int openty(int ptys[2]);
This syscalls creates a pair of pseudoterminals and returns the registered
file descriptors in ptys. Index 0 is the primary end
(also known as master), 1 is the secondary end (also known as slave).
The syscall returns 0 on success and -1 on failure, with the
following errno:
EFAULT: ptys points to bogus memory.
EMFILE: No available file descriptor slots.