[wellylug] Non-console Beep for linux ?

[Mark Robinson]

Tony Wills wrote:
> 
> Does anyone know of a small linux program to beep the built in PC 
> speaker that doesn't need the console device?  (ie not echo -e "\a")
> 

 From man beep :

IOCTL WACKINESS

Some users will encounter a situation where beep dies with a complaint 
from ioctl().  The reason for this, as Peter Tirsek was nice enough to 
point out to me, stems from how the kernel handles beep's attempt to 
poke at (for non-programmers: ioctl is a sort of catch-all function that 
lets you poke at things that have no other predefined poking-at 
mechanism) the tty, which is how it beeps.  The short story is, the 
kernel checks that either:

        - you are the superuser

        - you own the current tty

What  this means is that root can always make beep work (to the best of 
my knowledge!), and that any local user can make beep work, BUT a 
non-root remote user cannot use beep in it's natural state.  What's 
worse, an xterm, or other x-session counts, as far as the kernel is 
concerned, as 'remote', so beep won't  work from a non-priviledged xterm 
either.  I had originally chalked this up to a bug, but there's actually 
nothing I can do about it, and it really is a Good Thing that the kernel 
does things this way.  There is also a solution.

By default beep is not installed with the suid bit set, because that 
would just be zany. On the other hand, if you do make it suid root, all 
  your problems with beep bailing on ioctl calls will magically vanish, 
which is pleasant, and the only reason not to is that any suid program 
is a potential security hole.

Conveniently, beep is very short, so auditing it is pretty straight forward.

Decide for yourself, of course, but it looks safe to me - there's only 
one buffer and fgets doesn't let it overflow, there's only one file 
opening, and  while there  is  a  potential race condition there, it's 
with /dev/console.  If someone can exploit this race by replacing 
/dev/console, you've got bigger problems. :)

So the quick, only, and likely safe solution if beep is not beeping when 
you want it to is (as root):

        # chmod 4755 /usr/bin/beep

        (or wherever you put it)

he one snag is that this will give any little nitwit the ability to run 
beep successfully - make sure this is what you want. If it isn't, a 
slightly more complex fix would be something like:

        # chgrp beep /usr/bin/beep

        # chmod 4750 /usr/bin/beep

and then add only beep-worthy users to the 'beep' group.



Hope that helps
Mark