Everyone knows that gzip’ing a file will usually make it smaller, but gzip’ing it again will not. In other words, once you’ve compressed a file, it won’t compress further. \u00a0 But here’s an exception.<\/p>\n
If you make a file of identical bytes, it can be gzip’ed several times and still become smaller. \u00a0In the example below, we made a 2GB file which consisted of identical bytes, all equal 0. \u00a0The first compression reduced the size by a factor of 1024. \u00a0The second by a factor of 602. \u00a0Next, by a factor of 14. \u00a0The next compression, not shown, grew the file by about 20 bytes. \u00a0The total compression, over the three generations, was a factor of 9,023,041\u00a0<\/strong>!<\/p>\n> dd if=\/dev\/zero of=2gb.zero bs=1024576 count=2048\n> gzip -c 2gb.zero > 2gb.zero.gz\n> gzip -c 2gb.zero.gz > 2gb.zero.gz.gz\n> gzip -c 2gb.zero.gz.gz > 2gb.zero.gz.gz.gz\n> ls -lh 2gb.zero\n2.0G\u00a0 2gb.zero\n2.0M\u00a0 2gb.zero.gz\n3.4K\u00a0 2gb.zero.gz.gz\n328B\u00a0 2gb.zero.gz.gz.gz<\/pre>\n","protected":false},"excerpt":{"rendered":"