In a lorri shell:
$ echo $PATH
/nix/store/2xv7ha3rsc8cd06hyajmhys91fnir3xg-clang-wrapper-7.1.0/bin /nix/store/adp1mzm4hwqnjff606xy4sf1vkjrb27m-clang-7.1.0/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/jd73bpkss4lcrkmyqv81vbvm5in9c31g-cctools-binutils-darwin-wrapper-927.0.2/bin /nix/store/3b45vydqz1id9592v1f4csgcrxhq3xpd-cctools-binutils-darwin-927.0.2/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/nx9prqq9wpf555vlkc2wvblpnx9gjqph-findutils-4.7.0/bin /nix/store/c6m2442wbvcflsx33ybwf72c6sgr0460-diffutils-3.7/bin /nix/store/1lkinwnij0hdvmwfdxjcjb3wkcy3ysmh-gnused-4.8/bin /nix/store/y1wqnjcly40hpkwbfyd5pdinv8k5gyr8-gnugrep-3.4/bin /nix/store/s2gzkzg22m8jg0nbgza4jz0vbs77sgzp-gawk-5.0.1/bin /nix/store/s6hzqm5ma4jhif2gbc6slbw0a61rh99q-gnutar-1.32/bin /nix/store/0b7hgdzd8k72m10q76rrqfgscan7qgcv-gzip-1.10/bin /nix/store/d1p77cf3aq8frq903dhd1ghhwgmx5f0p-bzip2-1.0.6.0.1-bin/bin /nix/store/l3pxayz2xc1ldvph48xw5if3mgv56242-gnumake-4.2.1/bin /nix/store/yal9lwykvrf5mk1n608zx18yf69q776c-bash-4.4-p23/bin /nix/store/4wgaaplq0xpyf4kmd004ab1rjj2gilhb-patch-2.7.6/bin /nix/store/iifp7mfwymq5aa24nj0vm1vp4nzlh83z-xz-5.2.4-bin/bin /nix/var/nix/profiles/default/bin ~/.nix-profile/bin /run/current-system/sw/bin /usr/local/bin /usr/bin /bin /usr/sbin /sbin /Library/TeX/texbin

with empty shell.nix


In a lorri shell:
$ echo $PATH
/nix/store/2xv7ha3rsc8cd06hyajmhys91fnir3xg-clang-wrapper-7.1.0/bin /nix/store/adp1mzm4hwqnjff606xy4sf1vkjrb27m-clang-7.1.0/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/jd73bpkss4lcrkmyqv81vbvm5in9c31g-cctools-binutils-darwin-wrapper-927.0.2/bin /nix/store/3b45vydqz1id9592v1f4csgcrxhq3xpd-cctools-binutils-darwin-927.0.2/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/zgh5vpsdss3lmdqjv91d9hxsb1sm3qgb-clang-wrapper-9.0.1/bin /nix/store/2mida5726mrix1x8ma61103bm0z9c6vg-clang-9.0.1/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/jd73bpkss4lcrkmyqv81vbvm5in9c31g-cctools-binutils-darwin-wrapper-927.0.2/bin /nix/store/3b45vydqz1id9592v1f4csgcrxhq3xpd-cctools-binutils-darwin-927.0.2/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/qjg9jg0v757pklwix104vhz5kdcqfg3p-coreutils-8.31/bin /nix/store/nx9prqq9wpf555vlkc2wvblpnx9gjqph-findutils-4.7.0/bin /nix/store/c6m2442wbvcflsx33ybwf72c6sgr0460-diffutils-3.7/bin /nix/store/1lkinwnij0hdvmwfdxjcjb3wkcy3ysmh-gnused-4.8/bin /nix/store/y1wqnjcly40hpkwbfyd5pdinv8k5gyr8-gnugrep-3.4/bin /nix/store/s2gzkzg22m8jg0nbgza4jz0vbs77sgzp-gawk-5.0.1/bin /nix/store/s6hzqm5ma4jhif2gbc6slbw0a61rh99q-gnutar-1.32/bin /nix/store/0b7hgdzd8k72m10q76rrqfgscan7qgcv-gzip-1.10/bin /nix/store/d1p77cf3aq8frq903dhd1ghhwgmx5f0p-bzip2-1.0.6.0.1-bin/bin /nix/store/l3pxayz2xc1ldvph48xw5if3mgv56242-gnumake-4.2.1/bin /nix/store/yal9lwykvrf5mk1n608zx18yf69q776c-bash-4.4-p23/bin /nix/store/4wgaaplq0xpyf4kmd004ab1rjj2gilhb-patch-2.7.6/bin /nix/store/iifp7mfwymq5aa24nj0vm1vp4nzlh83z-xz-5.2.4-bin/bin /nix/var/nix/profiles/default/bin /Users/anrddh/.nix-profile/bin /run/current-system/sw/bin /usr/local/bin /usr/bin /bin /usr/sbin /sbin /Library/TeX/texbin .

with shell.nix:
let
  pkgs = import <nixpkgs> {};
in
pkgs.mkShell {
  buildInputs = [
    pkgs.clang_9
  ];
}