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OPENPTY
Section: Linux Programmer's Manual (3)
Updated: 2010-06-13
Index
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NAME
openpty, login_tty, forkpty - tty 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 pseudo-terminal 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-terminal 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 pseudo-terminal.
The file
descriptor of the master side of the pseudo-terminal 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 pseudo-terminal.
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.
ERRORS
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.
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 pseudo-terminal pair;
since glibc 2.0.92,
it first attempts to open a Unix 98 pseudo-terminal pair,
and falls back to opening a BSD pseudo-terminal 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 ALSO
fork(2),
ttyname(3),
pty(7)
COLOPHON
This page is part of release 3.27 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- BUGS
-
- SEE ALSO
-
- COLOPHON
-
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