nix3-repl

Warning: This program is experimental and its interface is subject to change.

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 ‘readâevalâprint 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.