Environment

Environment and exported variables

A variable's shell visibility and a declaration's module visibility are different. let export includes a binding in child-process environments. pub exports a symbol to importing Shelly modules.

let $local_note = "draft"
let export $SHELLY_WIKI_NOTE = "published"
let $bindings = get_env
echo $bindings["local_note"].value
echo $bindings["SHELLY_WIKI_NOTE"].visibility

draft
VariableVisibility::Exported

get_env returns [String: VariableInfo] for the visible scope, including shadowing. Keys and name omit the leading $. VariableInfo contains name, value, and a VariableVisibility (Local or Exported). These are snapshots of the binding information. optional_env reads an environment name and returns a String or ().

Retype an imported environment value

let type converts an existing binding and retains the conversion back to its original environment representation. The prelude supplies colon-separated String/array conversions, preserving empty entries.

let export $SHELLY_WIKI_PATH = "red::blue"
let type $SHELLY_WIKI_PATH = [String]
echo $SHELLY_WIKI_PATH.count
$SHELLY_WIKI_PATH = [$SHELLY_WIKI_PATH..., "green"]
/usr/bin/printenv SHELLY_WIKI_PATH

3
red::blue:green

This is useful for $PATH: work with [String] inside Shelly while children receive the conventional colon-separated text. Conversion uses target from_<source>, then source to_<target>, then built-in conversions.

Runtime variables

Variable	Purpose
$args	Script arguments.
$shelly	Current Shelly executable.
$pid	Current process ID.
$pwd	Current directory in user-facing path form.
$os	Platform name, such as linux or macos.
$tty_color_mode	Native TtyColorMode enum.
$SHELLY_MODULE_PATH	Search directories for ordinary imports.
$SHELLY_STD_PATH	Override standard-library search.
$SHELLY_STD_FOUND	Selected prelude root, embedded, or ().
$SHELLY_TAB_SIZE	Default source tab stops, from 1 through 32; defaults to 4.

A source's #tab-size N directive takes precedence over an explicit --tab-width N option, which takes precedence over $SHELLY_TAB_SIZE. Set the variable in a startup script to affect later submissions and module loads. Export it when child Shelly processes should inherit it. See pipeline splits.

Prompt, widget, history, and highlighting settings are described in their own chapters. Environment variable names are case sensitive.

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Related: Variables · Conversions · Startup