Where should the builder script be located for a stand-alone nix expression?

Question

I have a nix expression file (.nix) and a shell script builder, specified like:

stdenv.mkDerivation rec {
    name = "my-env";
    builder = './my-builder.sh';
    ...

./my-builder.sh: No such file or directory when I run nix-build ./my-env.nix; the nix expression file and builder scripts are sitting side-by-side in my home directory.

My intent is to use this nix expression file to prepare an environment using nix-build and then to actually quickly run the environment whenever I want to use it (using nix-shell).

EDIT: I just noticed that nix-shell ./ my-env.nix works fine; so far I'm not actually building anything, so I should probably just omit the builder.

EDIT#2: My concrete example is the following:

This line puts both the nix expression and the builder in the same directory. This other line uses nix-shell to prepare the environment, but I assume a similar nix-build command could be used (especially if one wanted to install a custom package as part of the environment, but maybe that is not very idiomatic in Nix)

Solution

Quotes around the builder's path were apparently a no-no. I ended up having other issues, and pieced this together to eventually get the thing to run:

builder = builtins.toFile "builder.sh" ''
  source $stdenv/setup
  mkdir -p $out
  echo "" > $out/Done
  echo "Done setting up Scala environment."
'';

Answer 1

Try putting a semicolon at the end of the line and removing the single quotes:

builder = ./my-builder.sh;

Then double-check to make sure my-builder.sh is in the same directory as the .nix file where you wrote that.