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 repl-flake' nixpkgs
    Loading Installable 'flake:nixpkgs#'...
    Added 5 variables.
    
    nix-repl> legacyPackages.x86_64-linux.emacs.name
    "emacs-27.1"
    
    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

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.

  • --debugger

    Start an interactive environment if evaluation fails.

  • --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.

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. This option is deprecated; use --no-use-registries.

  • --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.

  • --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.

  • --update-input input-path

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

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.

  • --version

    Show version information.

Options that change the interpretation of installables:

  • --derivation

    Operate on the store derivation rather than its outputs.

  • --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.

Options to override configuration settings:

  • --accept-flake-config

    Enable the accept-flake-config setting.

  • --access-tokens value

    Set the access-tokens setting.

  • --allow-dirty

    Enable the allow-dirty setting.

  • --allow-import-from-derivation

    Enable the allow-import-from-derivation setting.

  • --allow-new-privileges

    Enable the allow-new-privileges setting.

  • --allow-symlinked-store

    Enable the allow-symlinked-store setting.

  • --allow-unsafe-native-code-during-evaluation

    Enable the allow-unsafe-native-code-during-evaluation setting.

  • --allowed-impure-host-deps value

    Set the allowed-impure-host-deps setting.

  • --allowed-uris value

    Set the allowed-uris setting.

  • --allowed-users value

    Set the allowed-users setting.

  • --auto-allocate-uids

    Enable the auto-allocate-uids setting.

  • --auto-optimise-store

    Enable the auto-optimise-store setting.

  • --bash-prompt value

    Set the bash-prompt setting.

  • --bash-prompt-prefix value

    Set the bash-prompt-prefix setting.

  • --bash-prompt-suffix value

    Set the bash-prompt-suffix setting.

  • --build-hook value

    Set the build-hook setting.

  • --build-poll-interval value

    Set the build-poll-interval setting.

  • --build-users-group value

    Set the build-users-group setting.

  • --builders value

    Set the builders setting.

  • --builders-use-substitutes

    Enable the builders-use-substitutes setting.

  • --commit-lockfile-summary value

    Set the commit-lockfile-summary setting.

  • --compress-build-log

    Enable the compress-build-log setting.

  • --connect-timeout value

    Set the connect-timeout setting.

  • --cores value

    Set the cores setting.

  • --diff-hook value

    Set the diff-hook setting.

  • --download-attempts value

    Set the download-attempts setting.

  • --download-speed value

    Set the download-speed setting.

  • --enforce-determinism

    Enable the enforce-determinism setting.

  • --eval-cache

    Enable the eval-cache setting.

  • --experimental-features value

    Set the experimental-features setting.

  • --extra-access-tokens value

    Append to the access-tokens setting.

  • --extra-allowed-impure-host-deps value

    Append to the allowed-impure-host-deps setting.

  • --extra-allowed-uris value

    Append to the allowed-uris setting.

  • --extra-allowed-users value

    Append to the allowed-users setting.

  • --extra-experimental-features value

    Append to the experimental-features setting.

  • --extra-extra-platforms value

    Append to the extra-platforms setting.

  • --extra-hashed-mirrors value

    Append to the hashed-mirrors setting.

  • --extra-ignored-acls value

    Append to the ignored-acls setting.

  • --extra-nix-path value

    Append to the nix-path setting.

  • --extra-platforms value

    Set the extra-platforms setting.

  • --extra-plugin-files value

    Append to the plugin-files setting.

  • --extra-sandbox-paths value

    Append to the sandbox-paths setting.

  • --extra-secret-key-files value

    Append to the secret-key-files setting.

  • --extra-substituters value

    Append to the substituters setting.

  • --extra-system-features value

    Append to the system-features setting.

  • --extra-trusted-public-keys value

    Append to the trusted-public-keys setting.

  • --extra-trusted-substituters value

    Append to the trusted-substituters setting.

  • --extra-trusted-users value

    Append to the trusted-users setting.

  • --fallback

    Enable the fallback setting.

  • --filter-syscalls

    Enable the filter-syscalls setting.

  • --flake-registry value

    Set the flake-registry setting.

  • --fsync-metadata

    Enable the fsync-metadata setting.

  • --gc-reserved-space value

    Set the gc-reserved-space setting.

  • --hashed-mirrors value

    Set the hashed-mirrors setting.

  • --http-connections value

    Set the http-connections setting.

  • --http2

    Enable the http2 setting.

  • --id-count value

    Set the id-count setting.

  • --ignore-try

    Enable the ignore-try setting.

  • --ignored-acls value

    Set the ignored-acls setting.

  • --impersonate-linux-26

    Enable the impersonate-linux-26 setting.

  • --keep-build-log

    Enable the keep-build-log setting.

  • --keep-derivations

    Enable the keep-derivations setting.

  • --keep-env-derivations

    Enable the keep-env-derivations setting.

  • --keep-failed

    Enable the keep-failed setting.

  • --keep-going

    Enable the keep-going setting.

  • --keep-outputs

    Enable the keep-outputs setting.

  • --log-lines value

    Set the log-lines setting.

  • --max-build-log-size value

    Set the max-build-log-size setting.

  • --max-free value

    Set the max-free setting.

  • --max-jobs value

    Set the max-jobs setting.

  • --max-silent-time value

    Set the max-silent-time setting.

  • --min-free value

    Set the min-free setting.

  • --min-free-check-interval value

    Set the min-free-check-interval setting.

  • --nar-buffer-size value

    Set the nar-buffer-size setting.

  • --narinfo-cache-negative-ttl value

    Set the narinfo-cache-negative-ttl setting.

