nix-repl> d = derivation { name = "foo"; builder = "${bash}/bin/bash"; args = [ ./builder.sh ]; system = builtins.currentSystem; } nix-repl> :b d these derivations will be built: /nix/store/i76pr1cz0za3i9r6xq518bqqvd2raspw-foo.drv building '/nix/store/i76pr1cz0za3i9r6xq518bqqvd2raspw-foo.drv'... declare -x HOME="/homeless-shelter" declare -x NIX_BUILD_CORES="4" declare -x NIX_BUILD_TOP="/tmp/nix-build-foo.drv-0" declare -x NIX_LOG_FD="2" declare -x NIX_STORE="/nix/store" declare -x OLDPWD declare -x PATH="/path-not-set" declare -x PWD="/tmp/nix-build-foo.drv-0" declare -x SHLVL="1" declare -x TEMP="/tmp/nix-build-foo.drv-0" declare -x TEMPDIR="/tmp/nix-build-foo.drv-0" declare -x TMP="/tmp/nix-build-foo.drv-0" declare -x TMPDIR="/tmp/nix-build-foo.drv-0" declare -x builder="/nix/store/q1g0rl8zfmz7r371fp5p42p4acmv297d-bash-4.4-p19/bin/bash" declare -x name="foo" declare -x out="/nix/store/gczb4qrag22harvv693wwnflqy7lx5pb-foo" declare -x system="x86_64-linux" warning: you did not specify '--add-root'; the result might be removed by the garbage collector /nix/store/gczb4qrag22harvv693wwnflqy7lx5pb-foo this derivation produced the following outputs: out -> /nix/store/gczb4qrag22harvv693wwnflqy7lx5pb-foo