devenv-eval(1)

📦
version 2.4.0 · 2 versions
, in nixpkgs unstable

💖 devenv-eval(1) — the group chat edition 💖

okay so bestie, this is a page from the General Commands Manual, and it's about devenv-eval. grab a boba, we're getting into it 🧋✨

✨ NAME ✨

devenv-eval — evaluate, like, any attribute in devenv.nix and hand you back JSON. no cap. 💅

🦋 SYNOPSIS 🦋

devenv eval [--user-config] [--from] [-o|--override-input] [-O|--option]
[-j|--max-jobs] [-u|--cores] [-s|--system] [-i|--impure] [--no-impure]
[--offline] [--nix-option] [--nix-debugger] [-c|--clean] [-P|--profile]
[--reload] [--no-reload] [--shell] [--eval-cache] [--no-eval-cache]
[--refresh-eval-cache] [--refresh-task-cache] [--secretspec-provider]
[--secretspec-profile] [--trace-to] [-v|--verbose] [-q|--quiet] [--tui]
[--no-tui] [-h|--help] [ATTRIBUTES]

🌸 DESCRIPTION 🌸

Evaluate any attribute in devenv.nix and return JSON. that's it, that's the whole vibe — you point at a thing, it tells you what that thing is, in JSON. iconic. 👑

🎀 OPTIONS 🎀

  • --user-config <USER_CONFIG> — use this user configuration file instead of the XDG default. main character config file energy, fr fr. 🫶
  • [ATTRIBUTES] — the attribute(s) you wanna evaluate. yes bestie, this one's positional.

🌈 INPUT OVERRIDES 🌈

💜 --from <FROM>

Source for devenv.nix. it can be either a filesystem path (with the path: prefix, don't forget it!) or a flake input reference. lowkey my fave option ngl.

Examples, keep these exactly:

--from github:cachix/devenv
--from github:cachix/devenv?dir=examples/simple
--from path:/absolute/path/to/project
--from path:./relative/path

💜 -o, --override-input <NAME> <URI>

Override inputs in devenv.yaml. so clutch when you're pointing at your own fork 🍓

Examples:

--override-input nixpkgs github:NixOS/nixpkgs/nixos-unstable
--override-input nixpkgs path:/path/to/local/nixpkgs

💜 -O, --option <OPTION:TYPE> <VALUE>

Override configuration options with typed values. yes, you read that right, typed. we're being responsible today ✨

OPTION must include a type: <attribute>:<type>. Supported types are: string, int, float, bool, path, pkg, pkgs.

List types (pkgs) append to existing values by default. add a ! suffix to replace instead: pkgs!. the ! is doing so much work and honestly? slay.

Examples:

--option languages.rust.channel:string beta
--option services.postgres.enable:bool true
--option languages.python.version:string 3.10
--option packages:pkgs "ncdu git"       (appends to packages)
--option packages:pkgs! "ncdu git"      (replaces all packages)

🔥 NIX OPTIONS 🔥

⭐ -j, --max-jobs <MAX_JOBS>

Maximum number of Nix builds to run concurrently.

Defaults to 1/4 of available CPU cores (minimum 1). not me dividing your cores for you 😭

⭐ -u, --cores <CORES>

Number of CPU cores available to each build.

Defaults to available cores divided by max-jobs (minimum 1).

⭐ -s, --system <SYSTEM>

Override the target system.

Defaults to the host system (e.g. aarch64-darwin, x86_64-linux).

⭐ -i, --impure

Relax the hermeticity of the environment. letting a little chaos in, respectfully 🌪️

⭐ --no-impure

Force a hermetic environment, overriding config. back in the bubble bestie 🫧

⭐ --offline

Disable substituters and consider all previously downloaded files up-to-date. we're staying in tonight 💅

⭐ --nix-option <NAME> <VALUE>

Pass additional options to nix commands.

These options are passed directly to Nix using the --option flag. See man nix.conf for the full list of available options.

Examples:

--nix-option sandbox false
--nix-option keep-outputs true
--nix-option system x86_64-darwin

⭐ --nix-debugger

Enter the Nix debugger on failure. when things go sideways you get to go in there 😤

🐚 SHELL OPTIONS 🐚

🌸 -c, --clean [<CLEAN>...]

Ignore existing environment variables when entering the shell. pass a list of comma-separated environment variables to let through. fresh start, but like, on your terms ✨

🌸 -P, --profile <PROFILES>

Activate one or more profiles defined in devenv.nix.

Profiles allow you to define different configurations that can be merged with your base configuration.

See https://devenv.sh/profiles for more information.

Examples:

--profile python-3.14
--profile backend --profile fast-startup

🌸 --reload

Enable auto-reload when config files change (default). she's always listening 👀

🌸 --no-reload

Disable auto-reload when config files change. giving "do not disturb" mode 🎀

🌸 --shell <SHELL_TYPE>

Shell to use for interactive sessions (bash, zsh, fish, nu).

Possible values:

  • bash
  • zsh
  • fish
  • nu

💀 CACHE OPTIONS 💀

  • --eval-cache — enable caching of Nix evaluation results (default). we love a shortcut 🍓
  • --no-eval-cache — disable caching of Nix evaluation results.
  • --refresh-eval-cache — force a refresh of the Nix evaluation cache.
  • --refresh-task-cache — force a refresh of the task cache.

🙈 SECRETSPEC OPTIONS 🙈

  • --secretspec-provider <SECRETSPEC_PROVIDER> — override the secretspec provider. shh. 🤫
  • --secretspec-profile <SECRETSPEC_PROFILE> — override the secretspec profile.

🧚 TRACING OPTIONS 🧚

🦋 --trace-to <TRACE_TO>

Enable tracing and set output destination(s). can be repeated for multiple outputs. yes, repeated, stack 'em up 💅

Syntax: [format:]destination

Examples:

--trace-to stderr                              # json to stderr
--trace-to pretty:stderr                       # pretty format to stderr
--trace-to json:file:/tmp/trace.json           # JSON to file
--trace-to otlp-grpc                           # OTLP gRPC to default endpoint
--trace-to otlp-grpc:http://collector:4317     # OTLP gRPC to custom endpoint

Multiple outputs:

--trace-to pretty:stderr --trace-to json:file:/tmp/t.json

Destinations: stdout, stderr, file:<path>, http(s)://<host>:<port>

Formats: json (default), pretty, full, otlp-grpc, otlp-http-protobuf, otlp-http-json

When format is omitted, defaults to json. Tracing is disabled by default.

heads up bestie, these are the env vars: [env: DEVENV_TRACE_TO=] (comma-separated) and [env: DEVENV_TRACE_DEFAULT_TO=] (comma-separated, used only when no explicit tracing is configured; set to empty string to suppress). the empty-string-suppresses thing is important, don't sleep on it 🌙

👑 GLOBAL OPTIONS 👑

  • -v, --verbose — enable additional debug logs. she said "tell me everything" 🗣️
  • -q, --quiet — silence all logs. not a peep 🤐
  • --tui <TUI> — enable the interactive terminal interface (default when interactive).

Possible values:

  • true
  • false
  • --no-tui — disable the interactive terminal interface.
  • -h, --help — print help (see a summary with -h).
⚠️ real talk: -h gives you the summary, and full help is the longer version. the page said it, so i'm saying it 💖

and that's the whole page, bestie! 🎉 this one was from the General Commands Manual, the invocation is eval, and it's filed as devenv-eval(1). go evaluate something iconic. 💅✨🦋

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