Notifications are very useful within macOS. The terminal, shell, does not provide a solution for triggering notitications. Being notified by a notification at the end of a long running command/script could save some time.

Without installing any other applications, the best way I found is using some AppleScript as a shell function.

Just add the following function to your .bashrc or .zshrc:

function _sys_notify() {
    local notification_command="display notification \"$2\" with title \"$1\" sound name \"Sonumi\""
    osascript -e "$notification_command"
}

alias sys-notify="_sys_notify $1 $2"

Triggering a notification:

$ sys-notify "My Nice Title" "With a longer message"

Bonus: A nice Sonumi sound is played.

Here is the result:

Notification triggered

Reference: The Apple documentation