History

Leonhard Kipp c42b588782 Refactor nu-cli/env* (#3041 ) * Revert "History, more test coverage improvements, and refactorings. (#3217)" This reverts commit `8fc8fc89aa`. * Add tests * Refactor .nu-env * Change logic of Config write to logic of read() * Fix reload always appends to old vars * Fix reload always takes last_modified of global config * Add reload_config in evaluation context * Reload config after writing to it in cfg set / cfg set_into * Add --no-history to cli options * Use --no-history in tests * Add comment about maybe_print_errors * Get ctrl_exit var from context.global_config * Use context.global_config in command "config" * Add Readme in engine how env vars are now handled * Update docs from autoenv command * Move history_path from engine to nu_data * Move load history out of if * No let before return * Add import for indexmap		2021-03-31 18:52:34 +13:00
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src	Refactor nu-cli/env* (#3041 )	2021-03-31 18:52:34 +13:00
tests	echo $scope.aliases \| pivot to see all of your aliases (#3203 )	2021-03-29 21:27:51 +13:00
Cargo.toml	Refactor nu-cli/env* (#3041 )	2021-03-31 18:52:34 +13:00
README.md	Refactor nu-cli/env* (#3041 )	2021-03-31 18:52:34 +13:00

README.md

Nu-Engine

Nu-engine handles most of the core logic of nushell. For example, engine handles: - Passing of data between commands - Evaluating a commands return values - Loading of user configurations

Top level introduction

The following topics shall give the reader a top level understanding how various topics are handled in nushell.

How are environment variables handled?

Environment variables (or short envs) are stored in the Scope of the EvaluationContext. That means that environment variables are scoped by default and we don't use std::env to store envs (but make exceptions where convenient).

Nushell handles environment variables and their lifetime the following:

At startup all existing environment variables are read and put into Scope. (Nushell reads existing environment variables platform independent by asking the Host. They will most likly come from std::env::*)
Envs can also be loaded from config files. Each loaded config produces a new ScopeFrame with the envs of the loaded config.
Nu-Script files and internal commands read and write env variables from / to the Scope. External scripts and binaries can't interact with the Scope. Therefore all env variables are read from the Scope and put into the external binaries environment-variables-memory area.