pub fn execute(args: &mut Vec<String>, flags: u32, defpath: i32)Port of static void execute(LinkList args, int flags, int defpath)
from Src/exec.c:723. The canonical “child runs the simple
external command” path: STTY/ARGV0/BINF_DASH handling, makecline,
closem(FDT_XTRACE) + child_unblock, slash-path direct exec,
defpath (command -p) search, cmdnamtab + $PATH walk, with
commandnotfound-handler fallback and the final exit-code escape
(127 not-found / 126 noperm).
cmdnamtab->getnode(cmdnamtab, arg0) (c:824) — HASHED
fast-path wired via cmdnamtab_lock(); jumps direct to
cn.cmd absolute path before the $PATH scan. Unhashed
cursor-walk (c:830-846) still falls to the full $PATH scan;
observable behavior matches C when the hash hit is HASHED.
(b) commandnotfound(arg0, args) (c:809, 873) calls into the
not-yet-ported doshfunc for the command_not_found_handler
shell function. Already routes through executor dispatch
(see exec.rs:2783).
(c) _realexit() (c:810, 874) — bare std::process::exit.
(d) SHTTY close on !FD_CLOEXEC (c:781-784) — Rust assumes
FD_CLOEXEC platform default (macOS, Linux).
(e) path Rust accessor uses paramtab lookup for “PATH”;
defpath (command -p) walks DEFAULT_PATH via
search_defpath (already ported).