New hook type "process" has been added to WeeChat. You can use it in C plugins, and all scripts languages (perl, python, ruby, lua and tcl).

It runs a command with fork, and send you result (return code, stdout and stderr) via a callback, when command has ended, or if WeeChat output buffer is full (then it will be partial result of command). There is optional timeout (in milliseconds), to kill process if it's still running after given time.

The script shell.py has been updated to use that new hook.