kmerPrefixCounter seems to run without error, but writes an empty output file. >kmerPrefixCounter -i test.int -k 20 -o test-1 -l 1 -f 0 ... Mems_allowed_list: 0-1 voluntary_ctxt_switches: 5 nonvoluntary_ctxt_switches: 335 kmer_ct: 364633 compute time: 10.5024 write_time: 0.167927 SUCCESS! >ls -l -rw-r--r--. 1 user group 0 Aug 28 10:43 test.0 The test.int file has 77 nucleotide sequences. Headers are NCBI Taxonomy IDs (">10253", ">126794", etc.).