1SG_DECODE_SENSE(8)                 SG3_UTILS                SG_DECODE_SENSE(8)
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NAME

6       sg_decode_sense - decode SCSI sense and related data
7

SYNOPSIS

9       sg_decode_sense [--binary=BFN] [--cdb] [--err=ES] [--file=HFN] [--help]
10       [--hex] [--nospace] [--status=SS] [--verbose] [--version] [--write=WFN]
11       [H1 H2 H3 ...]
12

DESCRIPTION

14       This  utility takes SCSI sense data in binary or as a sequence of ASCII
15       hexadecimal bytes and decodes it. The primary reference for the  decod‐
16       ing is SPC-4 ANSI INCITS 513-2015 and the most recent draft SPC-5 revi‐
17       sion 19 which can be found at http://www.t10.org and other locations on
18       the internet.
19
20       SCSI sense data is often found in kernel log files as a result of some‐
21       thing going wrong or may be an informative warning. It is  often  shown
22       as a sequence of hexadecimal bytes, starting with 70, 71, 72, 73, f0 or
23       f1.  Sense data could be up to 252 bytes long  but  typically  is  much
24       shorter  than  that, 18 bytes long is often seen and is usually associ‐
25       ated with the older "fixed" format sense data.
26
27       The sense data can be provided on the command line or  in  a  file.  If
28       given  on the command line the sense data should be a sequence of hexa‐
29       decimal bytes separated by space. Alternatively a  file  can  be  given
30       with the contents in binary or ASCII hexadecimal bytes. The latter form
31       can contain several lines each with none, one or more ASCII hexadecimal
32       bytes separated by space (comma or tab). The hash symbol may appear and
33       it and the rest of the line is ignored making it useful for comments.
34
35       If the --cdb option is given then rather than  viewing  the  given  hex
36       arguments  as  sense  data,  it  is viewed as a SCSI command descriptor
37       block (CDB). In this case the command name is printed out. That name is
38       based  on  the first hex byte given (know as the opcode) and optionally
39       on another field called the "service action".
40
41       Another alternate action is when the --err=ES is given. ES  is  assumed
42       to  be  an "exit status" value between 0 and 255 from one of the utili‐
43       ties in this package. A descriptive string is  printed.  Other  options
44       are ignored apart from --verbose.
45

OPTIONS

47       Arguments to long options are mandatory for short options as well.
48
49       -b, --binary=BFN
50              the sense data is read in binary from a file called BFN.
51
52       -c, --cdb
53              treat  the  given string of hex arguments as bytes in a SCSI CDB
54              and decode the command name.
55
56       -e, --err=ES
57              ES should be an "exit status" value between 0 and  255  that  is
58              available  from the shell (i.e. the utility's execution context)
59              after the utility is finished. By default  an  indicative  error
60              message  is  printed  to  stdout; and if the --verbose option is
61              given once (or an odd number  of  times)  then  the  message  is
62              instead  printed  to  stderr.  If --verbose is given two or more
63              times a longer form of the message is output. In all  cases  the
64              message  is less than 128 characters long with one trailing line
65              feed. All other command line options and arguments are ignored.
66
67       -f, --file=HFN
68              the sense data is read in ASCII hexadecimal from a  file  called
69              HFN.   The sense data should appear as a sequence of bytes sepa‐
70              rated by space, comma,  tab  or  newline.  Everything  from  and
71              including  a  hash symbol to the end of that line is ignored. If
72              --nospace is set then no separator is required between the ASCII
73              hexadecimal digits in HFN with bytes decoded from pairs of ASCII
74              hexadecimal digits.
75
76       -h, --help
77              output the usage message then exit.
78
79       -H, --hex
80              this option is used in conjunction with --write=WFN in order  to
81              change  the  output  written  to WFN to lines of ASCII hex bytes
82              suitable for a C language compiler. Each line contains up to  16
83              bytes (e.g. a line starting with "0x3b,0x07,0x00,0xff").
84
85       -n, --nospace
86              expect  ASCII  hexadecimal  to be a string of hexadecimal digits
87              with no spaces between them. Bytes are  decoded  by  taking  two
88              hexadecimal  digits  at  a  time, so an even number of digits is
89              expected. The string of hexadecimal digits may be on the command
90              line  (replacing "H1 H2 H3") or spread across multiple lines the
91              HFN given to --file=.  On the command  line,  spaces  (or  other
92              whitespace  characters)  between sequences of hexadecimal digits
93              are ignored; the maximum command line hex string is 1023 charac‐
94              ters long.
95
96       -s, --status=SS
97              where  SS is a SCSI status byte value, given in hexadecimal. The
98              SCSI status byte is related to, but distinct from, sense data.
99
100       -v, --verbose
101              increase the degree of verbosity (debug messages).
102
103       -V, --version
104              output version string then exit.
105
106       -w, --write=WFN
107              writes the sense data out to a file called WFN. If necessary WFN
108              is  created. If WFN exists then it is truncated prior to writing
109              the sense data to it. If the --hex option  is  also  given  then
110              ASCII  hex is written to WFN (see the --hex option description);
111              otherwise binary is written to WFN. This option is a convenience
112              and may be helpful in converting the ASCII hexadecimal represen‐
113              tation of sense data (or  anything  else)  into  the  equivalent
114              binary or a compilable ASCII hex form.
115

NOTES

117       Unlike  most  utilities in this package, this utility does not access a
118       SCSI device (logical unit). This utility accesses a library  associated
119       with  this package. Amongst other things the library decodes SCSI sense
120       data.
121
122       The sg_raw utility takes a ASCII hexadecimal  sequence  representing  a
123       SCSI  CDB.  When  sg_raw is given the '-vvv' option, it will attempt to
124       decode the CDB name.
125

EXAMPLES

127       Sense data is often printed out in kernel logs  and  sometimes  on  the
128       command line when verbose or debug flags are given. It will be at least
129       8 bytes long, often 18 bytes long but  may  be  longer.  A  sense  data
130       string might look like this:
131
132       f0 00 03 00 00 12 34 0a  00 00 00 00 11 00 00 00
133       00 00
134
135       Cut and paste it after the sg_decode_sense command:
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137         sg_decode_sense f0 00 03 00 00 12 34 0a 00 00 00 00 11 00 00 00 00 00
138
139       and for this sense data the output should look like this:
140
141        Fixed format, current;  Sense key: Medium Error
142        Additional sense: Unrecovered read error
143         Info fld=0x1234 [4660]
144
145       For a medium error the Info field is the logical block address (LBA) of
146       the lowest numbered block that the associated SCSI command was not able
147       to read (verify or write).
148

EXIT STATUS

150       The  exit  status of sg_decode_sense is 0 when it is successful. Other‐
151       wise see the sg3_utils(8) man page.
152

AUTHORS

154       Written by Douglas Gilbert.
155

REPORTING BUGS

157       Report bugs to <dgilbert at interlog dot com>.
158
160       Copyright © 2010-2019 Douglas Gilbert
161       This software is distributed under a FreeBSD license. There is NO  war‐
162       ranty;  not  even  for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
163       POSE.
164

SEE ALSO

166       sg_requests,sg_raw(sg3_utils)
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170sg3_utils-1.45                     June 2019                SG_DECODE_SENSE(8)
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