Re: Using 'system*' instead of 'system' in 'guix environment'

[ludo@gnu.org (Ludovic Courtès)]

Hi!

David Thompson <dthompson2@worcester.edu> skribis:

> In an effort to finish up a patch to add a --container flag to 'guix
> environment', I've encountered a serious problem.  The --exec flag
> allows the user to pass an arbitrary command to be run using 'system'.
> Unlike 'system*', 'system' spawns a command interpreter first and passes
> the command string in.  This is very problematic when using a container,
> because there's a very good chance that the command interpreter of the
> running Guile process is not mounted inside the container.

Oooh, good catch!

How about using something like:

  (system* (or (the-container-shell) (getenv "SHELL") "/bin/sh")
           "-c" the-string)

?

> If the above explanation is confusing, the 'sudo' program provides a
> good example of the UI I'm after:
>
>     sudo guile -c '(do-root-things)'

Or similarly: “ssh HOST some command and arguments”.

> But for now we're stuck with this:
>
>     guix environment --ad-hoc guile -E "guile -c '(do-root-things)'"
>
> Now, we can't actually do exactly what 'sudo' does because 'guix
> environment' already recognizes operands as package names, not program
> arguments.  Perhaps we can use '--' to separate the package list from
> the command to run:
>
>     guix environment --ad-hoc guile -- guile -c '(do-root-things)'
>
> Does that look okay?  Any other ideas?

I really like the UI that you propose; using -- to separate the
arguments sounds good.

I think it’s orthogonal to the question of whether to use ‘system’ or
not though.

Currently one can do things like:

  guix environment foo -E 'cd /bar ; frob'

and I think we should keep this capability, which means running the
command via /bin/sh -c (which is what ‘system’ does, but we can use
‘system*’ the way I wrote above to achieve that.)

So I think the new UI should essentially ‘string-join’ everything that
comes after --, and pass that to the procedure that invokes sh -c.

How does that sound?

Thanks for looking into it!

Ludo’.