When writing custom service actions, you may find it useful to spawn
helper processes. The (shepherd service) module provides helpers
that are safe to use within the shepherd process.
See the nginx example, for a typical use case.
Run command and return its exit status, which can be examined with
status:exit-val and related procedures (see Processes in GNU Guile Reference Manual).
This works exactly like the system and system* procedures
provided by Guile but the shepherd process redefines them so
they cooperate with its own even loop and child process termination
handling.
Like system*, spawn command (a list of strings) and return
its exit status. Additionally accept the same keyword arguments as
fork+exec-command: #:user, #:directory, and so on.
fork+exec-command.