Name

       nix repl - start an interactive environment for evaluating Nix expressions

Synopsis

       nix repl [option…] files…

Examples

       • Display all special commands within the REPL:

       # nix repl
       nix-repl> :?

       • Evaluate some simple Nix expressions:

       # nix repl

       nix-repl> 1 + 2
       3

       nix-repl> map (x: x * 2) [1 2 3]
       [ 2 4 6 ]

       • Interact with Nixpkgs in the REPL:

       # nix repl '<nixpkgs>'

       Loading '<nixpkgs>'...
       Added 12428 variables.

       nix-repl> emacs.name
       "emacs-27.1"

       nix-repl> emacs.drvPath
       "/nix/store/lp0sjrhgg03y2n0l10n70rg0k7hhyz0l-emacs-27.1.drv"

       nix-repl> drv = runCommand "hello" { buildInputs = [ hello ]; } "hello; hello > $out"

       nix-repl> :b drv
       this derivation produced the following outputs:
       out -> /nix/store/0njwbgwmkwls0w5dv9mpc1pq5fj39q0l-hello

       nix-repl> builtins.readFile drv
       "Hello, world!\n"

       nix-repl> :log drv
       Hello, world!

Description

       This  command  provides  an  interactive environment for evaluating Nix expressions. (REPL
       stands for ‘read–eval–print loop’.)

       On startup, it loads the Nix expressions named files and adds them into the lexical scope.
       You can load addition files using the :l <filename> command, or reload all files using :r.

Options

       Common evaluation options:

       • --arg name expr
         Pass the value expr as the argument name to Nix functions.

       • --argstr name string
         Pass the string string as the argument name to Nix functions.

       • --eval-store store-url
         The Nix store to use for evaluations.

       • --impure
         Allow access to mutable paths and repositories.

       • --include / -I path
         Add path to the list of locations used to look up <...> file names.

       • --override-flake original-ref resolved-ref
         Override the flake registries, redirecting original-ref to resolved-ref.

                                                                                     nix3-repl(1)