There are 20K unique User-Agent strings in the logfile, which gives an extreme lower bound. $ cut -f12-100 -d' ' lpthw.Apr.04.2011.log | sed -e 's# "-"$##; s

There are 20K unique User-Agent strings in the logfile, which gives an extreme lower bound. $ cut -f12-100 -d' ' lpthw.Apr.04.2011.log | sed -e 's# "-"$##; s/^"//; s/"$//;' | \ sort | uniq -c | sed -e 's/^ *//' | \ sort -k1,1nr | tee ua.txt | wc -l 20122 UA is still far from uniquely identifying so this is a gross underestimate. If the IP field were hashed instead of 0.0.0.0 a better estimate would be possible, but the order of magnitude of the claim (100k) seems right to me.