Prevent temporally suspend/hibernate from script?

To prvent hibernation, create /var/run/do-not-hibernate:

sudo touch /var/run/do-not-hibernate

The file /usr/lib/pm-utils/sleep.d/000kernel-change makes this work. If you need to disable suspend, create a new file for that, say /etc/pm/sleep.d/000_prevent_suspend_hibernate:

#!/bin/sh
# Prevents the machine from suspending or hibernating when
# the file /var/run/do-not-hibernate-or-suspend exist
case "$1" in
  suspend|hibernate)
    [ -f /var/run/do-not-hibernate-or-suspend ] && exit 1
    ;;
esac

Make it executable:

sudo chmod +x /etc/pm/sleep.d/000_prevent_suspend_hibernate

In case you need to prevent the machine from suspending or hibernating, create a file:

sudo touch /var/run/do-not-hibernate-or-suspend

After rebooting or removing this file, suspending and hibernating works again.