Bruno Haible wrote:
> It's because this use of '+' is easy to remember.
> "chmod +x" means "add execution permissions".
> "chmod -x" means "remove execution permissions".

To be pedantic that isn't quite true.  To be pedantic it actually is
gated by the process umask in effect at that time.  You need the 'a'
or other target in order to avoid the umask layer.

  "chmod +x" means "add execution permissions qualified by umask".
  "chmod -x" means "remove execution permissions qualified by umask".

  "chmod a+x" means "add execution permissions".
  "chmod a-x" means "remove execution permissions".

Bob