[Help-bash] Standard way to instruct executables to provide possible command line completin

[Sulaiman Mustafa]

Hello,

Is there a standard convention (GNU or otherwise) for instructing an executable 
to print possible argument completion; maybe a flag or even an environment. 
something along the lines of

theExecutable --gen-possibilities -- theExecutable partial_argum% 
# % denotes cursor position when tab completion was invoked

If not, why doesn't GNU define one? It seems to me like a very useful thing to 
have, for both developers, package maintainers, and users. Shell completion for 
an executable can be turned on with a single shell command, and developers or 
package maintainers won't need to write custom completion scripts for every 
program. If it's a matter of avoiding mixing 
user interface with machine interface, alternate methods could be used (triple 
dashes or even, if necessary, environment variables).


Sincerely,
Sulaiman

PS I apologize if this has been discussed before, but I've searched for 
information regarding this topic but to no avail.