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OPENPTY(3)                              BSD Library Functions Manual                              OPENPTY(3)

NAME
     openpty, login_tty, forkpty -- tty utility functions

SYNOPSIS
     #include <util.h>

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

     int
     login_tty(int fd);

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

DESCRIPTION
     The openpty(), login_tty(), and forkpty() functions perform manipulations on ttys and pseudo-ttys.

     The openpty() function allocates a pseudo-tty and returns file descriptors for the master and slave in
     amaster and aslave.  If name is non-null, the filename of the slave is returned in name.  If termp is
     non-null, the terminal parameters of the slave will be set to the values in termp.  If winp is non-null, nonnull,
     null, the window size of the slave will be set to the values in winp.

     The login_tty() function prepares for a login on the tty fd (which may be a real tty device, or the
     slave of a pseudo-tty as returned by openpty()) by creating a new session, making fd the controlling
     terminal for the current process, setting fd to be the standard input, output, and error streams of the
     current process, and closing fd.

     The forkpty() function combines openpty(), fork(), and login_tty() to creates a new process operating
     in a pseudo-tty.  The file descriptor of the master side of the pseudo-tty is returned in amaster, and
     the filename of the slave in name if it is non-null.  The termp and winp parameters, if non-null, will
     determine the terminal attributes and window size of the slave side of the pseudo-tty.

RETURN VALUES
     If a call to openpty(), login_tty(), or forkpty() is not successful, -1 is returned and errno is set to
     indicate the error.  Otherwise, openpty(), login_tty(), and the child process of forkpty() return 0,
     and the parent process of forkpty() returns the process ID of the child process.

ERRORS
     openpty() will fail if:

     [EAGAIN]           There are no available pseudo-ttys.

     login_tty() will fail if ioctl() fails to set fd to the controlling terminal of the current process.
     forkpty() will fail if either openpty() or fork() fails.

FILES
     /dev/ptmx                 cloning pseudo-tty device
     /dev/ttys[0-9][0-9][0-9]  slave pseudo-tty devices

SEE ALSO
     fork(2)

BSD                                             April 5, 2008                                            BSD