Control stript which is runing in background.

[Cameron Simpson]

On 31Dec2020 18:07, jak <nospam at please.ty> wrote:
>Il 31/12/2020 11:43, Petro ha scritto:
>>I would like to make something like this:
>>A python script would run headlessly in the background.
>>I would like to control the script from the command line using other python scripts or from the python shell.
>> From time to time I would ask the main script to create a popup window with an image or a plot.
>>What would be the proper way to approach it. How to make communication between two scripts?
>
>using named pipes would be an alternative. A small example that 
>produces an echo for windows.

A Windows named pipe seems to be more like a UNIX-side "UNIX domain 
socket" than a UNIX side "named pipe".

>For linux it's simpler using os.mkfifo:

Not really. For Linux (and of course other UNIXen) you really want a 
UNIX domain socket, not a a name pipe (as from mkfifo).

The reason is that a socket (and a Windows pipe, from my limited 
understanding) creates a new distinct connection when you open it. (The 
other end has to accept that connection, at least in UNIX).

The problem with a UNIX pipe is that every client (your command line 
control script) _share_ the same pipe - if two scripts un at once there 
will be a failure. If you contrive some locking scheme then you can 
share a named pipe in UNIX because only once client will use the pipe at 
a time.

Just something to keep in mind.

Cheers,
Cameron Simpson <cs at cskk.id.au>