This utility takes SCSI sense data in binary or as a sequence of
ASCII hexadecimal bytes and decodes it. The primary reference for the
decoding is SPC-3 ANSI INCITS 408-2005 and the most recent draft
SPC-4 revision 29 which can be found at http://www.t10.org and other
locations on the internet.
SCSI sense data is often found in kernel log files as a result of
something going wrong but may just be informative. It is often shown as
a sequence of hexadecimal bytes, starting with 70, 71, 72, 73, f0 or f1.
Sense data could be up to 252 bytes long but typically is much shorter
than that, 18 bytes long is often seen and is usually associated with
the older "fixed" format sense data.
The sense data can be provided on the command line or in a file. If
given on the command line the sense data should be a sequence of
hexadecimal bytes separated by space. Alternatively a file can be
given with the contents in binary or ASCII hexadecimal bytes. The
latter form can contain several lines each with none, one or more
ASCII hexadecimal bytes separated by space (comma or tab). The
hash symbol may appear and it and the rest of the line is ignored
making it useful for comments.
OPTIONS
Arguments to long options are mandatory for short options as well.
-b, --binary=FN
the sense data is read in binary from a file called FN.
-h, --help
output the usage message then exit.
-f, --file=FN
the sense data is read in ASCII hexadecimal from a file called FN.
The sense data should appear as a sequence of bytes separated by space,
comma, tab or newline. Everything from and including a hash symbol to the
end of that line is ignored.
-s, --status=SS
where SS is a SCSI status byte value, given in hexadecimal. The
SCSI status byte is related to but distinct from sense data.
-v, --verbose
increase the degree of verbosity (debug messages).
-V, --version
output version string then exit.
-w, --write=WFN
writes the sense data out in binary to a file called WFN. If
necessary WFN is created. If WFN exists then it is
truncated prior to writing the sense data to it. This option is
a convenience and may be helpful in converting the ASCII hexadecimal
representation of sense data into the equivalent binary.
NOTES
Unlike most utilities in this package, this utility does not access a
SCSI device (logical unit). This utility accesses a library associated
with this package. Amongst other things the library decodes SCSI sense
data.
EXAMPLES
Sense data is often printed out in kernel logs and sometimes on the
command line when verbose or debug flags are given. It will be at least
8 bytes long, often 18 bytes long but may be longer. A sense data string
might look like this:
and for this sense data the output should look like this:
Fixed format, current; Sense key: Medium Error
Additional sense: Unrecovered read error
Info fld=0x1234 [4660]
For a medium error the Info field is the logical block address (LBA)
of the lowest numbered block that the associated SCSI command was not
able to read (verify or write).
EXIT STATUS
The exit status of sg_decode_sense is 0 when it is successful. Otherwise
see the sg3_utils(8) man page.