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PTM(4) Device Drivers Manual PTM(4)

ptm — pseudo-terminal multiplexor device

pseudo-device pty

The ptm driver is the backend for the /dev/ptm device. It supports three ioctl(2)s. The first is TIOCPTMGET, which allocates a free pseudo-terminal device, sets its user ID to the calling user, revoke(2)s it, and returns the opened file descriptors for both the master and the slave pseudo-terminal device to the caller in a struct ptmget. This struct has the following content: 
struct ptmget {
        int     cfd;
        int     sfd;
        char    cn[PATH_MAX];
        char    sn[PATH_MAX];
};

where cfd and sfd contain the master resp. slave device's file descriptor and cn and sn the corresponding paths in the file system.

The /dev/ptmx device supports two more ioctl(2)s, TIOCGRANTPT, which is used by grantpt(3), TIOCPTSNAME, which is used by ptsname(3).

The ptm device is included with the pseudo-device pty(4). It can be disabled by adding “options NO_DEV_PTM” to the kernel configuration.

/dev/ptm
ptm access device
/dev/ptmx
ptm cloning device, used to implement Unix98 ptys

grantpt(3), openpty(3), posix_openpt(3), ptsname(3), unlockpt(3), pty(4)

The /dev/ptm device appeared in OpenBSD 3.5 and was ported to NetBSD 3.0.

November 30, 2013 NetBSD-9.2