  • --narinfo-cache-positive-ttl value

    Set the narinfo-cache-positive-ttl setting.

  • --netrc-file value

    Set the netrc-file setting.

  • --nix-path value

    Set the nix-path setting.

  • --no-accept-flake-config

    Disable the accept-flake-config setting.

  • --no-allow-dirty

    Disable the allow-dirty setting.

  • --no-allow-import-from-derivation

    Disable the allow-import-from-derivation setting.

  • --no-allow-new-privileges

    Disable the allow-new-privileges setting.

  • --no-allow-symlinked-store

    Disable the allow-symlinked-store setting.

  • --no-allow-unsafe-native-code-during-evaluation

    Disable the allow-unsafe-native-code-during-evaluation setting.

  • --no-auto-allocate-uids

    Disable the auto-allocate-uids setting.

  • --no-auto-optimise-store

    Disable the auto-optimise-store setting.

  • --no-builders-use-substitutes

    Disable the builders-use-substitutes setting.

  • --no-compress-build-log

    Disable the compress-build-log setting.

  • --no-enforce-determinism

    Disable the enforce-determinism setting.

  • --no-eval-cache

    Disable the eval-cache setting.

  • --no-fallback

    Disable the fallback setting.

  • --no-filter-syscalls

    Disable the filter-syscalls setting.

  • --no-fsync-metadata

    Disable the fsync-metadata setting.

  • --no-http2

    Disable the http2 setting.

  • --no-ignore-try

    Disable the ignore-try setting.

  • --no-impersonate-linux-26

    Disable the impersonate-linux-26 setting.

  • --no-keep-build-log

    Disable the keep-build-log setting.

  • --no-keep-derivations

    Disable the keep-derivations setting.

  • --no-keep-env-derivations

    Disable the keep-env-derivations setting.

  • --no-keep-failed

    Disable the keep-failed setting.

  • --no-keep-going

    Disable the keep-going setting.

  • --no-keep-outputs

    Disable the keep-outputs setting.

  • --no-preallocate-contents

    Disable the preallocate-contents setting.

  • --no-print-missing

    Disable the print-missing setting.

  • --no-pure-eval

    Disable the pure-eval setting.

  • --no-require-sigs

    Disable the require-sigs setting.

  • --no-restrict-eval

    Disable the restrict-eval setting.

  • --no-run-diff-hook

    Disable the run-diff-hook setting.

  • --no-sandbox

    Disable sandboxing.

  • --no-sandbox-fallback

    Disable the sandbox-fallback setting.

  • --no-show-trace

    Disable the show-trace setting.

  • --no-substitute

    Disable the substitute setting.

  • --no-sync-before-registering

    Disable the sync-before-registering setting.

  • --no-trace-function-calls

    Disable the trace-function-calls setting.

  • --no-trace-verbose

    Disable the trace-verbose setting.

  • --no-use-case-hack

    Disable the use-case-hack setting.

  • --no-use-cgroups

    Disable the use-cgroups setting.

  • --no-use-registries

    Disable the use-registries setting.

  • --no-use-sqlite-wal

    Disable the use-sqlite-wal setting.

  • --no-warn-dirty

    Disable the warn-dirty setting.

  • --plugin-files value

    Set the plugin-files setting.

  • --post-build-hook value

    Set the post-build-hook setting.

  • --pre-build-hook value

    Set the pre-build-hook setting.

  • --preallocate-contents

    Enable the preallocate-contents setting.

  • --print-missing

    Enable the print-missing setting.

  • --pure-eval

    Enable the pure-eval setting.

  • --relaxed-sandbox

    Enable sandboxing, but allow builds to disable it.

  • --repeat value

    Set the repeat setting.

  • --require-sigs

    Enable the require-sigs setting.

  • --restrict-eval

    Enable the restrict-eval setting.

  • --run-diff-hook

    Enable the run-diff-hook setting.

  • --sandbox

    Enable sandboxing.

  • --sandbox-build-dir value

    Set the sandbox-build-dir setting.

  • --sandbox-dev-shm-size value

    Set the sandbox-dev-shm-size setting.

  • --sandbox-fallback

    Enable the sandbox-fallback setting.

  • --sandbox-paths value

    Set the sandbox-paths setting.

  • --secret-key-files value

    Set the secret-key-files setting.

  • --show-trace

    Enable the show-trace setting.

  • --stalled-download-timeout value

    Set the stalled-download-timeout setting.

  • --start-id value

    Set the start-id setting.

  • --store value

    Set the store setting.

  • --substitute

    Enable the substitute setting.

  • --substituters value

    Set the substituters setting.

  • --sync-before-registering

    Enable the sync-before-registering setting.

  • --system value

    Set the system setting.

  • --system-features value

    Set the system-features setting.

  • --tarball-ttl value

    Set the tarball-ttl setting.

  • --timeout value

    Set the timeout setting.

  • --trace-function-calls

    Enable the trace-function-calls setting.

  • --trace-verbose

    Enable the trace-verbose setting.

  • --trusted-public-keys value

    Set the trusted-public-keys setting.

  • --trusted-substituters value

    Set the trusted-substituters setting.

  • --trusted-users value

    Set the trusted-users setting.

  • --use-case-hack

    Enable the use-case-hack setting.

  • --use-cgroups

    Enable the use-cgroups setting.

  • --use-registries

    Enable the use-registries setting.

  • --use-sqlite-wal

    Enable the use-sqlite-wal setting.

  • --user-agent-suffix value

    Set the user-agent-suffix setting.

  • --warn-dirty

    Enable the warn-dirty setting.