PTY(3) BSD Library Functions Manual PTY(3)NAME
openpty, forkpty — auxiliary functions to obtain a pseudo-terminal
LIBRARY
System Utilities Library (libutil, -lutil)
SYNOPSIS
#include <sys/types.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <libutil.h>
int
openpty(int *amaster, int *aslave, char *name, struct termios *termp,
struct winsize *winp);
int
forkpty(int *amaster, char *name, struct termios *termp,
struct winsize *winp);
DESCRIPTION
The function openpty() attempts to obtain the next available pseudo-ter‐
minal from the system (see pty(4)). If it successfully finds one, it
subsequently tries to change the ownership of the slave device to the
real UID of the current process, the group membership to the group “tty”
(if such a group exists in the system), the access permissions for read‐
ing and writing by the owner, and for writing by the group, and to inval‐
idate any current use of the line by calling revoke(2).
If the argument name is not NULL, openpty() copies the pathname of the
slave pty to this area. The caller is responsible for allocating the
required space in this array.
If the arguments termp or winp are not NULL, openpty() initializes the
termios and window size settings from the structures these arguments
point to, respectively.
Upon return, the open file descriptors for the master and slave side of
the pty are returned in the locations pointed to by amaster and aslave,
respectively.
Forkpty() first calls openpty() to obtain the next available pseudo-ter‐
minal from the system. Upon success, it forks off a new process. In the
child process, it closes the descriptor for the master side of the pty,
and calls login_tty(3) for the slave pty. In the parent process, it
closes the descriptor for the slave side of the pty. The arguments
amaster, name, termp, and winp have the same meaning as described for
openpty().
RETURN VALUESOpenpty() returns 0 on success, or -1 on failure.
Forkpty() returns -1 on failure, 0 in the slave process, and the process
ID of the slave process in the parent process.
ERRORS
On failure, openpty() will set the global variable errno to ENOENT.
In addition to this, forkpty() may set it to any value as described for
fork(2).
SEE ALSOchmod(2), chown(2), fork(2), getuid(2), open(2), revoke(2), login_tty(3),
pty(4), termios(4), group(5)BUGS
The calling process must have an effective UID of super-user in order to
perform all the intended actions. No notification will occur if
openpty() or forkpty() failed to proceed with one of the described steps,
as long as they could at least allocate the pty at all (and create the
new process in the case of forkpty()).
BSD December 29, 1996 BSD
