As covered in the previous recipe, the input variables within a vertex shader are linked to generic vertex attribute indices at the time the program is linked. If we need to specify the relationship, we can either use layout qualifiers within the shader, or we could call glBindAttribLocation before linking.

However, it may be preferable to let the linker create the mappings automatically and query for them after program linking is complete. In this recipe, we'll see a simple example that prints all the active attributes and their indices.