Comment by 0xEFF

The caffeinate command is built into macos.

Edit: This keeps the computer awake until 6 PM each day.

  caffeinate -u -i -s -t $(($(date -j -f "%a %b %d %T %Z %Y" "$(date +"%a %b %d 18:00:00 %Z %Y")" "+%s") - $(date +%s)))