openpty()

NAME

openpty(), forkpty - open pseudo terminal

SYNOPSIS

#include <sys/types.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <pty.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)

The function openpty() attempts to obtain the next pseudo terminal from the system (see pty(4)). If it successfully finds one, it subsequently tries to change the ownership of the subordinate (also called slave) device to the real user identifier (UID) of the current process, the group membership to the group tty (if such a group exists in the system), the access permissions for reading and writing by the owner, and for writing by the group.

If the argument name is not NULL, openpty() copies the path name of the subordinate 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 side of the pty and the subordinate side of the pty are returned in the locations pointed to by amaster and aslave, respectively.

The forkpty() function first calls openpty() to obtain the next available pseudo terminal 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 prepares the subordinate side for a new login session. In the parent process, it closes the descriptor for the subordinate side of the pty. The arguments amaster, name, termp, and winp have the same meaning as described for openpty().

RETURN VALUES

The openpty() function returns 0 on success, or -1 on failure.

The forkpty() function returns -1 on failure, or on success, returns 0 in the subordinate process, and the process ID of the child 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 described for fork(2).

NOTES

The calling process must have an effective UID of superuser 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 and, in the case of forkpty(), create the new process.