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Last active December 14, 2015 02:49
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Demonstration of how gzip seems to embed a timestamp
> echo 'Hello!' > hello.txt
> # Create 2 tarballs at right about the same time:
> tar czf hello1.tar.gz hello.txt; tar czf hello2.tar.gz hello.txt
> md5 * # The tarballs have the same md5
MD5 (hello.txt) = e134ced312b3511d88943d57ccd70c83
MD5 (hello1.tar.gz) = bfdacca1166009500d60151d73c4da7e
MD5 (hello2.tar.gz) = bfdacca1166009500d60151d73c4da7e
> tar czf hello1.tar.gz hello.txt; tar czf hello2.tar.gz hello.txt
> md5 * # The tarballs have a different md5
MD5 (hello.txt) = e134ced312b3511d88943d57ccd70c83
MD5 (hello1.tar.gz) = b24c11090c4d49d58a1a1860460fced6
MD5 (hello2.tar.gz) = b24c11090c4d49d58a1a1860460fced6
> tar czf hello1.tar.gz hello.txt; sleep 1; tar czf hello2.tar.gz hello.txt
> md5 * # The tarballs have different md5s when created 1 second apart
MD5 (hello.txt) = e134ced312b3511d88943d57ccd70c83
MD5 (hello1.tar.gz) = 0b079bfb2f135c57c565c4e69ca6fbb3
MD5 (hello2.tar.gz) = 893adf011b8191a35b91b166c94e9d7e
> tar cf hello1.tar hello.txt; sleep 1; tar cf hello2.tar hello.txt
> md5 *.tar # The tar files have the same md5sum despite being created a second apart
MD5 (hello1.tar) = 08184f46132e863d0255fbf784fcaf2b
MD5 (hello2.tar) = 08184f46132e863d0255fbf784fcaf2b
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