openpty(3)                                            Library Functions Manual                                           openpty(3)

       openpty, login_tty, forkpty - terminal utility functions

       System utilities library (libutil, -lutil)

       #include <pty.h>

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

       #include <utmp.h>

       int login_tty(int fd);

       The  openpty()  function  finds an available pseudoterminal and returns file descriptors for the master and slave in amaster
       and aslave.  If name is not NULL, the filename of the slave is returned in name.  If termp is not NULL, the terminal parame‐
       ters  of the slave will be set to the values in termp.  If winp is not 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 terminal referred to by the file descriptor fd (which  may  be  a  real
       terminal  device,  or  the slave of a pseudoterminal as returned by openpty()) by creating a new session, making fd the con‐
       trolling terminal for the calling 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(2), and login_tty() to create a new process operating in a pseudoterminal.
       A file descriptor referring to master side of the pseudoterminal is returned in amaster.  If name is not NULL, the buffer it
       points to is used to return the filename of the slave.  The termp and winp arguments, if not NULL, will determine the termi‐
       nal attributes and window size of the slave side of the pseudoterminal.

       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.

       openpty() fails if:

       ENOENT There are no available terminals.

       login_tty() fails if ioctl(2) fails to set fd to the controlling terminal of the calling process.

       forkpty() fails if either openpty() or fork(2) fails.

       For an explanation of the terms used in this section, see attributes(7).

       │Interface                                                                         │ Attribute     │ Value                  │
       │forkpty(), openpty()                                                              │ Thread safety │ MT-Safe locale         │
       │login_tty()                                                                       │ Thread safety │ MT-Unsafe race:ttyname │

       These are BSD functions, present in glibc.  They are not standardized in POSIX.

       The const modifiers were added to the structure pointer arguments of openpty() and forkpty() in glibc 2.8.

       Before glibc 2.0.92, openpty() returns file descriptors for a BSD pseudoterminal pair; since glibc 2.0.92, it first attempts
       to open a UNIX 98 pseudoterminal pair, and falls back to opening a BSD pseudoterminal pair if that fails.

       Nobody  knows  how much space should be reserved for name.  So, calling openpty() or forkpty() with non-NULL name may not be

       fork(2), ttyname(3), pty(7)

Linux man-pages 6.03                                         2022-12-15                                                  openpty(3)