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OPENPTY(3) Linux Programmer's Manual OPENPTY(3)
openpty, login_tty, forkpty - tty utility functions
#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);
Link with -lutil.
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 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 pseudoterminal as returned by openpty()) by
creating a new session, making fd the controlling 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. The file descriptor of the
master side of the pseudoterminal is returned in amaster, and the filename of
the slave in name if it is not NULL. The termp and winp arguments, if not
NULL, will determine the terminal 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() will fail if:
ENOENT There are no available ttys.
login_tty() will fail if ioctl(2) fails to set fd to the controlling terminal
of the calling process.
forkpty() will fail if either openpty() or fork(2) fails.
These are BSD functions, present in libc5 and glibc2. They are not
standardized in POSIX.
The const modifiers were added to the structure pointer arguments of openpty()
and forkpty() in glibc 2.8.
In versions of glibc before 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 secure.
fork(2), ttyname(3), pty(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-06-13 OPENPTY(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface