Open system call in linux

Question

I noticed that there are two prototypes for open system call in linux,

int open(const char *pathname, int flags);
int open(const char *pathname, int flags, mode_t mode);

I would like to know how the C compiler can differentiate b/w both calls, given C compiler doesn't support function overloading?

Answer 1

Hello Shivam,
I agree with your statement that C language does not support function overloading. However, C language supports function with variable number of arguments. In this case, open system call has following syntax.
int open(const char *path, int oflag, .../*,mode_t mode */);
It is why it can be called with different set of parameters. First two parameters will be fixed based on position and other parameters can be passed at third position and so on.

Comments

Thanks