hexdump `_u` conversion outputs ambiguous string.

[agc]

Output hex codes for 12 and 255, then convert it to binary, and dump these using hexdump's '_u' conversion string, (_u means output US ASCII characters):

    printf '%.2x\n' 12 255 | xxd -r -p | hexdump -v -e '/1 " _%_u\_\n"'

Output:

     _ff_
     _ff_

Expected result would be two different strings, (maybe "FF" for the first one?), or failing that, to document this ambiguity in 'man hexdump'.

Note that some format strings like '_p' are quite non-specific, and output all non-printing chars as a '.', and that's to be expected. But for '_u' this is not expected, and the above is the only instance of ambiguous output, as shown by:

    printf '%.2x\n' {0..255} | xxd -r -p | \
    hexdump -v -e '/1 " _%_u\_\n"' | \
    sort | uniq -c | sort -nr | head -2

Output (i.e. the only duplicate is 'ff'):

      2 _ff_
      1 _Z_

Hope this helps...