Re: Find location of installed package in /gnu/store

[Edouard Klein <edou@rdklein.fr>]

Hi !

This is where G-expressions will help you :)

Basically the path you need does not exist in the same "strata" as the
code of the package.

The following code will define a build-gexp function that evaluates a
G-expression and prints the resulting directory in the store. You can
try it in "guix repl" or with "guix build -f FILE"

https://guix.gnu.org/manual/en/guix.html#G_002dExpressions

A G-exp begins with #~ and withing the following expr, any piece of code
prefixed by #$ is recursively replaced by its value, but only if this
value is a primitive value (string, int,...) or a package.

If it is a package, it gets replaced by the path in the store of that
package.

So to give a short answer, run the following into the REPL to get your
path:
  (use-modules
     (guix gexp)
     (guix store)
     (guix derivations)
     (gnu packages java))
    (define (build-gexp gexp)
      "Build GEXP using the local daemon."
      (let ((derivation 
             (run-with-store (open-connection)
               (gexp->derivation
                "noname"
                gexp))))
        (build-derivations
         (open-connection)
         (list derivation))
        (derivation-output-path (assoc-ref (derivation-outputs derivation) "out"))))

(build-gexp
 (with-imported-modules '((guix build utils))
   #~(begin
       (use-modules (guix build utils))
       (mkdir-p  (string-append #$output "/bin"))
       (with-output-to-file (string-append #$output "/bin/helloworld.sh")
         (lambda _
           (display (string-append "Iced tea lives at:" #$icedtea-8)))))))


This wil output a path, in my case
/gnu/store/vv5sc5l488xxysyz88aadjj3fwnqr2xa-noname

and in it you'll have the file:
/gnu/store/vv5sc5l488xxysyz88aadjj3fwnqr2xa-noname/bin/helloworld.sh

which contains
Iced tea lives at:/gnu/store/vaqdvsqdv5mads38dp6pc5827pdgnmb3-icedtea-3.7.0

Given your stated use case, you may be interested in the following
upcoming patch:
https://issues.guix.gnu.org/48277

It will let you wrap any executable in the appropriate env vars, so I
guess you will be able to do something like
#$(wrap-in-search-paths #~(string-append #$output "/bin/your-script")
(list icedtea-8))

Hopefully icedtea-8 sets the correct search paths, but I believe it
does.

Cheers,

Edouard.

Phil Beadling writes:

> Hi,
>
> Given a package definition, eg icedtea-8's JDK, how can can I determine the
> location of the installed package in my /gnu/store?
>
> There doesn't seem to be anything on the package module itself, presumably
> because this is static data, and what I need is something to calculate the
> hash of the resulting install specific to my Guix?
>
> eg
> scheme@(guix-user) [3]> (package-outputs icedtea-8)
> $8 = ("out" "jdk" "doc")
> scheme@(guix-user) [3]>
>
> I'd like to return this location using the package name or definition as an
> input:
> /gnu/store/i3vf1a49m0abcjqza19mb4mkjmc6k60n-icedtea-3.7.0-jdk/
>
> The aim is to use this to derivive the JDK include directories in a generic
> way for some scripts I'm writing, such that I don't need to update them
> each time the JDK hash changes after a guix pull.
>
> Cheers,
> Phil.