How to transform GLSL shaders into ShaderLab shades?

Now I have severial GLSL shaders, and I want to use them in unity.Just put the GLSL code between #ifdef VERTEX .. #endif and #ifdef FRAGMENT .. #endif? (ps:I know little about GLSL, I don't want rewrite it in Cg)

But the manual say that using GLSL can limit my target platfrom. I want my game run on IOS and android. will this be a problem?

I have a feeling that it won't work well. Maybe at last I have to understand the logic in the GLSL shaders and rewrite them in Cg or HLSL.

Can anyone solve all my doubts.