SG_DECODE_SENSE(8) SG3_UTILS SG_DECODE_SENSE(8)
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 decod-
ing is SPC-4 ANSI INCITS 513-2015 and the most recent draft SPC-5 revi-
sion 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 some-
thing 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 associ-
ated 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 hexa-
decimal 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 ar-
guments 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 an-
other 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 utili-
ties 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 in-
stead 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 sepa-
rated by space, comma, tab or newline. Everything from and in-
cluding 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 ex-
pected. 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 charac-
ters 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 represen-
tation of sense data (or anything else) into the equivalent bi-
nary 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. Other-
wise 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 war-
ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-
POSE.
SEE ALSO
sg_requests,sg_raw(sg3_utils)
sg3_utils-1.45 June 2019 SG_DECODE_SENSE(8)
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