This is makeindex, version 2.15 [TeX Live 2022/dev] (kpathsea + Thai support).
Scanning input file refman.idx....done (348 entries accepted, 0 rejected).
Sorting entries......done (3176 comparisons).
Generating output file refman.ind....done (379 lines written, 0 warnings).
Output written in refman.ind.
Transcript written in refman.ilg.
