Execute a command at the start of every page

Question

Is there any way I can execute a command (\ifthenelse actually) at the start of every page?

I tried \AtBeginShipout (atbegshi) but that seem to get executed when the page is about to be rendered (shipped out). I want something different, as soon as the page is about to start.

Answer 1

You'll need the package bophook to add commands at the beginning of each page:

Using the \AtBeginPage hook, you can add material in the background of a page. Think of it as a construct that does: For every page, create a picture environment with its origin at the top left corner of the paper (resp., output device). So for example, you can put an image that is three centimeters from the left border and five from the top border by saying

\AtBeginPage{%
   \setlength{\unitlength}{1cm}
   \put(3, -5){\makebox(0,0)[tl]{\includegraphics{image}}}
}