Equilibrium properties of inhomogeneous one-dimensional square-well fluids and their binary mixtures have been obtained exactly. Using the Laplace-transform technique for the evaluation of partition functions of one-dimensional systems with nearest-neighbour interactions, the canonical isobaric-isothermal and grand partition functions are determined. The molecular density distribution functions are determined from the grand partition function. The influence of nearest-neighbour interactions upon these functions is assessed. These systems can serve as simple models for describing selective adsorption of fluids in porous solids, and sample results are presented that show how molecular-size differences and attractive interactions determine selective adsorption.