Cron and launchd

Two ways to schedule things

On Linux servers, cron is the historical scheduler. On macOS, Apple deprecated cron in favor of launchd — a service manager that doubles as a scheduler. Both are still around, but launchd is the recommended path on a Mac.

cron quick reference

crontab -e                 # edit your cron table
crontab -l                 # list it
*/5 * * * * /path/to/script.sh
0   3 * * 1 /path/to/weekly.sh

Five fields: minute hour day-of-month month day-of-week. cron runs as a stripped-down shell with a tiny PATH. Always set absolute paths and source what you need explicitly: 0 3 * * * . $HOME/.zshenv && /path/to/script.sh.

launchd LaunchAgent

Place a plist in ~/Library/LaunchAgents/. Load with launchctl bootstrap gui/$UID ~/Library/LaunchAgents/com.me.mytask.plist. Schedule via StartInterval (seconds) or StartCalendarInterval (cron-like dictionary). Survives reboot, supports auto-restart on crash.

<plist>
<dict>
  <key>Label</key>          <string>com.me.daily</string>
  <key>ProgramArguments</key> <array><string>/path/to/daily.sh</string></array>
  <key>StartCalendarInterval</key>
    <dict><key>Hour</key><integer>3</integer><key>Minute</key><integer>0</integer></dict>
  <key>StandardOutPath</key> <string>/tmp/daily.log</string>
</dict>
</plist>

Pippa note: APScheduler in-process

Pippa's heartbeat schedules don't use cron or launchd. They run inside pippa serve via APScheduler. launchd's only role is keeping pippa serve alive. The schedules themselves are in-process for ergonomics. So crontab -l on the office Mac is empty — that is by design.

When to use which

• Linux server → cron (or systemd timers).
• macOS → launchd LaunchAgent (user) or LaunchDaemon (root).
• App-internal schedules → embed a scheduler (APScheduler, node-cron) and let the OS keep your process alive. Often the cleanest path.