OPENPTY(3) BSD Library Functions Manual OPENPTY(3)NAME
openpty, login_tty, forkpty — tty utility functions
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 allocates a pseudo-tty and returns file descrip‐
tors for the master and slave in amaster and aslave. If name is non-
null, the filename of the slave is returned in name. 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
creates a new process operating in a pseudo-tty. The file descriptor of
the master side of the pseudo-tty is returned in amaster, and the file‐
name of the slave in name if it is non-null. The termp and winp parame‐
ters, 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.
ERRORSopenpty() will fail if:
[EAGAIN] There are no available pseudo-ttys.
login_tty() will fail if ioctl() fails to set fd to the controlling ter‐
minal of the current process. forkpty() will fail if either openpty() or
fork() fails.
FILES
/dev/ptmx cloning pseudo-tty device
/dev/ttys[0-9][0-9][0-9] slave pseudo-tty devices
SEE ALSOfork(2)BSD April 5, 2008 BSD
