On 05/22/2009 02:09 PM, Samuel Thibault wrote:
Hello,Since at least tar 1.22, there is an additional warning in short_read: if (left&& left % BLOCKSIZE == 0 && verbose_option && record_start_block == 0&& status != 0) { unsigned long rsize = status / BLOCKSIZE; WARN ((0, 0, ngettext ("Record size = %lu block", "Record size = %lu blocks", rsize), rsize)); } Why is that done? Reads on pipes typically return short reads, and these are typically aligned on page size, and thus record_size (10240 here) % BLOCKSIZE is typically 0...
It has been discussed before, for example at http://www.nabble.com/tar:-Record-size-%3D-8-blocks-td22265061.html and http://www.nabble.com/record-size-%3D-x-blocks--td22477515.html
The current behaviour was introduced because it sometimes provides useful information on tape / block devices. FWIW I still don't see how any kind of semantics in read chunk sizes can ever be reliable anywhere.
/Mads
