PTY(3)                 FreeBSD Library Functions Manual                 PTY(3)

NAME
     openpty, forkpty - auxiliary functions to obtain a pseudo-terminal

LIBRARY
     System Utilities Library (libutil, -lutil)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ioctl.h>
     #include <termios.h>
     #include <libutil.h>

     int
     openpty(int *amaster, int *aslave, char *name, struct termios *termp,
         struct winsize *winp);

     int
     forkpty(int *amaster, char *name, struct termios *termp,
         struct winsize *winp);

DESCRIPTION
     The function openpty() attempts to obtain the next available pseudo-
     terminal 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
     writing by the owner, and for writing by the group, and invalidates any
     current 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,
     respectively.

     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().

RETURN VALUES
     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.

ERRORS
     The openpty() function may fail and set the global variable errno for any
     of the errors specified for the grantpt(3), posix_openpt(2), 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
     fork(2).

SEE ALSO
     chmod(2), chown(2), fork(2), getuid(2), open(2), revoke(2), login_tty(3),
     pty(4), termios(4), group(5)

HISTORY
     The openpty() and forkpty() functions first appeared in 4.3BSD-Reno.

BUGS
     openpty() writes the slave terminal's name to name, but does not check
     that sufficient space is available.  It is advisable to use ptsname(3)
     instead.

FreeBSD 13.1-RELEASE-p6          June 2, 2018          FreeBSD 13.1-RELEASE-p6