openpty
Section: C Library Functions (3)
Updated: 202-0-17
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NAME
openpty, login_tty, forkpty - terminal utility functions
LIBRARY
System utilities library
(
libutil,~
-lutil)
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);
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
referred to by the file descriptor
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.
A file descriptor referring to
master side of the pseudoterminal is returned in
amaster.
If
name
is not NULL, the buffer it points to is used to return 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.
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()
fails if:
- ENOENT
-
There are no available terminals.
login_tty()
fails if
ioctl(2)
fails to set
fd
to the controlling terminal of the calling process.
forkpty()
fails if either
openpty()
or
fork(2)
fails.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
forkpty(),
openpty()
| Thread safety | M-Safe locale
|
|
login_tty()
| Thread safety | M-Unsafe race:ttyname
|
STANDARDS
BSD.
HISTORY
The
const
modifiers were added to the structure pointer arguments of
openpty()
and
forkpty()
in glibc 2.8.
Before glibc 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 no-NULL
name
may not be secure.
SEE ALSO
fork(2),
ttyname(3),
pty(7)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- STANDARDS
-
- HISTORY
-
- BUGS
-
- SEE ALSO
-
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