---
title: "Clean up and exit with 128 plus the signal · Agent Wranglers"
url: https://agentwranglers.se/playbook/developer-tools/command-line-behaviour/signal-cleanup
id: DEV-13
level: Recommended
updated: 2026-10-27
build: a2a6bdfed830
tokens: 1117
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

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

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Command-line behaviour](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-27.

- ID: DEV-13
- Level: Recommended
- Chapter: [Command-line behaviour](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour.md)
- Rule: On SIGINT or SIGTERM, start no new work, delete temporary and lock files, restore the terminal and exit with 128 plus the signal number. A second Ctrl+C exits at once.
- 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.
- How: 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](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour/exit-codes.md). Long-running servers stop as [shut down without dropping requests](https://agentwranglers.se/playbook/operations/running-the-service/graceful-shutdown.md) says.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### Python example

```python
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

```go
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)
	}
}
```

## Sources

- [POSIX Shell Command Language, 2.8.2 Exit Status for Commands](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html)

## Related rules

- DEV-1 [Exit with zero only when the command did everything it was asked](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour/exit-codes.md) in Developer tools, SDKs and CLIs
- OPS-35 [Shut down cleanly](https://agentwranglers.se/playbook/operations/running-the-service/graceful-shutdown.md) in Operations and observability

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/developer-tools/command-line-behaviour/signal-cleanup">Agent Wranglers developer tools, SDKs and CLIs playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Make command-line tools read the locale or say they do not](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour/cli-locale.md)
- [Command-line behaviour](https://agentwranglers.se/playbook/developer-tools/command-line-behaviour.md)