Take object filenames (e.g., files with .o suffix) and output a list of related pairs. The first file listed includes references to external identifiers that are defined in the second. lorder output can be sent to tsort to make link editing of an archive more efficient.
To produce an ordered list of object files, and replace them in the library program_arch (provided they are newer):
ar cru program_arch `lorder *.o | tsort`