Terms and Definitions in Nix Project

Terms and Definitions

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Term	Context	Meaning	Related Links
rec { }	Nix expressions	The { } block contains "mutually recursive" attributes, which means they can refer to each other.	Composing the Hello Package
expression evaluator	Nix	The part of the Nix program which reads and evaluates a Nix expression.	Nix Manual: Common Options --arg Nix Manual: Built-in Functions
Derivation	Nix	A Nix expression which describes a build action. When evaluated, it creates one or more entries in the Nix Store. The nix-instantiate command is the command which creates entries in the Nix Store, while the nix-env and nix-build commands are its user-friendly interface.	Nix Manual: Glossary -> Derivation Nix Manual: Derivation
stdenv	Nix expressions	An attribute which contains things expected in the most basic Unix environment. (e.g. Bash shell, gcc, cp, tar, grep, etc.)	all-packages.nix: stdenv =]
User Environment	Nix	A set of "active" applications. These applications often exist in the Nix store. A single Nix user may have multiple User Environments. This is an important concept further explored in User Environment. Profiles and generations are closely related.	Nix Manual - Basic Package Management chapter Nix Manual - Profiles chapter Nix Manual - nix-env
User Profile	Nix	A user's currently selected User Environment.	Nix Manual: Glossary
Generation	Nix	A past revision of a user's environment. This term connotes the cloning and modification of an existing user environment. Nix's environment rollback facilities rely on Generations.	Nix Manual: Profiles
config.nix or nixpkgs-config.nix	NixOS Wiki	A Nix expression retrieved by and applied to the all-packages.nix Nix expression. This file enables an end-user to customize the Nix expressions contained in the community-owned NixPkgs list or to define entirely new Nix expressions to use with Nix commands. This file's path can be overridden by the NIXPKGS_CONFIG environment variable.	all-packages.nix: config NixPkgs Release Notes
attribute path	nix-env takes this if you pass the `-A` flag [1]	an unambiguous identifier for a package
symbolic package name	[2]	This string represents what you commonly think of as a package. There can be multiple packages with the symbolic name "hello".
selector	this term is used in nix-env error messages [3], it seems to be actually a DrvName struct [4] (a derivation name)	see "symbolic package name"
selection path	nix-shell error message [5]	see "attribute path"[6]
derivation name	manual[7], source code [8]	see "symbolic package name"
package name	IRC[9]	see "symbolic package name"
attribute selection path	source[10]	see "attribute path"