Ubuntu Manpage: sg_decode_sense - decode SCSI sense and related data

Provided by: sg3-utils_1.46-1build1_amd64

NAME

       sg_decode_sense - decode SCSI sense and related data

SYNOPSIS

       sg_decode_sense   [--binary=BFN]   [--cdb]   [--err=ES]   [--file=HFN]   [--help]  [--hex]
       [--nospace] [--status=SS] [--verbose] [--version] [--write=WFN] [H1 H2 H3 ...]

DESCRIPTION

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-4 ANSI INCITS 513-2015 and
the most recent draft SPC-5 revision 19 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 or
may be an informative warning. 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.

If the --cdb option is given then rather than viewing the given hex arguments as sense
data, it is viewed as a SCSI command descriptor block (CDB). In this case the command name
is printed out. That name is based on the first hex byte given (know as the opcode) and
optionally on another field called the "service action".

Another alternate action is when the --err=ES is given. ES is assumed to be an "exit
status" value between 0 and 255 from one of the utilities in this package. A descriptive
string is printed. Other options are ignored apart from --verbose.

OPTIONS

Arguments to long options are mandatory for short options as well.

-b, --binary=BFN
the sense data is read in binary from a file called BFN.

-c, --cdb
treat the given string of hex arguments as bytes in a SCSI CDB and decode the
command name.

-e, --err=ES
ES should be an "exit status" value between 0 and 255 that is available from the
shell (i.e. the utility's execution context) after the utility is finished. By
default an indicative error message is printed to stdout; and if the --verbose
option is given once (or an odd number of times) then the message is instead
printed to stderr. If --verbose is given two or more times a longer form of the
message is output. In all cases the message is less than 128 characters long with
one trailing line feed. All other command line options and arguments are ignored.

-f, --file=HFN
the sense data is read in ASCII hexadecimal from a file called HFN. 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. If
--nospace is set then no separator is required between the ASCII hexadecimal digits
in HFN with bytes decoded from pairs of ASCII hexadecimal digits.

-h, --help
output the usage message then exit.

-H, --hex
this option is used in conjunction with --write=WFN in order to change the output
written to WFN to lines of ASCII hex bytes suitable for a C language compiler. Each
line contains up to 16 bytes (e.g. a line starting with "0x3b,0x07,0x00,0xff").

-n, --nospace
expect ASCII hexadecimal to be a string of hexadecimal digits with no spaces
between them. Bytes are decoded by taking two hexadecimal digits at a time, so an
even number of digits is expected. The string of hexadecimal digits may be on the
command line (replacing "H1 H2 H3") or spread across multiple lines the HFN given
to --file=. On the command line, spaces (or other whitespace characters) between
sequences of hexadecimal digits are ignored; the maximum command line hex string is
1023 characters long.

-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 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. If the --hex
option is also given then ASCII hex is written to WFN (see the --hex option
description); otherwise binary is written to WFN. This option is a convenience and
may be helpful in converting the ASCII hexadecimal representation of sense data (or
anything else) into the equivalent binary or a compilable ASCII hex form.

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.

       The sg_raw utility takes a ASCII hexadecimal sequence representing a SCSI CDB. When sg_raw
       is given the '-vvv' option, it will attempt to decode the CDB name.

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:

       f0 00 03 00 00 12 34 0a  00 00 00 00 11 00 00 00
       00 00

       Cut and paste it after the sg_decode_sense command:

         sg_decode_sense f0 00 03 00 00 12 34 0a 00 00 00 00 11 00 00 00 00 00

       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.

AUTHORS

       Written by Douglas Gilbert.

REPORTING BUGS

       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

       Copyright © 2010-2019 Douglas Gilbert
       This  software  is distributed under a FreeBSD license. There is NO warranty; not even for
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.