OPENPTY(3) Linux Programmer's Manual OPENPTY(3)NAME
openpty, login_tty, forkpty - terminal utility functions
SYNOPSIS
#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.
DESCRIPTION
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 terminal 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 stan‐
dard input, output, and error streams of the current process, and clos‐
ing fd.
The forkpty() function combines openpty(), fork(2), and login_tty() to
create a new process operating in a pseudoterminal. The file descrip‐
tor 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.
RETURN VALUE
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.
ERRORSopenpty() will fail if:
ENOENT There are no available terminals.
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.
CONFORMING TO
These are BSD functions, present in libc5 and glibc2. They are not
standardized in POSIX.
NOTES
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.
BUGS
Nobody knows how much space should be reserved for name. So, calling
openpty() or forkpty() with non-NULL name may not be secure.
SEE ALSOfork(2), ttyname(3), pty(7)COLOPHON
This page is part of release 3.54 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)
