fixcat.sh path-to-corrupted-catalog path-to-new-catalog.dat
As you will want to rebuild a catalog.dat file in the same location as the corrupted file, rename the corrupted file before running fixcat.
mv /myFiles/CATALOG.DAT /myFiles/CATALOG.DAT.bkup fixcat.sh /myFiles/CATALOG.DAT.bkup /myFiles/CATALOG.DAT