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e2bitmap

e2bitmap is a quick hack I (pjm) wrote to satisfy my curiosity about what sort of cluster bitmaps most files have.

I include it in the main distribution because someone (Stefan Monnier) once asked for a program to do this.

The e2bitmap program tells you which clusters of a file are compressed, and which are uncompressed. The bitmap is represented as a list of ones and zeros, where `1' means a compressed cluster and `0' an uncompressed cluster, and the first cluster of the file is represented by the left-most digit.

If there are no compressed clusters then the word `uncompressed' is displayed instead of a list of digits.(4)

Another use for it is in cases where you want ext2fs to do only the online decompression while leaving the compression to a cron job (for instance). The cron job might use e2bitmap to see which files deserve recompression in order to avoid recompressing unchanged files over and over again. Use `chattr -m none files' to prevent the kernel from doing the compression right away, and, for example, `chattr -m gzip9 -s none files' in the cron job.

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