env — environment variables

Source

lib/env.low

Layer

L2 — host (wrapper over a builtin op)

Capabilities

cap env

Environment variables are a channel that changes behaviour quietly from outside the program. Reading one therefore takes cap env, and that fact shows in the head of the op (chapter 16). The module is one wrapper that passes the builtin op env_get through.

use env .

proc has_home input e cap env . output bool . effects none . do
  let v option slice u8 env.get e. "HOME" . .
  return is_some v. . .
end .

op	shape	notes
env_get	(cap env, name slice u8) → option slice u8	The value of the variable with that name. none when it is not set

Table 50.1 — The ops of env

Not built: setting or removing a variable, listing all of them.