Usage: sg_test_rwbuf [--addrd=AR] [--addwr=AW] [--help] [--quick]
                     --size=SZ [--times=NUM] [--verbose] [--version]
                     DEVICE
 or
       sg_test_rwbuf DEVICE SZ [AW] [AR]
  where:
    --addrd=AR|-r    extra bytes to fetch during READ BUFFER
    --addwr=AW|-w    extra bytes to send to WRITE BUFFER
    --help|-l        output this usage message then exit
    --quick|-q       output read buffer size then exit
    --size=SZ|-s     size of buffer (in bytes) to write then read back
    --times=NUM|-t   number of times to run test (default 1)
    --verbose|-v     increase verbosity of output
    --version|-V     output version then exit

WARNING: If you access the device at the same time, e.g. because it's a
 mounted hard disk, the device's buffer may be used by the device itself
 for other data at the same time, and overwriting it may or may not
 cause data corruption!
(c) Douglas Gilbert, Kurt Garloff, 2000-2007, GNU GPL