What does the trap-handler-generator produce?

A Bash pattern with a cleanup function, resource registry, error and signal handlers, and traps.

How are resources cleaned?

Resources are registered via register_cleanup and cleaned by the cleanup function, which removes dirs/files or runs commands.

Which traps are configured by default?

EXIT triggers cleanup, ERR triggers on_error, INT handles SIGINT, and TERM handles SIGTERM.

trap-handler-generator

npx machina-cli add skill a5c-ai/babysitter/trap-handler-generator --openclaw

Files (1)

SKILL.md

1.8 KB

Trap Handler Generator

Generate trap handlers for shell scripts.

Capabilities

Generate cleanup trap handlers
Implement signal handling
Create graceful shutdown logic
Set up resource cleanup
Handle nested traps
Generate error handlers

Generated Patterns

#!/usr/bin/env bash

# Temporary resources to clean up
declare -a CLEANUP_ITEMS=()
CLEANUP_DONE=false

# Register cleanup item
register_cleanup() {
    CLEANUP_ITEMS+=("$1")
}

# Cleanup function
cleanup() {
    if [[ "$CLEANUP_DONE" == true ]]; then
        return
    fi
    CLEANUP_DONE=true

    local exit_code=$?
    echo "Cleaning up..."

    for item in "${CLEANUP_ITEMS[@]}"; do
        if [[ -d "$item" ]]; then
            rm -rf "$item" 2>/dev/null
        elif [[ -f "$item" ]]; then
            rm -f "$item" 2>/dev/null
        elif [[ -n "$item" ]]; then
            # Command to run
            eval "$item" 2>/dev/null
        fi
    done

    return $exit_code
}

# Error handler
on_error() {
    local exit_code=$?
    local line_no=$1
    echo "Error on line ${line_no}: command exited with ${exit_code}" >&2
    cleanup
    exit $exit_code
}

# Signal handlers
on_sigint() {
    echo -e "\nInterrupted by user"
    cleanup
    exit 130
}

on_sigterm() {
    echo "Terminated"
    cleanup
    exit 143
}

# Set up traps
trap cleanup EXIT
trap 'on_error ${LINENO}' ERR
trap on_sigint INT
trap on_sigterm TERM

# Usage
TEMP_DIR=$(mktemp -d)
register_cleanup "$TEMP_DIR"

TEMP_FILE=$(mktemp)
register_cleanup "$TEMP_FILE"

register_cleanup "docker stop mycontainer"

Target Processes

shell-script-development
error-handling-user-feedback
cross-platform-cli-compatibility

Source

git clone https://github.com/a5c-ai/babysitter/blob/main/plugins/babysitter/skills/babysit/process/specializations/cli-mcp-development/skills/trap-handler-generator/SKILL.md

View on GitHub

Overview

Generates a reusable Bash pattern that automates cleanup, signal handling, and graceful shutdown in shell scripts. It defines a registry for cleanup items, a centralized cleanup function, error handling, and trap bindings to ensure resources are released on exit or error.

How This Skill Works

Outputs a Bash scaffold with a CLEANUP_ITEMS array, a register_cleanup function, and a cleanup function that loops over items to remove dirs/files or run commands. It also provides on_error, on_sigint, and on_sigterm handlers and wires them to EXIT, ERR, INT, and TERM traps.

When to Use It

Building long-running shell scripts that allocate temporary resources
Creating CLI tools that must clean up temp files on exit
Handling user interrupts (Ctrl+C) gracefully
Ensuring robust error reporting with cleanup on failures
Developing cross-platform shell scripts with consistent cleanup behavior

Quick Start

Step 1: Define CLEANUP_ITEMS and register_cleanup in your script
Step 2: Implement cleanup, on_error, on_sigint, on_sigterm, and traps
Step 3: Create resources with mktemp, register them, and test cleanup on exit

Best Practices

Register all resources with register_cleanup immediately after creation
Keep cleanup idempotent with a CLEANUP_DONE guard to prevent double runs
Use mktemp for temp dirs/files and register them for cleanup
Prefer cleanup-driven exits over ad-hoc termination logic
Test with ERR traps to verify cleanup paths and messages

Example Use Cases

Temp directory created with mktemp -d and registered for cleanup
Temp file created and registered for removal on exit
Registering a command like 'docker stop mycontainer' as a cleanup item
Error handler that logs the issue, runs cleanup, and exits with the original code
Signal handling for SIGINT and SIGTERM to trigger cleanup before exit

Frequently Asked Questions

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