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56 lines
2.1 KiB
Text
56 lines
2.1 KiB
Text
= The Nix REPL
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The Nix REPL (REPL is an acronym for Read-Eval-Print-Loop)
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is an interactive environment for evaluating and debugging Nix code.
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It's also a good place to begin learning Nix.
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Enter it using the command `nix repl`.
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Within the REPL, type `:?` to see a list of available commands.
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[source]
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....
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$ nix repl
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Welcome to Nix 2.18.1. Type :? for help.
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nix-repl> :?
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The following commands are available:
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<expr> Evaluate and print expression
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<x> = <expr> Bind expression to variable
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:a, :add <expr> Add attributes from resulting set to scope
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:b <expr> Build a derivation
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:bl <expr> Build a derivation, creating GC roots in the
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working directory
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:e, :edit <expr> Open package or function in $EDITOR
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:i <expr> Build derivation, then install result into
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current profile
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:l, :load <path> Load Nix expression and add it to scope
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:lf, :load-flake <ref> Load Nix flake and add it to scope
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:p, :print <expr> Evaluate and print expression recursively
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:q, :quit Exit nix-repl
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:r, :reload Reload all files
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:sh <expr> Build dependencies of derivation, then start
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nix-shell
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:t <expr> Describe result of evaluation
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:u <expr> Build derivation, then start nix-shell
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:doc <expr> Show documentation of a builtin function
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:log <expr> Show logs for a derivation
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:te, :trace-enable [bool] Enable, disable or toggle showing traces for
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errors
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:?, :help Brings up this help menu
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....
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A command that is useful to beginners is `:t`, which tells you the type of an expression.
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[source]
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.Example
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....
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nix-repl> :t { abc = true; "123" = false; }
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a set
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nix-repl> f = x: y: x * y
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nix-repl> :t f
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a function
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....
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Note that the command to exit the REPL is `:q` (or `:quit` if you prefer).
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