Expand description
std::process - process management: args, env, cwd, exec, exit, pid, sleep.
exec captures stdout and returns it as a string (trailing newline stripped).
exec_code returns only the exit code as int.
exec_lines returns stdout split into lines as arr[string].
Both args and cwd use with_raw_function since they take no rl arguments.
env returns null (not an error) when the variable is not set.