tcgetsid - get session ID of specified terminal

Syntax	#include <termios.h> pid_t tcgetsid(int fildes);
Description	tcgetsid() returns the process group ID of the session that is controlled by the terminal specified in fildes.
Return val.	Process group ID of the session associated with the specified terminal
		if successful.
	(pid_t)-1	otherwise. errno is set to indicate the error.
Errors	tcgetsid() will fail if:
	EACCES	No controlling terminal is assigned to the fildes argument.
	EBADF	The fildes argument is not a valid file descriptor.
	ENOTTY	The file fildes is not a terminal.
See also	termios.h.