Clean up and exit with 128 plus the signal number when stopped

How to do it

A tool stopped halfway leaves lock files that block the next run, temporary files that fill the disk and a terminal with no cursor. POSIX only says a command killed by a signal reports a status greater than 128. Shells such as bash report 128 plus the signal number, so callers expect 130 for SIGINT and 143 for SIGTERM. Write output to a temporary name and rename it only when the work is done, so an interrupted run never leaves half a file. Keep cleanup under 5 seconds. A person who presses Ctrl+C twice wants out now, so the second signal skips cleanup. The exit codes for other failures follow Exit with zero only when the command did everything it was asked. Long-running servers stop as shut down without dropping requests says.

Examples

Python example

import os, shutil, signal, sys, tempfile

SIGNAL_EXIT_BASE = 128
stopping = False

def on_signal(signum, _frame):
    global stopping
    if stopping:
        os._exit(SIGNAL_EXIT_BASE + signum)
    stopping = True
    raise SystemExit(SIGNAL_EXIT_BASE + signum)

signal.signal(signal.SIGINT, on_signal)
signal.signal(signal.SIGTERM, on_signal)

work_dir = tempfile.mkdtemp(prefix="example-")
try:
    run(work_dir)
finally:
    shutil.rmtree(work_dir, ignore_errors=True)
    sys.stderr.write("\x1b[?25h")

Go example

const signalExitBase = 128

func main() {
	workDir, err := os.MkdirTemp("", "example-")
	if err != nil {
		os.Exit(1)
	}
	signals := make(chan os.Signal, 2)
	signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
	ctx, cancel := context.WithCancel(context.Background())
	var received atomic.Int32
	go func() {
		first := (<-signals).(syscall.Signal)
		received.Store(int32(first))
		cancel()
		<-signals
		os.Exit(signalExitBase + int(first))
	}()
	runErr := run(ctx, workDir)
	os.RemoveAll(workDir)
	if sig := received.Load(); sig != 0 {
		os.Exit(signalExitBase + int(sig))
	}
	if runErr != nil {
		os.Exit(1)
	}
}

How to check

A test starts a long command and sends SIGINT after 1 second. The tool exits 130, and no temporary file, lock file or partial output file remains. SIGTERM gives 143. Two SIGINT signals 100 ms apart end the process within 1 second.

Sources

• POSIX Shell Command Language, 2.8.2 Exit Status for Commands

Related rules

• DEV-1 Exit with zero only when the command did everything it was asked in Developer tools, SDKs and CLIs
• OPS-35 Shut down cleanly in Operations and observability