Which programs could be used to check the integrity of PDB files? And by that I mean recognize the (minimum) standard PDB format, check if there are missing residues (according to numbering in ATOM lines), missing atoms (according to residue identity and apart from hydrogens), non standard amino acids. I am pretty flexible for this task regarding programming languages, algorithms, personalization of runs, etc. I only need the programs to run in a Linux command line, provide an easy to parse output and be freely available for academic modification. However it would be interesting to make a point-by-point comparison if a big number of programs are available.