NAME
openpty, login_tty, forkpty - tty utility functions
SYNOPSIS
#include <pty.h>
I int openpty(int * amaster , int * aslave , char * name ,
I struct termios * termp , struct winsize * winp );
I pid_t forkpty(int * amaster , char * name , struct termios * termp ,
I struct winsize * winp );
#include <utmp.h>
I int login_tty(int fd );
Link with -lutil.
DESCRIPTION
The
R openpty ()
function finds an available pseudo-terminal and returns file descriptors
for the master and slave in
amaster
and
R aslave .
If
name
is not NULL, the filename of the slave is returned in
R name .
If
termp
is not NULL, the terminal parameters of the slave will be set to the
values in
R termp .
If
winp
is not NULL, the window size of the slave will be set to the values in
R winp .
The
R 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
R openpty ())
by creating a new session, making
fd
the controlling terminal for the current process, setting
fd
to be the standard input, output, and error streams of the current
process, and closing
R fd .
The
R forkpty ()
function combines
R openpty (),
fork(2),
and
R 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
R amaster ,
and the filename of the slave in
name
if it is not NULL.
The
termp
and
winp
parameters, 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
R openpty (),
R login_tty (),
or
R forkpty ()
is not successful, -1 is returned and
errno
is set to indicate the error.
Otherwise,
R openpty (),
R login_tty (),
and the child process of
R forkpty ()
return 0, and the parent process of
R forkpty ()
returns the process ID of the child process.
ERRORS
R openpty ()
will fail if:
ENOENT
There are no available ttys.
R login_tty ()
will fail if
ioctl(2)
fails to set
fd
to the controlling terminal of the current process.
R forkpty ()
will fail if either
R openpty ()
or
fork(2)
fails.
CONFORMING TO
These are BSD functions, present in libc5 and glibc2.
NOTES
In versions of glibc before 2.0.92,
R 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
R name .
So, calling
R openpty ()
or
R forkpty ()
with non-NULL
name
may not be secure.
SEE ALSO
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