]);
        printf("Success");

        }
    }
    else  {

       printf("Error");

    }

}

Answer 1

isdigit() expects a character argument, but you're passing a pointer. You probably want to loop over all the characters in argv[1] , and make sure they're all digits before calling atoi() .