Shell

Run external programs, connect pipelines and capture their output from RecurLoop. Shell passes argument vectors to programs; it does not delegate each command to another shell.

Choose the right operation

Operation	Where to use it	Result
`run`	top level or a typed function	exit status
`capture`	top level or a typed function	standard output
`spawn`	inside a typed function	owned `Shell:Invocation*`
`Shell:Pipeline`	computed argument lists	owned pipeline object

recurloop

import shell
run printf "hello\n" | tr a-z A-Z
assert status == 0

The output is HELLO. At top level status is a runtime binding. Inside a typed function, assign the return value of run instead of reading that binding.

Do not free borrowed Invocation:stdout text. Do free the string returned by capture inside a typed function. The two APIs deliberately have different ownership.

Learning path

Commands — Quote arguments and select command syntax.
Pipelines — Connect streams and handle stage failures.
Capture and jobs — Collect output and inspect running invocations.
Command objects — Construct commands from runtime data.
Process settings — Scope process settings and coordinate parallel jobs.