Does nix provide package options / parameters? How do I list them?

Question

For example I can query for available package versions of llvm:

$ nix-env -qa llvm
...
llvm-4.0.1
llvm-5.0.2
llvm-6.0.1

With homebrew I can provider an option when installing a package like llvm, in this case the --shared option:

$ brew install llvm --shared

Does nix support providing package specific options like this? Is there a way to list the available options of a package?

Answer 1

Yes, nix derivations can come with optional arguments. For example, the derivation for LLVM 6 nixpkgs/development/compilers/llvm/6/llvm.nix starts like this:

{ stdenv
, fetch
...
, zlib
, debugVersion ? false
, enableManpages ? false
, enableSharedLibraries ? true
, enableWasm ? true
, darwin
}:

You can supply values for these arguments on the nix-env command line using the options --arg or --argstr, compare the man page. E.g.,

nix-env -iA nixpkgs.llvm --arg enableSharedLibraries false

I'm not aware of an easier way to find out such options than to read the nixpkgs source, unfortunately.