Section 5.3.7.1.2.4.  cifdiff

cifdiff is a C-shell script that takes two CIFs and lists the differences between them. Unlike the standard Unix utility diff, which compares files line-by-line, cifdiff can determine differences that are independent of reordering and white-space padding.

This script takes each CIF, converts it to a ZINC-format file, then sorts it, first based on the data-block name, then (keeping the loops together) on the data name. It then removes the last field (which is not part of the CIF) and stores the remainder in temporary files. It then runs the standard diff program against these reordered temporary files. This is remarkably effective both in finding any differences and in providing the context (it names the block and data name as well as the value) needed to understand the differences.

Fig. 5.3.7.2 illustrates two CIFs that are very different in the presentation of their contents, but have only a small difference of substance in their content. Fig. 5.3.7.3 indicates the output from cifdiff that identifies the changed data.

Figure 5.3.7.2 | top | pdf | Two example files in CIF format differing greatly in layout but little in content: (a) sample1.cif, (b) sample2.cif.

Figure 5.3.7.3 | top | pdf | Output from cifdiff comparing files sample1.cif and sample2.cif of Fig. 5.3.7.2. The entries in each line comprise the data-block name, the variable name, the zero-based index of the occurrence of the value in a looped list and the value. Hence it is the third value of _y in the loop that has changed.