PTY(3) BSD Library Functions Manual PTY(3)NAME
openpty, forkpty — auxiliary functions to obtain a pseudo-terminal
System Utilities Library (libutil, -lutil)
openpty(int *amaster, int *aslave, char *name, struct termios *termp,
struct winsize *winp);
forkpty(int *amaster, char *name, struct termios *termp,
struct winsize *winp);
The function openpty() attempts to obtain the next available pseudo-ter‐
minal from the system (see pty(4)). If it successfully finds one, it
subsequently changes the ownership of the slave device to the real UID of
the current process, the group membership to the group “tty” (if such a
group exists in the system), the access permissions for reading and writ‐
ing by the owner, and for writing by the group, and invalidates any cur‐
rent use of the line by calling revoke(2).
If the argument name is not NULL, openpty() copies the pathname of the
slave pty to this area. The caller is responsible for allocating the
required space in this array.
If the arguments termp or winp are not NULL, openpty() initializes the
termios and window size settings from the structures these arguments
point to, respectively.
Upon return, the open file descriptors for the master and slave side of
the pty are returned in the locations pointed to by amaster and aslave,
The forkpty() function first calls openpty() to obtain the next available
pseudo-terminal from the system. Upon success, it forks off a new
process. In the child process, it closes the descriptor for the master
side of the pty, and calls login_tty(3) for the slave pty. In the parent
process, it closes the descriptor for the slave side of the pty. The
arguments amaster, name, termp, and winp have the same meaning as
described for openpty().
The openpty() function returns 0 on success, or -1 on failure.
The forkpty() function returns -1 on failure, 0 in the slave process, and
the process ID of the slave process in the parent process.
The openpty() function may fail and set the global variable errno for any
of the errors specified for the grantpt(3), posix_openpt(3), ptsname(3),
and unlockpt(3) functions and the revoke(2) system call.
In addition to this, forkpty() may set it to any value as described for
SEE ALSOchmod(2), chown(2), fork(2), getuid(2), open(2), revoke(2), login_tty(3),
pty(4), termios(4), group(5)BSD December 29, 1996 BSD