NAME

       sg_decode_sense - decode SCSI sense and related data

SYNOPSIS

       sg_decode_sense  [--binary=FN]  [--cdb] [--err=ES] [--file=FN] [--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=FN
              the sense data is read in binary from a file called FN.

       -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=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. If --nospace is set then no separator is  required
              between  the  ASCII  hexadecimal  digits  in FN 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 FN 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 © 2010-2018 Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO warranty; not even for  MERCHANTABILITY
       or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

       sg_requests,sg_raw(sg3_utils)

sg3_utils-1.43                                     August 2018                                SG_DECODE_SENSE(8)