NAME
openpty,
login_tty, forkpty —
tty utility functions
LIBRARY
library “libutil”
SYNOPSIS
#include
<util.h>
int
openpty(int
*amaster, int
*aslave, char
*name, struct termios
*termp, struct winsize
*winp);
int
login_tty(int
fd);
pid_t
forkpty(int
*amaster, char
*name, struct termios
*termp, struct winsize
*winp);
DESCRIPTION
Theopenpty(),
login_tty(), and forkpty()
functions perform manipulations on ttys and pseudo-ttys.
The
openpty()
function finds an available pseudo-tty and returns file descriptors for the
master and slave in amaster and
aslave. If name is non-null, the
filename of the slave is returned in name. The length
of name is limited to PATH_MAX
as any other regular path name, so a buffer of this size should be used. If
termp is non-null, the terminal parameters of the
slave will be set to the values in termp. If
winp is non-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-tty as returned by
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 fd.
The
forkpty()
function combines openpty(),
fork(),
and login_tty() to create a new process operating in
a pseudo-tty. The file descriptor of the master side of the pseudo-tty is
returned (to the parent process only) in amaster. The
filename of the slave is returned (to both the parent and child processes)
in name if name is non-null. The
termp and winp parameters, if
non-null, will determine the terminal attributes and window size of the
slave side of the pseudo-tty.
RETURN VALUES
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.
FILES
- /dev/[pt]ty[p-zP-T][0-9a-zA-Z]
ERRORS
openpty() will fail if:
- [
ENOENT] - There are no available ttys.
- [
EPERM] - The caller was not the superuser and the ptm(4) device is missing or not configured.
login_tty() will fail if
ioctl() fails to set fd to the
controlling terminal of the current process.
forkpty() will fail if either
openpty() or fork()
fails.