NAME

openpty, login_tty, forkpty — tty utility functions

LIBRARY

System Utilities Library (libutil, -lutil)

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

The openpty(), 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.

SEE ALSO

fork(2)