Turn off Sleep and Screen Saver

Question

I am trying to write my first apples script that will set my computer and display sleep and screensaver interval to "never" when I connect an external display. This is what I have so far:
tell application "System Preferences"
launch
set current pane to pane id "com.apple.preference.energysaver"
tell application "System Events"
set value of every slider of tab group 1 of window "Energy Saver" of process "System Preferences" to 50
end tell
set current pane to pane id "com.apple.preference.desktopscreeneffect"
do shell script "defaults -currentHost write com.apple.screensaver idleTime 0"
quit
end tell
The sliders in Energy Saver move, but reset when I open system preferences to check them. The screen saver interval will not change. Why can I not change its interval in the same way as the other two sliders? Any help is greatly appreciated.

Answer 1

I wonder if it's possible to use GUI scripting to change those system preferences that require administrator privileges. Maybe that's the reason why the settings of the Energy Saver window were not saved after you moved the sliders. However you should be able to set the computer sleep time and the display sleep time with the following line of code:
do shell script "pmset -a sleep 3 displaysleep 3" user name "yourusername" password "your_password" with administrator privileges
On the other hand, using GUI Scripting, it should be possible to change the settings of the Desktop & Screen Saver window, since its preferences don't require administrator privileges:
tell application "System Preferences"
activate
delay 1
tell application "System Events"
tell process "System Preferences"
click menu item "Desktop & Screen Saver" of menu 1 of menu bar item "View" of menu bar 1
-- delay 1
set value of value indicator 1 of slider 1 of group 1 of tab group 1 of window "Desktop & Screen Saver" to 360
end tell
end tell
end tell
However, the value of the slider is not saved either when you quit the System Preferences. I don't know why.