lush/issues/05-env-var-access.md

05 — Implement environment variable access (read/write)

Status: done Blocked by: #01

Add syntax for reading and writing environment variables directly from Lua.

Option 1 — export keyword

local var = "my data"
export var                    -- exports existing local to env
export other_var = "my data"  -- creates + exports

• New reserved word export in lexer
• export var looks up the local's value by name and calls setenv()
• export x = val combines declaration with setenv()

Option 2 — $ sigil

local dir = $PWD              -- getenv("PWD")
$PWD = "/"                    -- setenv("PWD", "/")
$MY_ENV_VAR = "data"          -- setenv("MY_ENV_VAR", "data")

• $NAME as expression → getenv("NAME"), returns string or nil
• $NAME = expr as statement → setenv("NAME", tostring(expr))
• New token type in lexer for $ + identifier

Implementation touches

• llex.c / llex.h — new token(s) or reserved word
• lparser.c — new expression/statement rules
• Runtime calls getenv() / setenv() — standard C, no shell needed
• Non-existent env var → return nil