SG_WRITE_X(8) SG3_UTILS SG_WRITE_X(8)
NAME
sg_write_x - SCSI WRITE normal/ATOMIC/SAME/SCATTERED/STREAM, ORWRITE
commands
SYNOPSIS
sg_write_x [--16] [--32] [--app-tag=AT] [--atomic=AB] [--bmop=OP,PGP]
[--bs=BS] [--combined=DOF] [--dld=DLD] [--dpo] [--dry-run] [--fua]
[--generation=EOG,NOG] [--grpnum=GN] [--help] --in=IF
[--lba=LBA[,LBA...]] [--normal] [--num=NUM[,NUM...]] [--off-
set=OFF[,DLEN]] [--or] [--quiet] [--ref-tag=RT] [--same=NDOB]
[--scat-file=SF] [--scat-raw] [--scattered=RD] [--stream=ID] [--strict]
[--tag-mask=TM] [--timeout=TO] [--unmap=U_A] [--verbose] [--version]
[--wrprotect=WPR] DEVICE
Synopsis per supported command:
sg_write_x --normal --in=IF [--16] [--32] [--app-tag=AT] [--bs=BS]
[--dld=DLD] [--dpo] [--fua] [--grpnum=GN] [--lba=LBA] [--num=NUM]
[--offset=OFF[,DLEN]] [--ref-tag=RT] [--strict] [--tag-mask=TM]
[--timeout=TO] [--wrprotect=WPR] DEVICE
sg_write_x --or --in=IF [--16] [--32] [--bmop=OP,PGP] [--bs=BS] [--dpo]
[--fua] [--generation=EOG,NOG] [--grpnum=GN] [--lba=LBA] [--num=NUM]
[--offset=OFF[,DLEN]] [--strict] [--timeout=TO] [--wrprotect=OPR] DE-
VICE
sg_write_x --atomic=AB --in=IF [--16] [--32] [--app-tag=AT] [--bs=BS]
[--dpo] [--fua] [--grpnum=GN] [--lba=LBA] [--num=NUM] [--off-
set=OFF[,DLEN]] [--ref-tag=RT] [--strict] [--timeout=TO] [--wrpro-
tect=WPR] DEVICE
sg_write_x --same=NDOB [--16] [--32] [--app-tag=AT] [--bs=BS] [--dpo]
[--fua] [--grpnum=GN] [--in=IF] [--lba=LBA] [--num=NUM] [--off-
set=OFF[,DLEN]] [--ref-tag=RT] [--strict] [--timeout=TO] [--unmap=U_A]
[--wrprotect=WPR] DEVICE
sg_write_x --scattered=RD --in=IF [--16] [--32] [--app-tag=AT]
[--bs=BS] [--dld=DLD] [--dpo] [--fua] [--grpnum=GN]
[--lba=LBA[,LBA...]] [--num=NUM[,NUM...]] [--offset=OFF[,DLEN]]
[--ref-tag=RT] [--scat-file=SF] [--scat-raw] [--strict] [--tag-mask=TM]
[--timeout=TO] [--wrprotect=WPR] DEVICE
sg_write_x --stream=ID --in=IF [--16] [--32] [--app-tag=AT] [--bs=BS]
[--dpo] [--fua] [--grpnum=GN] [--lba=LBA] [--num=NUM] [--off-
set=OFF[,DLEN]] [--ref-tag=RT] [--strict] [--tag-mask=TM] [--time-
out=TO] [--wrprotect=WPR] DEVICE
DESCRIPTION
This utility will send one of six SCSI commands, all associated with
writing data to the given DEVICE. They are a "normal" WRITE, ORWRITE,
WRITE ATOMIC, WRITE SAME, WRITE SCATTERED or WRITE STREAM. This utility
supports the 16 and 32 byte variants of all six commands. Hence some
closely related commands are not supported (e.g. WRITE(10)). All 32
byte variants, apart from ORWRITE(32), require the DEVICE to be format-
ted with type 1, 2 or 3 Protection Information (PI), making all logical
blocks 8 bytes (or a multiple of 8 bytes) longer on the media.
