Re: Toward 0.2

[ludo@gnu.org (Ludovic Courtès)]

Nikita Karetnikov <nikita@karetnikov.org> skribis:

>> It’s not needed.  All that needed is the name of the executable file
>> to wrap.
>
> I don't understand.  How will 'rename-file' get the location of the
> executable?  For example:
>
> (wrap-program "wget" [...])
>
> I guess that it will only work if you invoke 'wrap-program' from the
> same directory.

Yes, and that’s what we want.

However, the ‘exec’ line in the wrapper needs the absolute file name.
For that it can do along the lines of:

  (string-append "exec " (canonicalize-path file))

>> For the case where there are have several variables you want to set.
>
> Could you provide an example?  The following works without '#:rest':
>
> (display (wrap-program "wget" '(("PATH" ":" = ("/nix/.../gawk/bin"))
>                                 ("CERT_PATH" ":" suffix ("/nix/.../share/certs"
>                                                          "/nix/.../foo/certs")))))

Yeah there are two choices: two required arguments (like above), where
the second one is a list, or one required argument and one rest
argument.

In the latter case, you would instead do:

  (wrap-program "wget" '("PATH" ":" = ("/nix/.../gawk/bin"))
                       '("CERT_PATH" ":" suffix ("/nix/.../share/certs"
                                                 "/nix/.../foo/certs")))

I tend to prefer this form because it may be more concise in common
cases.

HTH,
Ludo’.