> The 1st value returned by (subprocess) is an opaque reference to the > executing process. If you pass the reference to (subprocess-status) it > will return *'running* if the process currently is executing, or the > exit/error value. >
"exit/error value" is the issue there. (subprocess-status ps) will return 'running if the process is running. If it doesn't, either the process has never ran, either it has finished with a exit code. No way (that I see) to disambiguate. > No actual process can have pid 0 ... that value is reserved (on > Unix/Linux and Windows). > > Racket doesn't support fork (because Windows doesn't), but recall that > when you fork in Unix/Linux, the child process receives the illegal pid > value 0 so that it knows it is the child, while the parent receives the > real pid value for the child. > > Also note that (subprocess-pid) will be valid only if the process started > successfully. > > (subprocess-pid) is only valid when (subprocess-status) is 'running but testing the status then requesting the pid is not atomic, therefore subprocess-pid should return #f or raise. Or return pid 0 but it should be documented :) By the way there is a process with pid 0 on Linux, it's "sched". And on Windows, its "idle". Of course it could never be the result of (subprocess ...) but I don't want to rely on incidental behaviour from an API := > Hope this helps, > George > Thanks for contributing, it's much appreciated, Bertrand -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/f91e532a-182f-454e-8495-496a9c088e9f%40googlegroups.com.