The command line interface is a little crowded with over thirty op-
tions. Hence the SYNOPSIS, after listing all the (long) options, lists
those applicable to each supported command. For each command synopsis,
the option that selects the SCSI command is shown first followed by any
required options. If no command option is given then a "normal" WRITE
is assumed. Even though the --scat-file=SF option can be given for
every command, it is only shown for WRITE SCATTERED where it is most
useful. If the --scat-file=SF option is given then neither the
--lba=LBA[,LBA...] nor the --num=NUM[,NUM...] options should be given.
Only the first item of the --lba=LBA[,LBA...] and the
--num=NUM[,NUM...] options (or first pair (or quintet) from the
--scat-file=SF option) is used for all but the WRITE SCATTERED command.
All commands can take --dry-run and --verbose in addition to those
shown in the SYNOPSIS.
The logical block size in bytes can be given explicitly with the
--bs=BS option, as long as BS is greater than zero. It is typically a
power of two, 512 or greater. If the --bs=BS option is not given or BS
is zero then the SCSI READ CAPACITY command is used to find the logical
block size. First the READ CAPACITY(16) command is tried and if suc-
cessful the logical block size in the response is typically used as the
actual block size for this utility. The exception is when PROT_EN is
set in the response and the --wrprotect=WPR option is given and
non-zero; in which case 8 (bytes) is added to the logical block size to
yield the actual block size used by this utility. If READ CAPACITY(16)
fails then READ CAPACITY(10) is tried and if that works then the logi-
cal block size in the response is used as the actual block size.
The number of bytes this utility will attempt to read from the file
named by IF is the product of the actual block size and the num-
ber_of_blocks (NUM or the sum of NUM arguments). If less bytes are read
from the file IF and the --strict option is given then this utility ex-
its with an exit status of SG_LIB_FILE_ERROR. If less bytes are read
from the file IF and the --strict option is not given then bytes of
zero are substituted for the "missing" bytes and this utility contin-
ues.
Attempts to write multi megabyte data with a single command are likely
to fail for one of several reasons. First the operating system might
object to allocating a buffer that large. Next the SCSI pass-through
usually limits data blocks to a few megabytes or less. Finally the
storage device might have a limited amount of RAM to support a write
operation such as atomic (as it may need to roll back). The storage de-
vice can inform the application client of its limitations via the block
limits VPD page (0xb0), with the maximum atomic transfer length field
amongst others.
A degenerate LBA (Logical Block Address) range descriptor with no PI
has an LBA and NUM of zero. A degenerate LBA range descriptor with PI
additionally has its RT, AT and TM fields set to zero (note: that is
not the default values for RT, AT and TM). They are degenerate in the
sense that they are indistinguishable from a pad of zeros that follow
the scatter list in the data-out buffer. SBC-4 makes clear that a de-
generate LBA range descriptor is valid. This may become an issue if RD
given in the --scattered=RD option has the value 0. In this case the
logic may need to scan the user provided data to calculate the number
of LBA range descriptors which is required by the WRITE SCATTERED cdb.
In the absence of other information the logic will take a degenerate
LBA range descriptor as a terminator of the scatter list.
The current reference for these commands is draft SBC-4 (T10/BSR INCITS
506) revision 15 dated 9 November 2017. All six SCSI commands are de-
scribed in that document. WRITE ATOMIC was added in SBC-4 revision 3;
WRITE STREAM was added in SBC-4 revision 7; WRITE SCATTERED was added
in SBC-4 revision 11 while the others are in the SBC-3 standard.
OPTIONS
Arguments to long options are mandatory for short options as well. The
options are arranged in alphabetical order based on the long option
name.
-6, --16
send the 16 byte cdb variant of the selected SCSI command. If no
command is selected then the (normal) SCSI WRITE(16) command is
sent. If neither this option nor the --32 option is given then
this option is assumed.
-3, --32
send the 32 byte cdb variant of the selected SCSI command. If no
command is selected then the (normal) SCSI WRITE(32) command is
sent. If neither this option nor the --16 option is given then
then the --16 option is assumed. If both this option and the
--16 option are given then this option takes precedence. Note
that apart from ORWRITE(32) all other 32 byte cdb variants re-
quire a DEVICE formatted with type 1, 2 or 3 protection informa-
tion.
-a, --app-tag=AT
where AT is the "expected logical block application tag" field
found in most of the 32 byte cdb variants (the exception is OR-
WRITE(32)). AT is a 16 bit field which means the maximum value
is 0xffff. The default value is 0xffff .
