o Multithreaded processes may not work. Not tested. May work. May not
  work.

o Processes with several different open ptys may not be wrapped
  correctly. (Escape-Sequences are not captured correcly)

o SUID/SGID processes are ignored. This is not a bug, it's a
  feature. Because of security considerations the Linux dynamic loader
  ignores LD_PRELOAD on SUID/SGID executables.

  This includes xterm. (But may be ignored since all you need to do to
  catch all beeps is to preload the library for the shell in the xterm)
