Some kinds of bibliography files should be kept in a different order than alphabetically by citation labels. Good examples are a bibliography file with the contents of a journal, or a personal publication list, for both of which chronological publication order is likely to be preferred. While a much more sophisticated implementation of bibsort could deal with the first point, and the -byvolume switch provides a partial solution to the third point, in general, a satisfactory solution requires human intelligence and natural language understanding that computers lack. If any of these are already present in the input, they will be altered on output. This is unlikely to be a problem, because those characters have neither a printable representation, nor are they conventionally used to mark line or page boundaries in text files.
Some text editors permit application of an arbitrary filter command to a region of text.
The current implementation of bibsort follows the UNIX tradition of combining simple already-available tools. The initial prototype of bibsort was written and tested on several large bibliographies in a couple of hours, and after considerable use, was later extended with advanced sorting capabilities and cross-reference recognition in a couple of days of work. If a space is required, you must quote the pair, to prevent the nnnnn value from being interpreted as a filename by bibsort .