-A, --atomic=AB
selects the WRITE ATOMIC command and AB is placed in the Atomic
Boundary field of its cdb. It is a 16 bit field so the maximum
value is 0xffff. If unsure what value to set, try 0 which will
attempt to write the whole data-out buffer in a single atomic
operation.
-B, --bmop=OP,PGP
where OP and PGP are the values to be placed in ORWRITE(32)'s
BMOP and 'Previous Generation Processing' fields respectively.
BMOP is a 3 bit field (ranges from 0 to 7) and PGP is a 4 bit
field (ranges from 0 to 15). Both fields default to 0.
-b, --bs=BS
where BS is the logical block size or the actual block size
which will be slightly bigger. The default value is zero. If
this option is not given or is given with a BS of zero then the
SCSI READ CAPACITY(16) command is sent to DEVICE. If that fails
then the READ CAPACITY(10) command is sent. The logical and ac-
tual block size will be derived from the response of the READ
CAPACITY command.
This section assumes BS is greater than zero. If BS is less than
512 (bytes) or not a multiple of 8, a warning is issued and the
utility continues unless the --strict option is also given. If
BS is a power of two (e.g. 512) then the logical and actual
block size is set to BS (e.g. 512). If BS is not a power of two
(e.g. 520) then the logical block size is set to the closest
power of two less than BS (e.g. 512) and the actual block size
is set to BS (e.g. 520).
If the logical and actual block size are different then a later
check will reduce the actual block size back to the logical
block size unless --wrprotect=WPR is greater than zero.
-c, --combined=DOF
This option only applies to WRITE SCATTERED and assumes the
whole data-out buffer can be read from IF given by the --in=IF
option. The whole data-out buffer is the parameter list header,
followed by zero or more LBA range descriptors, optionally fol-
lowed by some pad bytes and then the data to be written to the
media. If the --lba=LBA[,LBA...], --num=NUM[,NUM...] or
--scat-file=SF options are also given then an error is gener-
ated. The DOF argument should be the value suitable for the
'Logical Block Data Offset' field in the WRITE SCATTERED cdb.
This is the offset in the data-out buffer where the data to
write to the media commences. The unit of that field is the ac-
tual block size which is the logical block size plus a multiple
of 8, if protection information (PI) is being sent. When WPR
(from --wrprotect=WPR) is greater than zero then PI is expected.
SBC-4 revision 15 does not state it but it would appear that a
DOF value of 0 is invalid. It is suggested that this option be
used with the --strict option while experimenting as random or
incorrect data fed in via the --in=IF option could write a lot
of "interesting" data all over the DEVICE. If DOF is given as 0
the utility will scan the data in IF until RD LBA range descrip-
tors are found; or if RD is also 0 until a degenerate LBA range
descriptor is found.
-D, --dld=DLD
where DLD is the duration limits descriptor spread across 3 bits
in the SCSI WRITE(16) and the WRITE SCATTERED(16) cdbs. DLD is
between 0 to 7 inclusive with a default of zero. The DLD0 field
in WRITE(16) and WRITE SCATTERED(16) is set if (0x1 & DLD) is
non-zero. The DLD1 field in both cdbs is set if (0x2 & DLD) is
non-zero. The DLD2 field in both cdbs is set if (0x4 & DLD) is
non-zero.
-d, --dpo
if this option is given then the DPO (disable page out) bit
field in the cdb is set. The default is to clear this bit field.
Applies to all commands supported by thus utility except WRITE
SAME.
-x, --dry-run
this option exits (with a status of 0) just before it would oth-
erwise send the selected SCSI write command. It may still send a
SCSI READ CAPACITY command (16 byte variant and perhaps 10 byte
variant as well) so the DEVICE is still required. It reads the
data in and processes it if the --in=IF and/or the
--scat-file=SF options are given. All command line processing
and sanity checks (e.g. if the --strict option is given) will be
performed and if there is an error then there will be a non zero
exit status value.
If this option is given twice (e.g. -xx) then instead of per-
forming the selected write SCSI command, the data-out buffer is
written to a file called sg_write_x.bin . If it doesn't exist
then that file is created in the current directory and is trun-
cated if it previously did exist with longer contents. The
data-out buffer is written in binary with some information about
it written to stdout. For writes other than scattered the file-
name and its length in bytes is output to stdout. For write
scattered additionally its number of LBA range descriptors and
its logical block data offset written to stdout.
