$nix repl                                                                                                                                                             Welcome to Nix version 2.1.3. Type :? for help.

nix-repl> builtins.readFile /etc/os-release
"NAME=NixOS\nID=nixos\nVERSION=\"18.09.2466.884b0a4417e (Jellyfish)\"\nVERSION_CODENAME=jellyfish\nVERSION_ID=\"18.09.2466.884b0a4417e\"\nPRETTY_NAME=\"NixOS 18.09.2466.884b0a4417e (Jellyfish)\"\nHOME_URL=\"https://nixos.org/\"\nSUPPORT_URL=\"https://nixos.org/nixos/support.html\"\nBUG_REPORT_URL=\"https://github.com/NixOS/nixpkgs/issues\"\n"

nix-repl> builtins.readFile /proc/cpuinfo
""