Manual browser: ptm(4)

PTM(4) Kernel Interfaces Manual PTM(4)


ptmpseudo-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.


ptm access device
ptm cloning device, used to implement Unix98 ptys


The /dev/ptm device appeared in OpenBSD 3.5 and was ported to NetBSD 3.0.
November 30, 2013 NetBSD 7.0