Hi Ralph,

Ralph Corderoy wrote:
I've just used dd(1) to repeatedly read an SD card until it got all the
way through without an I/O error.  Quite a bit of the run time was
reading what had already been successfully read because I was lazy, or
had a better way to use my time.

It occurred to me that ddrescue(1) would do a better job, but I wouldn't
want a copy created in an output file.  I skimmed
https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html but
didn't see a way to do this, or a special meaning to an output file of

Thanks. I'll document this. As you suggest, /dev/null (combined with a mapfile) can be used to perform this task efficiently with a command like this one:

  ddrescue -f -r-1 /dev/sdcard /dev/null mapfile

A --scrub would be quite handy to read repeatedly until the media's
controller succeeds and re-maps the block internally.

The option '-r-1' (infinite retry passes) in the command above achieves exactly that.

Best regards,

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