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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
OPENPTY(3) Linux Programmer's Manual OPENPTY(3)
openpty, login_tty, forkpty - terminal 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 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 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. If name is not NULL, the buffer it points to is used to
return the the filename of the slave. 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 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.
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.
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 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2015-04-19 OPENPTY(3)
Pages that refer to this page: pty(7)