The Unix98 specification contains three functions dealing exculisively
with pseudo-terminals:
int grantpt (int FILEDES);
int unlockpt (int FILEDES);
char *ptsname (int FILEDES);
The grantpt() function is supposed the mode and ownership of the slave
pseudo-terminal associated with master FILEDES. The user ID should be
set to the real UID of the calling process, the group ID to some
unspecified group (tty?). The permission mode should be set to 0620.
On Solaris 2.5 this is done by calling a setuid program, which is
allowed by the specification. It seems that on AIX 4.2 it is done
directly in the kernel.
The unlockpt() function is supposed to "unlock" the pseudo-terminal
associated with FILEDES.
The specification says that portable applications must call unlockpt
before openening the slave side of a pseudo-terminal device. This
suggests that it may very well be a no-op, in case no locking is needed.
The ptsname() function returns a pointer to a string wich is the name
of the slave pseudo-terminal associated with master FILEDES.
Typical usage would be something like
int master, slave;
master = open ("/dev/ptmx", ...);
grantpt (master);
unlockpt (master);
slave = open (ptsname (master), ...);
/* Do some usefull things on the pseudo-terminal. */
The name "/dev/ptmx" seems to be the standard, so I suggest to stick
with that. The standard names for the slave devices are "/dev/pts/N".
Since these three functions are three of the few remaining Unix98
functions that have not yet been implemented in glibc it would be nice
if an upcoming reimplementation of pseudo-terminals in the kernel
would provide us with the means to implement these functions.
Mark