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1.0 of sparse format was introduced with GNU
1.15.92. Its main objective was to make the resulting file
extractable with little effort even by non-posix aware
implementations. Starting from this version, the extended header
preceding a sparse member always contains the following variables that
identify the format being used:
name field in
ustar header contains a special name,
constructed using the following pattern:
The real name of the sparse file is stored in the variable
GNU.sparse.name. The real size of the file is stored in the
The sparse map itself is stored in the file data block, preceding the actual file data. It consists of a series of octal numbers of arbitrary length, delimited by newlines. The map is padded with nulls to the nearest block boundary.
The first number gives the number of entries in the map. Following are map entries, each one consisting of two numbers giving the offset and size of the data block it describes.
The format is designed in such a way that non-posix aware
GNU.sparse.* keywords will extract each sparse file
in its condensed form with the file map prepended and will place it
into a separate directory. Then, using a simple program it would be
possible to expand the file to its original form even without GNU
See section Extracting Sparse Members, for the detailed information on how to extract
sparse members without GNU
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