Name
openpty, login_tty, forkpty — tty utility functions
Synopsis
#include <pty.h>
int
openpty( |
int * | amaster, |
| int * | aslave, | |
| char * | name, | |
| struct termios * | termp, | |
| struct winsize * | winp); |
pid_t
forkpty( |
int * | amaster, |
| char * | name, | |
| struct termios * | termp, | |
| struct winsize * | winp); |
#include <utmp.h>
int
login_tty( |
int | fd); |
![[Note]](../stylesheet/note.png) |
Note |
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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 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 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.
NOTES
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.