How can my C/C++ application determine if the root user is executing the command?

Question

I am writing an application that requires root user privileges to execute. If executed by a non root user, it exits and terminates with a perror message such as:

<         


        

Answer 1

#include  // getuid
#include  // printf

int main()
{
    if (getuid()) printf("%s", "You are not root!\n");
    else printf("%s", "OK, you are root.\n");
    return 0;
}