- NetBSD Manual Pages
OPENPTY(3) NetBSD Library Functions Manual OPENPTY(3)
Powered by man-cgi (2021-06-01).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
openpty, login_tty, forkpty -- tty utility functions
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 openpty(), login_tty(), and forkpty() functions perform manipulations
on ttys and pseudo-ttys.
The openpty() function finds an available 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. The length of
name is limited to PATH_MAX as any other regular path name, so a buffer
of this size should be used. If termp is non-null, the terminal parame-
ters of the slave will be set to the values in termp. If winp is non-
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 (to the parent process
only) in amaster. The filename of the slave is returned (to both the
parent and child processes) in name if name 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.
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
openpty() will fail if:
[ENOENT] There are no available ttys.
[EPERM] The caller was not the superuser and the ptm(4) device
is missing or not configured.
login_tty() will fail if ioctl() fails to set fd to the controlling ter-
minal of the current process. forkpty() will fail if either openpty() or
NetBSD 8.0 July 27, 2012 NetBSD 8.0