1COMPARE AND WRITE(8) SG3_UTILS COMPARE AND WRITE(8)
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6 sg_compare_and_write - send the SCSI COMPARE AND WRITE command
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9 sg_compare_and_write [--dpo] [--fua] [--fua_nv] [--grpnum=GN] [--help]
10 --in=IF [--inw=WF] --lba=LBA [--num=NUM] [--quiet] [--timeout=TO]
11 [--verbose] [--version] [--wrprotect=WP] [--xferlen=LEN] DEVICE
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14 Send the SCSI COMPARE AND WRITE command to DEVICE. This utility reads a
15 compare buffer and a write buffer from either one or two files. If the
16 --inw=WF option is not given then the concatenated compare and write
17 buffers are read from the file indicated by the --in=IF option. If the
18 --inw=WF option is given then the compare buffer is read from the file
19 indicated by the --in=IF while the write buffer is read from the file
20 indicated by the --inw=WF.
21 Those buffers are expected to each contain NUM blocks of data. The com‐
23 pare starts at logical block address LBA on the DEVICE and if the com‐
24 parison fails (i.e. the provided compare buffer does not equal at LBA
25 on the DEVICE) then the COMPARE AND WRITE command finishes with a sense
26 key of MISCOMPARE. In this case this utility will completes and set an
27 exit status of 14 (which happens to be the sense key value of MISCOM‐
28 PARE).
29 If the comparison succeeds then the provided write buffer is written to
31 starting at LBA for NUM blocks on the DEVICE.
32 The actual number of bytes transferred in the data-out buffer of the
34 COMPARE AND WRITE command may need to be given by the user with the
35 --xferlen=LEN option. LEN defaults to (2 * NUM * 512) which is 1024 for
36 the default NUM of 1. If the block size is other than 512 then the user
37 will need to use --xferlen=LEN option. If protection information is
38 given (indicated by a value of WP other than 0 (the default)) then for
39 a NUM of 1 LEN should be 1040 . Note that the SCSI READ CAPACITY com‐
40 mand is not checked by this utility (e.g. to find the block size).
41 The definition of the SCSI COMPARE AND WRITE command requires that the
43 DEVICE implement the compare and optional write as an uninterrupted
44 series of actions. Depending on some other DEVICE settings a verify
45 operation may occur prior to the compare.
46 When a mismatch occurs between the compare buffer and the blocks start‐
48 ing at LBA read from the DEVICE the sense buffer containing the MISCOM‐
49 PARE sense key causes several messages to be sent to stderr (including
50 the offset of the first byte mismatch). To suppress these messages use
51 the --quiet option. With or without the --quiet option the exit status
52 will be set to 14.
53 This command is defined in SBC-3 whose most recent revision is 36.
55 SBC-3 and other SCSI documents can be found at http://www.t10.org .
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58 Arguments to long options are mandatory for short options as well. The
59 options are arranged in alphabetical order based on the long option
60 name.
61 -d, --dpo
63 Set the DPO bit in the COMPARE AND WRITE CDB
64 -f, --fua
66 Set the FUA bit in the COMPARE AND WRITE CDB
67 -F, --fua_nv
69 Set the FUA_NV bit in the COMPARE AND WRITE CDB. This bit was
70 removed in SBC-3 revision 35d and its position marked as
71 "reserved".
72 -g, --grpnum=GN
74 where GN is the value to be placed in the group number field in
75 the COMPARE AND WRITE CDB.
76 -h, --help
78 output the usage message then exit.
79 -i, --in=IF
81 read data (binary) from file named IF. This will either be the
82 combined compare and write buffers (when the --inw=WF option is
83 not given) or just the compare buffer (when the --inw=WF option
84 is given). If IF is '-' then stdin (e.g. a pipe) is read.
85 -C, --inc=IF
87 The same as the --in option.
88 -D, --inw=WF
90 read data (binary) from file named WF. This will the write buf‐
91 fer that will become the second half of the data-out buffer sent
92 to the DEVICE associated with the COMPARE AND WRITE command.
93 Note that when this option is given then the --in=IF is expected
94 to hold the associated compare buffer.
95 -l, --lba=LBA
97 where LBA is the logical block address to start the COMPARE AND
98 WRITE command. Assumed to be in decimal unless prefixed with
99 '0x' or has a trailing 'h'.
100 -n, --num=NUM
102 where NUM is the number of blocks, starting at LBA, to read and
103 compare with the verify instance. And given a match, the NUM of
104 blocks to write starting LBA. The default value for NUM is 1.
105 -q, --quiet
107 suppress the sense buffer messages associated with a MISCOMPARE
108 sense key that would otherwise be sent to stderr. Still set the
109 exit status to 14 which is the sense key value indicating a MIS‐
110 COMPARE.
111 -t, --timeout=TO
113 where TO is the command timeout value in seconds. The default
114 value is 60 seconds. If NUM is large (or zero) a WRITE SAME com‐
115 mand may require considerably more time than 60 seconds to com‐
116 plete.
117 -v, --verbose
119 increase the degree of verbosity (debug messages).
120 -V, --version
122 output version string then exit.
123 -w, --wrprotect=WP
125 set the WRPROTECT field in the cdb to WP. The default value is 0
126 which implies no protection information is sent (along with the
127 user data) by this utility.
128 -x, --xferlen=LEN
130 where LEN is the data out buffer length in byte. It defaults to
131 (2 * NUM * 512) bytes. If the DEVICE block size is other than
132 512 bytes or WP is non-zero (implying additional protection
133 information) then this default will be incorrect; the use must
134 supply the correct value for LEN
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137 Various numeric arguments (e.g. LBA) may include multiplicative suf‐
138 fixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section
139 in the sg3_utils(8) man page.
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142 The exit status of sg_compare_and_write is 0 when it is successful. If
143 the compare step fails then the exit status is 14. For other exit sta‐
144 tus values see the EXIT STATUS section in the sg3_utils(8) man page.
145 Earlier versions of this utility set an exit status of 98 when there
147 was a MISCOMPARE.
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150 Written by Shahar Salzman. Maintained by Douglas Gilbert. Additions by
151 Eric Seppanen.
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154 Report bugs to shahar.salzman@kaminario.com or dgilbert@interlog.com
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157 Copyright © 2012-2018 Kaminario Technologies LTD
158 Redistribution and use in source and binary forms, with or without mod‐
159 ification, are permitted provided that the following conditions are
160 met:
161 * Redistributions of source code must retain the above copyright
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163 * Redistributions in binary form must reproduce the above copyright
164 notice, this list of conditions and the following disclaimer in the
165 documentation and/or other materials provided with the distribution.
166 * Neither the name of the <organization> nor the names of its contribu‐
167 tors may be used to endorse or promote products derived from this soft‐
168 ware without specific prior written permission.
169 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
171 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
172 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTIC‐
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181
184 sg_xcopy, sg_receive_copy_results(sg3_utils)
185sg3_utils-1.43 August 2018 COMPARE AND WRITE(8)