-f, --fua
if this option is given then the FUA (force unit access) bit
field in the cdb is set. The default is to clear this bit field.
Applies to all commands supported by thus utility except WRITE
SAME.
-G, --generation=EOG,NOG
the arguments for this option are used by the ORWITE(32) command
only. EOG is placed in the "Expected ORWgeneration" field while
NOG is placed in the "New ORWgeneration" field. Both are 32 bits
long and default to zero.
-g, --grpnum=GN
sets the 'Group number' field to GN. Defaults to a value of
zero. GN should be a value between 0 and 63.
-h, --help
output the usage message then exit. Use multiple times for more
help. Currently '-h' to '-hhhh' provide different output.
-i, --in=IF
read data (in binary) from a file named IF in a single OS system
call (in Unix: read(2)). That data is placed in a continuous
buffer and then used as the data-out buffer for all SCSI write
commands apart from WRITE SCATTERED(16 or 32) which may include
other data in the data-out buffer. For WRITE SCATTERED (16 or
32) the data-out buffer is made up of 3 or 4 components in this
order: a parameter list header (32 zero bytes); zero or more LBA
range descriptors, optionally some pad bytes (zeros) and then
data to write to the media. For WRITE SCATTERED IF only provides
the data to write to the media unless --combined=DOF is given.
When the --combined=DOF option is given IF contains all compo-
nents of the WRITE SCATTERED data-out buffer in binary. The data
read from IF starts from byte offset OFF which defaults to zero
and no more than DLEN bytes are read from that point (i.e. from
the file byte offset OFF). If DLEN is zero or not given the rest
of the file IF is read. This option is mandatory apart from when
--same=1 is given (that sets the NDOB bit which stands for "No
Data Out Buffer"). In Unix based OSes, any number of zeros can
be produced by using the /dev/zero device file.
IF may be "-" which is taken as stdin. In this case the --off-
set=OFF,DLEN can be given with OFF set to 0 and LEN set to a
non-zero value, preferably a multiple of the actual block size.
The utility can also deduce how long the IF should be from NUM
(or the sum of them in the case of a scatter list).
-l, --lba=LBA[,LBA...]
where the argument is a single Logical Block Address (LBA) or a
comma separated list of LBAs each of which is the address of the
first block written by the selected write command. Only the
WRITE SCATTERED command can usefully take more than one LBA.
Whatever number of LBAs is given, there needs to be an equal
number of NUMs given to the --num=NUM[,NUM...] option. The first
given LBA joins with the first given NUM to form the first LBA
range descriptor (which T10 number from zero in SBC-4). The sec-
ond LBA joins with the second LBA to form the second LBA range
descriptor, etc. A more convenient way to define a large number
of LBA range descriptors is with the --scat-file=SF option. De-
faults to logical block 0 (which could be dangerous) while NUM
defaults to 0 which makes the combination harmless. LBA is as-
sumed to be in decimal unless prefixed with '0x' or has a trail-
ing 'h'.
-N, --normal
the choice of a "normal" WRITE (16 or 32) command can be made
explicitly with this option. In the absence of selecting any
other command (e.g. --atomic=AB ), the choice of a "normal"
WRITE is the default.
-n, --num=NUM[,NUM...]
where the argument is a single NUMber of blocks (NUM) or a comma
separated list of NUMs that pair with the corresponding entries
in the --lba=LBA[,LBA...] option. If a NUM is given and is not
provided by another method (e.g. by using the --scat-file=SF op-
tion) then it defaults to the number of blocks derived from the
size of the file named by IF (starting at byte offset OFF to the
end or the file or DLEN). Apart from the --combined=DOF option,
an LBA must be explicitly given (either with I--lba=LBA or via
--scat-file=SF), if not NUM defaults to 0 as a safety measure.
-o, --offset=OFF[,DLEN]
where OFF is the byte offset within the file named IF to start
reading from. The default value of OFF is zero which is the be-
ginning of file named IF. DLEN is the maximum number of bytes to
read, starting at byte offset OFF, from the file named IF. Less
bytes will be read if an end of file occurs before DLEN is ex-
hausted. If DLEN is zero or not given then reading from byte
offset OFF to the end of the file named IF is assumed.
-O, --or
selects the ORWRITE command. ORWRITE(16) has similar fields to
WRITE(16) apart from the WRPROTECT field being named ORPROTECT
with slightly different semantics and the absence of the 3 DLD
bit fields. ORWRITE(32) has four extra fields that are set with
the --bmop=OP,PGP and --generation=EOG,NOG options. ORWRITE(32)
is the only 32 byte cdb command in this utility that does not
require a DEVICE formatted with type 1, 2 or 3 PI (although it
will still work if it is formatted with PI).
-Q, --quiet
suppress some informational messages such as the ones associated
with detected errors when this utility is about to exit. The
exit status value is still returned to the operating system when
this utility exits.
-r, --ref-tag=RT
where RT is the "expected initial logical block reference tag"
field found in the 32 byte cdb variants of WRITE, WRITE ATOMIC,
WRITE SAME and WRITE STREAM. The field is also found in the
WRITE SCATTERED(32) LBA range descriptors. It is a 32 bit field
which means the maximum value is 0xffffffff. The default value
is 0xffffffff.
-S, --same=NDOB
selects the WRITE SAME command with the NDOB field set to NDOB
which stands for No Data-Out Buffer. NDOB can take values 0 or 1
(i.e. it is a single bit field). When --same=1 all options asso-
ciated with the data-out buffer are ignored.
-q, --scat-file=SF
where SF is the name of an auxiliary file containing the scatter
list for the WRITE SCATTERED command. If the --scat-raw option
is also given then SF is assumed to contain both the parameter
list header (32 bytes of zeros) followed by zero or more LBA
range descriptors which are also 32 bytes long each. These com-
ponents are as defined by SBC-4 (i.e. in binary with integers
in big endian format). If the --scat-raw option is not given
then a file of ACSII hexadecimal is expected as described in the
SCATTERED FILE ASCII FORMAT section below.
If this option is given with the --combined=DOF option then this
utility will exit with a syntax error. SF must not be "-", a way
of stopping the user trying to redirect stdin.
-R, --scat-raw
this option only effects the way that the file named SF from the
--scat-file=SF option for WRITE SCATTERED is interpreted. By de-
fault (i.e. without this option), SF is parsed as ASCII hexadec-
imal with blank lines and line contents from and including '#'
to the end of line ignored. Hence it can contain comments and
other indications. When this option is given, the file named SF
is interpreted as binary. As binary it is assumed to contain 32
bytes of zeros (the WRITE SCATTERED parameter list header) fol-
lowed by zero or more LBA range descriptors (which are 32 bytes
each). If the --strict option is given the reserved field in
those two items are checked with any non zero bytes causing an
error.
-S, --scattered=RD
selects the WRITE SCATTERED command with RD being the number of
LBA range descriptors that will be placed in the data-out
buffer. If RD is zero then the logic will try and determine the
number of range descriptors by other means (e.g. by parsing the
file named by SF, if there is one). The LBA range descriptors
differ between the 16 and 32 byte cdb variants of WRITE SCAT-
TERED. In the 16 byte cdb variant the 32 byte LBA range descrip-
tor is made up of an 8 byte LBA, followed by a 4 byte num-
ber_of_blocks followed by 20 bytes of zeros. In the 32 byte
variant the LBA and number_of_blocks are followed by a RT (4
bytes), an AT (2 bytes) and a TM (2 bytes) then 12 bytes of ze-
ros.
This paragraph applies when RD is greater than zero. If RD is
less than the number of LBA range descriptors built from command
line options, from the --scat-file=SF option or decoded from IF
(when the --combined=DOF option is given) then RD takes prece-
dence; so RD is placed in the "Number of LBA Range Descriptors"
field in the cdb. If RD is greater than the number of LBA range
descriptors found from the provided data and options, then an
error is generated.
-T, --stream=ID
selects the WRITE STREAM command with the STR_ID field set to
ID. ID can take values from 0 to 0xffff (i.e. it is a 16 bit
field).
-s, --strict
when this option is present, more things (e.g. that reserved
fields contain zeros) and any irregularities will terminate the
utility with a message to stderr and an indicative exit status.
While experimenting with these commands, especially WRITE SCAT-
TERED, it is recommended to use this option.
-t, --tag-mask=TM
where TM is the "logical block application tag mask" field
found in the 32 byte cdb variants of WRITE, WRITE ATOMIC, WRITE
SAME and WRITE STREAM. The field is also found in the WRITE
SCATTERED(32) LBA range descriptors. It is a 16 bit field which
means the maximum value is 0xffff. The default value is 0xffff.
-I, --timeout=TO
where TO is the command timeout value in seconds. The default
value is 120 seconds. If NUM is large on slow media then these
WRITE commands may require considerably more time than 120 sec-
onds to complete.
-u, --unmap=U_A
where U_A is OR-ed bit values used to set the UNMAP and ANCHOR
bit fields in the WRITE SAME (16 or 32) cdb. If U_A is 1 then
the UNMAP bit field is set; if U_A is 2 then the ANCHOR bit
field is set; if U_A is 3 then both the UNMAP and ANCHOR bit
fields are set. The default value for both bit fields is clear
(0); setting U_A to 0 will also clear both bit fields.
-v, --verbose
increase the degree of verbosity (debug messages). These mes-
sages are usually written to stderr.
-V, --version
output version string then exit.
-w, --wrprotect=WPR
sets the WRPROTECT field (3 bits) in all sg_write_x commands
apart from ORWRITE which has a 3 bit ORPROTECT field (and the
synopsis shows OPR to highlight the difference). In all cases
WPR is placed in that 3 bit field. The default value is zero
which does not send any PI in the data-out buffer. WPR should be
a value between 0 and 7.
SCATTERED FILE ASCII FORMAT
All commands in this utility can take a --scat-file=SF and that option
can be seen as a replacement for the --lba=LBA[,LBA...] and
--num=NUM[,NUM...] options. if both the --scat-file=SF and --scat-raw
options are given then the file named SF is expected to be binary and
contain the parameter list header (32 bytes of zeros for both the 16
and 32 byte variants) followed by zero or more LBA range descriptors,
each of 32 bytes each. This section describes what is expected in SF
when the --scat-raw option is not given.
The ASCII hexadecimal "scatter file" (named by SF) can contain com-
ments, empty lines and numbers. If multiple numbers appear on one line
they can be separated by spaces, tabs or a single comma. Numbers are
parsed as decimal unless prefixed by "0x" (or "0X") or have a suffix of
"h". Ox is the prefix of hexadecimal number is the C language while T10
uses the "h" suffix for the same purpose. Anything from and including a
"#" character to the end-of-line is ignored, so comments can be placed
there.
For the WRITE SCATTERED (16) command, its LBA range descriptors contain
two items per descriptor: an 8 byte LBA followed by a 4 byte num-
ber_of_blocks. The remaining 20 bytes of the descriptor are zeros. The
format accepted is relatively loose with each decoded value being
placed in an LBA and then a number_of_blocks until the end-of-file is
reached. The pattern starts with a LBA and if it doesn't finish with a
number_of_blocks (i.e. an odd number of values are parsed) an error
occurs. So the number of LBA range descriptors generated will be half
the number of values parsed in SF.
For the WRITE SCATTERED (32) command, its LBA range descriptors contain
five items per descriptor: an 8 byte LBA followed by a 4 byte num-
ber_of_blocks, then a 4 byte RT, a 2 byte AT, and a 2 byte TM. The last
three items are associated with protection information (PI). The ac-
cepted format in the SF file is more constrained than the 16 byte cdb
variant. The items for each LBA range descriptor must be found on one
line with adjacent items being comma separated. The first two items
(LBA and number_of_blocks) must be given, and if no more items are on
the line then RT, AT and TM are given their default values (all "ff"
bytes). Spaces and tabs may appear between items but commas are the
separators. Two commas with no value between them will cause the "miss-
ing" item to receive its default value.
NOTES
Various numeric arguments (e.g. LBA) may include multiplicative suf-
fixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section
in the sg3_utils(8) man page.
In Linux, prior to lk 3.17, the sg driver did not support cdb sizes
greater than 16 bytes. Hence a device node like /dev/sg1 which is asso-
ciated with the sg driver would fail with this utility if the --32 op-
tion was given (or implied by other options). The bsg driver with de-
vice nodes like /dev/bsg/6:0:0:1 does support cdb sizes greater than 16
bytes since its introduction in lk 2.6.28 .
EXIT STATUS
The exit status of sg_write_x is 0 when it is successful. Otherwise see
the sg3_utils(8) man page.
EXAMPLES
One simple usage is to write 4 blocks of zeros from (and including) a
given LBA according to the rules of WRITE ATOMIC with an atomic bound-
ary of 0. Since no cdb size option is given, the 16 byte cdb will be
assumed (i.e. WRITE ATOMIC(16)):
sg_write_x --atomic=0 --in=/dev/zero --lba=0x1234 --num=4 /dev/sdc
Since --bs=BS has not been given, then this utility will call the READ
CAPACITY(16) command on /dev/sdc to determine the number of bytes in a
logical block. If the READ CAPACITY(16) command fails then the READ CA-
PACITY(10) command is tried. Let us assume one of them works and that
the number of bytes in each logical block is 512 bytes. So 4 blocks of
zeros (each block containing 512 bytes) will be written from (and in-
cluding) LBA 0x1234 . Now to bypass the need for the READ CAPACITY com-
mand(s) the --bs=BS option can be used:
sg_write_x --atomic=0 --bs=512 --in=/dev/zero --lba=0x1234 --num=4
/dev/sdc
Since --bs= is given and its value (512) is a power of 2, then the ac-
tual block size is also 512. If instead 520 was given then the logical
block size would be 512 (the highest power of 2 less than 520) and the
actual block size would be 520 bytes. To send the 32 byte variant add
--32 as in:
sg_write_x --atomic=0 --32 --bs=512 --in=/dev/zero --lba=0x1234
--num=4 /dev/sdc
For examples using 'sg_write_x --same=NDOB' see the manpage for
sg_write_same(8). The syntax is a little different but the semantics
are the same.
To send a WRITE STREAM(32) with a STR_ID of 1 use the following:
sg_write_x --stream=1 --32 --bs=512 --in=/dev/zero --lba=0x1234
--num=4 /dev/sdc
Next is a WRITE SCATTERED(16) command with the scatter list, split be-
tween the --lba= and --num= options, on the command line:
sg_write_x --scattered=2 --lba=2,0x33 --num=4,1 -i /dev/zero
/dev/sg1
Example of a WRITE SCATTERED(16) command with a degenerate LBA range
descriptor (first element to --lba= and --num=):
sg_write_x --scattered=2 --lba=0,0x33 --num=0,1 -i /dev/zero
/dev/sg1
Example of a WRITE SCATTERED(16) command with the scatter list in
scat_file.txt
sg_write_x --scattered=3 -q scat_file.txt -i /dev/zero /dev/sg1
Next a WRITE SCATTERED(16) command with its scatter list and data in a
single file. Note that the argument to --scattered= is 0 so the number
of LBA range descriptors is calculated by analyzing the first two
blocks of scat_data.bin (because the argument to --combined= is 2) :
sg_write_x --scattered=0 --combined=2 -i scat_data.bin /dev/sg1
When the -xx option is used, a WRITE SCATTERED command is not executed
but instead the contents of the data-out buffer are written to a file
called sg_write_x.bin . In the case of WRITE SCATTERED that binary file
is suitable for supplying to a later invocation to do the actual write
to media. For example:
sg_write_x --scattered=3 -q scat_file.txt -xx -i /dev/zero /dev/sg1
Wrote 8192 bytes to sg_write_x.bin, LB data offset: 1
Number of LBA range descriptors: 3
sg_write_x --scattered=0 --combined=1 -i sg_write_x.bin /dev/sg1
Notice when the sg_write_x.bin is written (and nothing is written to
the media), a summary of what has happened is sent to stdout. The value
shown for "LB data offset:" (1) should be given to the --combined= op-
tion when the write to media actually occurs (i.e. the second invoca-
tion shown directly above).
AUTHORS
Written by Douglas Gilbert.
REPORTING BUGS
Report bugs to <dgilbert at interlog dot com>.
COPYRIGHT
Copyright © 2017-2020 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_readcap,sg_vpd,sg_write_same,sg_stream_ctl(sg3_utils)
sg3_utils-1.45 June 2020 SG_WRITE_X(8)
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