For MacOS:

    #!/bin/bash
    # install in /usr/local/bin/nap
    if [ -z $1 ]; then
        echo "No time provided. Usage: nap [-cl] [minutes]"
        exit 2
    fi
    if [[ $1 == *c ]]; then
        echo Cancelling sleep. PIDs \(if any\): `pgrep -f "nap"`
        pkill -f "nap"
        exit 0
    fi
    if [[ $1 == *l ]]; then
        ps -Af | grep nap
        exit 0
    fi
    time=$(($1 * 60))
    echo Sleeping in $1 minutes...
    sleep $time && pmset sleepnow&

I wrote this 10+ years ago, still use it every day.