Use of snap command line in scripts / other programs

Is the snap command line tool considered suitable for use in scripts / other programs. More specifically:

  • Is the output of ‘snap’ machine parseable?
  • Is there any guarantee that it won’t change?
  • Does it make sense to add new commands that make it more easily used, e.g. snap info --installed-size only returning an integer?

Raising this due to feedback in the merge request for gnome-control-center supporting interfaces.


@robert.ancell, it’s complicated :slight_smile:

First, I have questions: why in that feedback is there talk about a “snap dependency”? is this about integrating glib-snapd? Is that seen as worse than running snap and parsing its output? How would that avoid things like the list of translations of interfaces, which snap does not (and probably will not) have? How is a dependency on an abstraction around the snapd api worse than a dependency on parsing the commandline output of a different client of the same api? I mean, you could reimplement snapd-glib for gnome-software using curl but it seems a little silly?

Second, while we do support the use of snap from scripts and the like, including the ability to use it for asynchronous operations, we can almost guarantee it’s going to change over time (with announcements via the forum, and plenty of notice, and hopefully not willy-nilly), and worse the output of snap info is still evolving. And while we do have designs for data extraction via a mini query language, and before that a simpler --format flag, we won’t be able to implement either of these any time soon. And the example you gave, which is in the per-channel part of snap info, we already know we’re going to be changing it soon (we consider it a freeform string right now, api-wise).


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Thanks, that does help - it confirms my expectations.

snapd-glib is seen as a “snap dependency”. That raises issues about it being an “official GNOME dependency” and requiring distros to ship it. I don’t see it as an issue since it’s just glue code, and installing it doesn’t require you to have snapd installed. There’s also an issue where we don’t have libflatpak in main in Ubuntu and that caused the flatpak code to move from libflatpak to using the command line. I’m currently working on getting some agreement that we can all have the glue libraries installed and the daemons optional. I think everyone who is at the code level very much wants to use libraries and not command line tools :slight_smile: