I want to attached a second fragment shader to an OpenGL 1.2 shader program that gets its input from a fragment shader that writes to glFragColor. This is all implemented on FBO's with render-to-texture.

What is the correct syntax to access the RGBA pixel colors from the output of the first shader? The only variables I see in the orange book are glFrontColor and glBackColor, which I assume are for screen rendering, and not FBO rendering.prog

FYI- My first fragment shader accesses a 16 bit float texture from a film scan, so I don't want to lose the color precision.