Setting Up Cron Jobs on macOS

Setting Up Cron Jobs on macOS | Generated by AI

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Question: How do you set up a crontab job on macOS?

Answer:

macOS uses cron just like Linux. The standard workflow:

# Open your crontab for editing (uses $EDITOR, default vi)
crontab -e

# List current crontab
crontab -l

# Remove all crontab entries
crontab -r

Crontab syntax:

# ┌─ minute (0-59)
# │ ┌─ hour (0-23)
# │ │ ┌─ day of month (1-31)
# │ │ │ ┌─ month (1-12)
# │ │ │ │ ┌─ day of week (0-7, 0 and 7 = Sunday)
# │ │ │ │ │
# * * * * *  command

Common examples:

# Every minute
* * * * * /usr/local/bin/python3 /Users/zhiwei/scripts/job.py

# Every 5 minutes
*/5 * * * * /path/to/script.sh

# Every day at 2am
0 2 * * * /path/to/backup.sh

# Every Monday at 9am
0 9 * * 1 /path/to/weekly.sh

# Every hour, log output
0 * * * * /path/to/script.sh >> /tmp/cron.log 2>&1

macOS-specific gotchas:

1. Full Disk Access for cron — macOS Catalina+ requires you to grant /usr/sbin/cron Full Disk Access in System Settings → Privacy & Security → Full Disk Access. Otherwise cron silently fails on file access.

2. PATH is minimal in cron — cron runs with a bare PATH=/usr/bin:/bin. Always use absolute paths:

# Bad
* * * * * python3 script.py

# Good
* * * * * /usr/bin/env python3 /Users/zhiwei/scripts/script.py

# Or set PATH explicitly at top of crontab
PATH=/usr/local/bin:/usr/bin:/bin
* * * * * python3 /Users/zhiwei/scripts/script.py

3. No shell expansion — ~ doesn’t work. Use full paths like /Users/zhiwei/.

4. Environment variables missing — your .zshrc, conda, pyenv, etc. are not sourced. If you depend on a venv:

* * * * * /Users/zhiwei/.venv/bin/python /Users/zhiwei/scripts/job.py

5. cron vs launchd — Apple prefers launchd (plist-based), but cron works fine for simple jobs. Only use launchd if you need:

Run on login/boot
Dependency management
Throttling/keepalive

Quick launchd equivalent for reference (daily at 2am):

<!-- ~/Library/LaunchAgents/com.zhiwei.myjob.plist -->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "...">
<plist version="1.0">
<dict>
  <key>Label</key><string>com.zhiwei.myjob</string>
  <key>ProgramArguments</key>
  <array>
    <string>/usr/bin/env</string>
    <string>python3</string>
    <string>/Users/zhiwei/scripts/job.py</string>
  </array>
  <key>StartCalendarInterval</key>
  <dict><key>Hour</key><integer>2</integer><key>Minute</key><integer>0</integer></dict>
  <key>StandardOutPath</key><string>/tmp/myjob.log</string>
  <key>StandardErrorPath</key><string>/tmp/myjob.err</string>
</dict>
</plist>

launchctl load ~/Library/LaunchAgents/com.zhiwei.myjob.plist
launchctl list | grep zhiwei  # verify

Debug cron not running:

# Check system log for cron errors
log show --predicate 'process == "cron"' --last 1h

# Or
grep cron /var/log/system.log 2>/dev/null || log show --last 30m | grep cron

For your use case (AI scripts, CLI agents, automation tools), cron with absolute venv paths is the fastest path. Reserve launchd for anything that needs to survive reboots or run at login.

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