File Watcher Skill for Claude

Configure file watching hooks to auto-react to config changes, env file updates, and dependency modifications. Use to set up reactive workflows.

602 tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

2755

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/rohitg00/pro-workflow --skill file-watcher

The instruction itself

10 sections, as written by the author

File Watcher

Use Claude Code's FileChanged and CwdChanged hooks to create reactive workflows that respond to file system changes.

Trigger

Use when:

Setting up auto-reload for config changes
Watching for dependency updates
Monitoring build output
Creating reactive development workflows

How File Watching Works

Claude Code's SessionStart and CwdChanged hooks support returning watchPaths to register file watchers. The current cwd-changed.js script focuses on env injection; to add watch registration, your hook script must output this JSON structure:

{
  "hookSpecificOutput": {
    "hookEventName": "SessionStart",
    "watchPaths": [
      "/absolute/path/to/.env",
      "/absolute/path/to/package.json"
    ]
  }
}

When watched files change, the FileChanged hook fires with:

{
  "hook_event_name": "FileChanged",
  "file_path": "/path/to/changed/file",
  "event": "change"
}

Environment Injection

CwdChanged and FileChanged hooks can write to CLAUDE_ENV_FILE to inject environment variables into subsequent Bash commands:

echo "export PROJECT_TYPE=node" >> "$CLAUDE_ENV_FILE"
echo "export TEST_CMD='npm test'" >> "$CLAUDE_ENV_FILE"

Common Watch Patterns

Watch .env for Changes

const envFile = path.join(projectRoot, '.env');
if (fs.existsSync(envFile)) {
  output.hookSpecificOutput = {
    hookEventName: 'SessionStart',
    watchPaths: [envFile]
  };
}

Watch package.json for Dependency Changes

Detect when dependencies change and remind to run npm install.

Watch tsconfig.json for Config Changes

Remind to restart TypeScript checks when config changes.

Setup

Add to hooks.json:

{
  "FileChanged": [{
    "matcher": ".env|package.json|tsconfig.json",
    "hooks": [{
      "type": "command",
      "command": "node scripts/file-changed.js"
    }]
  }]
}

Rules

Use absolute paths for watchPaths (required by Claude Code)
Matcher uses pipe-separated filenames
Watcher uses 500ms stability threshold and 200ms poll interval
Keep file-changed handlers fast (<5s) to avoid blocking
Use CLAUDE_ENV_FILE for injecting env vars, not direct export

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How to use it

Copy the folder

Take rohitg00/file-watcher from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.

Install what it needs

The instructions reference npm. Without those the skill loads but fails at the first command.