Find controlling terminal with ttyname

You can identify the path the the controlling terminal device path for your current process in C with the ttyname() system call. This controlling terminal can be a virtual console (/dev/ttyn) or a pseudo-terminal (/dev/pts/n).
The ttyname system call takes the following format.
char *ttyname(int fd);
The stdin, stdout, stderr file descriptors unless redirected are by default [...]