Le 13/12/2020 à 03:15, Steve Litt a écrit :
> On Fri, 11 Dec 2020 15:53:35 +0100
> Didier Kryn <kryn@???> wrote:
>
>
>>     I don't make it an argument against xdm. Just cheating about your
>> own arguments (~:
> Didier, why didn't you make that suggestion to me 15 years ago? It's a
> brilliant way to guarantee that if somebody logs out of X, they have no
> logged in shell to make mischief with.
>
> I should have thought of that myself. 15 years ago :-).
>
    Yes you should have. But this is something everybody forgets all the
time. We all imagine a program invocation like a function call, in which
the caller is suspended until the callee returns; but actually when the
shell is suspended waiting the application to return, it intentionnally
waits, but can easily stop waiting. The artefact is that we must add an
'&' to tell it not to wait in the first place. This is a semantic sugar
to make it behave by default "as if" it was a function call.

    exec does not create a new process; instead it substitutes the new
application to the current one (the shell). I had fun some years ago
writing an application which opened an http connection to a server on
standard input, read the http header, and then execed another
application given in argument.

--             Didier