On completion, dd shall write the number of input and output
blocks to standard error. In the POSIX locale the following
formats shall be used:
"%u+%u records in\n", <number of whole input blocks>,
<number of partial input blocks>
"%u+%u records out\n", <number of whole output blocks>,
<number of partial output blocks>
A partial input block is one for which read() returned less than
the input block size. A partial output block is one that was
written with fewer bytes than specified by the output block size.
In addition, when there is at least one truncated block, the
number of truncated blocks shall be written to standard error. In
the POSIX locale, the format shall be:
"%u truncated %s\n", <number of truncated blocks>, "record" (if
<number of truncated blocks> is one) "records" (otherwise)
Diagnostic messages may also be written to standard error.
