getpt() opens a pseudo-terminal master and returns its file descriptor. It is equivalent to "open(""/dev/ptmx",O_RDWR|O_NOCTTY) on Linux systems, though the pseudo-terminal master is located elsewhere on some systems that use GNU Libc.
getpt() returns an open file descriptor upon successful completion. Otherwise, it returns -1 and sets errno to indicate the error.
getpt() is specific to GNU Libc.
ptmx(4), grantpt(3), unlockpt(3), ptsname(3)