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# ---- System cron directories ----

# List scripts in each directory
ls /etc/cron.d/
ls /etc/cron.daily/
ls /etc/cron.weekly/
ls /etc/cron.monthly/
ls /etc/cron.hourly/

# Add a daily maintenance script
sudo cp /usr/local/bin/cleanup.sh /etc/cron.daily/cleanup
sudo chmod +x /etc/cron.daily/cleanup

# /etc/cron.d/ format (includes username field)
# cat /etc/cron.d/myapp:
# PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# 0 * * * * www-data /usr/local/bin/myapp_hourly.sh >> /var/log/myapp.log 2>&1

# /etc/crontab format (also includes username)
cat /etc/crontab

# ---- Logging cron output ----

# Good practice: always redirect in cron
# 30 2 * * * /usr/bin/backup.sh >> /var/log/backup.log 2>&1

# Timestamped logging in the script itself
log() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*"; }
# Then call: log "Backup started"

# View cron log entries
grep CRON /var/log/syslog
grep CRON /var/log/syslog | tail -50

# On systems with dedicated cron log
cat /var/log/cron     # RHEL/CentOS/Fedora

# ---- Test script in cron-like environment ----
# Simulate minimal cron environment
env -i HOME=/home/alice USER=alice \
    PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin \
    /bin/bash -c '/usr/local/bin/myscript.sh'

# Run a cron job manually to test
run-parts --test /etc/cron.daily
run-parts /etc/cron.daily      # Actually runs them