Support background commands in custom actions

[nohajc]

@nohajc, would it be possible to use custom action to trigger background command? It would be nice way to "implement" what is needed here

Originally posted by @kapitainsky in #100

One potential use case would be to periodically "touch" a file on a mounted drive in order to prevent power saving mode of the USB peripheral.

[kapitainsky]

One potential use case would be to periodically "touch" a file on a mounted drive in order to prevent power saving mode of the USB peripheral.

And many others like for example to take subvolume snapshot on BTRFS filesystem. However more complex actions like for example trimming existing snapshots based on some logic require more than one liner.

What would be nice is to be able to run longer scripts.

[nohajc]

I already have #80. That's what you mean, right?

[kapitainsky]

I already have #80. That's what you mean, right?

Yeap. OK so it is already tracked.

In general if one command is allowed than it should be also possible to run some scripts. This way even complex and conditional operations can be implemented.

[nohajc]

Yes, when I say command, I mean it in the broader sense. All custom action hooks are already invoked in a shell, so you're able to use multiple commands, pipes, redirection, etc.