On Wed, Jul 2, 2014 at 6:04 PM, Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote: > but it's just dangerous to assume that will be forever true Agreed with this, but: > and as you can see below with gzip you have *always* > different results for the same data This is not true, see below. > [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 1.tar.gz test.bin > [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 2.tar.gz test.bin > [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 3.tar.gz test.bin > [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 4.tar.gz test.bin > [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 5.tar.gz test.bin > [harry@srv-rhsoft:~/Desktop]$ md5sum *.gz > 8f132cafffe6d7a613a480a5e593abc8 1.tar.gz > 3cf402bbbde27db631a2896af9365275 2.tar.gz > 5cb1fc9f6628a41d71572862ea4c19a1 3.tar.gz > bd51a4779ca4e2e9377488dc64ccaf1c 4.tar.gz > 5506a0cfbf39cb28b05babba6755049a 5.tar.gz These tests are faulty, they're not testing gzip with the same data. You're (well tar is internally) gzipping five temporary tarballs that have different timestamps and/or filenames, and gzip's default behavior is to store original file's filename and timestamp so naturally they differ. To actually test gzip, do for example: $ gzip -c test.bin > 1.gz $ gzip -c test.bin > 2.gz $ md5sum *gz aca340cd42ffd3b2c6a25b646637cae5 1.gz aca340cd42ffd3b2c6a25b646637cae5 2.gz ...or if you want to do it with tar, need to tell it to pass -n to gzip, for example: $ tar c test.bin -I "gzip -n" > 1.tar.gz $ tar c test.bin -I "gzip -n" > 2.tar.gz $ md5sum *gz 03d30b886f9a2f5219909662586e44b5 1.tar.gz 03d30b886f9a2f5219909662586e44b5 2.tar.gz -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
