:man| Alphabetical   Categories   About us 
OPENPTY (3) | C library functions | Unix Manual Pages | :man


openpty, login_tty, forkpty - tty utility functions




#include <pty.h> /* for openpty and forkpty */
#include <utmp.h> /* for login_tty */

"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);


The openpty() function finds an available pseudo-tty 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 parameters 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 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 create 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 not NULL. The termp and winp parameters, if not NULL, will determine the terminal attributes and window size of the slave side of the pseudo-tty.


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() will fail if:
ENOENT There are no available ttys.
login_pty() 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.


These functions are included in libutil, hence you’ll need to add -lutil to your compiler commandline.




These are BSD functions, present in libc5 and glibc2.


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



Created by Blin Media, 2008-2013