Man page - nix3-repl(1)

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Manual

nix3-repl

Name
Synopsis
Examples
Description
Options
Common evaluation options
Common flake-related options
Logging-related options
Miscellaneous global options
Options that change the interpretation of installables

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 …] installables …

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 --file example.nix
Loading Installable ’’...
Added 3 variables.

# nix repl --expr ’{a={b=3;c=4;};}’
Loading Installable ’’...
Added 1 variables.

# nix repl --expr ’{a={b=3;c=4;};}’ a
Loading Installable ’’...
Added 1 variables.

# nix repl --extra-experimental-features ’flakes’ nixpkgs
Loading Installable ’flake:nixpkgs#’...
Added 5 variables.

nix-repl> legacyPackages.x86_64-linux.emacs.name
"emacs-27.1"

nix-repl> :q

# nix repl --expr ’import <nixpkgs>{}’

Loading Installable ’’...
Added 12439 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

•

--stdin

Read installables from the standard input. No default installable applied.

Common evaluation options

•

--arg name expr

Pass the value expr as the argument name to Nix functions.

•

--arg-from-file name path

Pass the contents of file path as the argument name to Nix functions.

•

--arg-from-stdin name

Pass the contents of stdin as the argument name to Nix functions.

•

--argstr name string

Pass the string string as the argument name to Nix functions.

•

--debugger

Start an interactive environment if evaluation fails.

•

--eval-store store-url

The URL of the Nix store to use for evaluation, i.e. to store derivations (.drv files) and inputs referenced by them.

•

--impure

Allow access to mutable paths and repositories.

•

--include / -I path

Add path to search path entries used to resolve lookup paths

This option may be given multiple times.

Paths added through -I take precedence over the nix-path configuration setting and the NIX_PATH environment variable .

•

--override-flake original-ref resolved-ref

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

Common flake-related options

•

--commit-lock-file

Commit changes to the flake’s lock file.

•

--inputs-from flake-url

Use the inputs of the specified flake as registry entries.

•

--no-registries

Don’t allow lookups in the flake registries.

DEPRECATED

Use --no-use-registries instead.

•

--no-update-lock-file

Do not allow any updates to the flake’s lock file.

•

--no-write-lock-file

Do not write the flake’s newly generated lock file.

•

--output-lock-file flake-lock-path

Write the given lock file instead of flake.lock within the top-level flake.

•

--override-input input-path flake-url

Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.

•

--recreate-lock-file

Recreate the flake’s lock file from scratch.

DEPRECATED

Use nix flake update instead.

•

--reference-lock-file flake-lock-path

Read the given lock file instead of flake.lock within the top-level flake.

•

--update-input input-path

Update a specific flake input (ignoring its previous entry in the lock file).

DEPRECATED

Use nix flake update instead.

Logging-related options

•

--debug

Set the logging verbosity level to ‘debug’.

•

--log-format format

Set the format of log output; one of raw, internal-json, bar or bar-with-logs.

•

--print-build-logs / -L

Print full build logs on standard error.

•

--quiet

Decrease the logging verbosity level.

•

--verbose / -v

Increase the logging verbosity level.

Miscellaneous global options

•

--help

Show usage information.

•

--offline

Disable substituters and consider all previously downloaded files up-to-date.

•

--option name value

Set the Nix configuration setting name to value (overriding nix.conf).

•

--refresh

Consider all previously downloaded files out-of-date.

•

--repair

During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.

•

--version

Show version information.

Options that change the interpretation of installables

•

--expr expr

Interpret installables as attribute paths relative to the Nix expression expr .

•

--file / -f file

Interpret installables as attribute paths relative to the Nix expression stored in file . If file is the character -, then a Nix expression will be read from standard input. Implies --impure.

Note

See man nix.conf for overriding configuration settings with command line flags.