dual-channel-watchexec-notifications

Dual-Channel Watchexec Notifications

Send reliable notifications to both Telegram and Pushover when watchexec detects file changes or process crashes.

Core Pattern

watchexec wrapper script → detect event → notify-script → Telegram + Pushover

# wrapper.sh - Monitors process and detects restart reasons
watchexec --restart -- python bot.py

# On event, call:
notify-script.sh <reason> <exit_code> <watchexec_info_file> <crash_context>

Critical Rule: Format Differences

Telegram: HTML mode ONLY

MESSAGE="<b>Alert</b>: <code>file.py</code>"
# Escape 3 chars: & → &amp;, < → &lt;, > → &gt;

Pushover: Plain text ONLY

/usr/bin/env bash << 'SKILL_SCRIPT_EOF'
# Strip HTML tags before sending
MESSAGE_PLAIN=$(echo "$MESSAGE_HTML" | sed 's/<[^>]*>//g')
SKILL_SCRIPT_EOF

Why HTML for Telegram:

• Markdown requires escaping 40+ chars (., -, _, etc.)
• HTML only requires escaping 3 chars (&, <, >)
• Industry best practice

Quick Reference

Send to Both Channels

/usr/bin/env bash << 'SKILL_SCRIPT_EOF_2'
# 1. Build HTML message for Telegram
MESSAGE_HTML="<b>File</b>: <code>handler_classes.py</code>"

# 2. Strip HTML for Pushover
MESSAGE_PLAIN=$(echo "$MESSAGE_HTML" | sed 's/<[^>]*>//g')

# 3. Send to Telegram with HTML
curl -s -d "chat_id=$CHAT_ID" \
  -d "text=$MESSAGE_HTML" \
  -d "parse_mode=HTML" \
  https://api.telegram.org/bot$BOT_TOKEN/sendMessage

# 4. Send to Pushover with plain text
curl -s --form-string "message=$MESSAGE_PLAIN" \
  https://api.pushover.net/1/messages.json
SKILL_SCRIPT_EOF_2

Execution Pattern

# Fire-and-forget background notifications (don't block restarts)
"$NOTIFY_SCRIPT" "crash" "$EXIT_CODE" "$INFO_FILE" "$CONTEXT_FILE" &

Validation Checklist

Before deploying:

• Using HTML parse mode for Telegram (not Markdown)
• HTML tags stripped for Pushover (plain text only)
• HTML escaping applied to all dynamic content (&, <, >)
• Credentials loaded from env vars/Doppler (not hardcoded)
• Message archiving enabled for debugging
• File detection uses stat (not find -newermt)
• Heredocs use unquoted delimiters for variable expansion
• Notifications run in background (fire-and-forget)
• Tested with files containing special chars (_, ., -)
• Both Telegram and Pushover successfully receiving

Summary

Key Lessons:

1. Always use HTML mode for Telegram (simpler escaping)
2. Always strip HTML tags for Pushover (plain text only)
3. Escape only 3 chars in HTML: & → &, < → <, > → >
4. Archive messages before sending for debugging
5. Use stat for file detection on macOS (not find -newermt)
6. Load credentials from env vars/Doppler (never hardcode)
7. Fire-and-forget background notifications (don't block restarts)

Reference Documentation

For detailed information, see:

• Telegram HTML - HTML mode formatting and message templates
• Pushover Integration - API calls and priority levels
• Credential Management - Doppler, env vars, and keychain patterns
• Watchexec Patterns - File detection and restart reason detection
• Common Pitfalls - HTML tags in Pushover, escaping issues, macOS compatibility

Bundled Examples:

• examples/notify-restart.sh - Complete dual-channel notification script
• examples/bot-wrapper.sh - watchexec wrapper with restart detection
• examples/setup-example.sh - Setup guide and installation steps