NAME¶
sg_read_long - send a SCSI READ LONG command
SYNOPSIS¶
sg_read_long [
--16] [
--correct] [
--help]
[
--lba=LBA] [
--out=OF] [
--pblock] [
--readonly]
[
--verbose] [
--version] [
--xfer_len=BTL]
DEVICE
DESCRIPTION¶
Send SCSI READ LONG command to
DEVICE. The read buffer is output in hex
and ASCII to stdout or placed in a file. Note that the data returned includes
the logical block data (typically 512 bytes for a disk) plus ECC information
(whose format is proprietary) plus optionally other proprietary data.
OPTIONS¶
Arguments to long options are mandatory for short options as well.
- -S, --16
- uses a SCSI READ LONG(16) command. The default action is to use a SCSI
READ LONG(10) command. The READ LONG(10) command has a 32 bit field for
the lba while READ LONG(16) has a 64 bit field.
- -c, --correct
- sets the 'CORRCT' bit in the SCSI READ LONG command. When set the data is
corrected by the ECC before being transferred back to this utility. The
default is to leave the 'CORRCT' bit clear in which case the data is not
corrected.
- -h, --help
- output the usage message then exit.
- -l, --lba=LBA
- where LBA is the logical block address of the sector to read.
Assumed to be in decimal unless prefixed with '0x' (or has a trailing
'h'). Defaults to lba 0. If the lba is larger than can fit in 32 bits then
the --16 option should be used.
- -o, --out=OF
- instead of outputting ASCII hex to stdout, send it in binary to the file
called OF. If '-' is given for OF then the (binary) output
is sent to stdout. Note that all informative and error output is sent to
stderr.
- -p, --pblock
- sets the 'PBLOCK' bit in the SCSI READ LONG command. When set the physical
block (plus ECC data) containing the requested logical block address is
read. The default is to leave the 'PBLOCK' bit clear in which case the
logical block (plus any ECC data) is read.
- -r, --readonly
- opens the DEVICE read-only rather than read-write which is the default.
The Linux sg driver needs read-write access for the SCSI READ LONG command
but other access methods may require read-only access.
- -v, --verbose
- increase the level of verbosity, (i.e. debug output).
- -V, --version
- print the version string and then exit.
- -x, --xfer_len=BTL
- where BTL is the byte transfer length (default to 520). If the
given value (or the default) does not match the "long" block
size of the device, the appropriate BTL is deduced from the error
response and printed (to stderr). The idea is that the user will retry
this utility with the correct transfer length.
NOTES¶
If a defective block is found and its contents, if any, has been retrieved then
"sg_reassign" could be used to map out the defective block.
Associated with such an action the number of elements in the "grown"
defect list could be monitored (with "sg_reassign --grown") as the
disk could be nearing the end of its useful lifetime.
Various numeric arguments (e.g.
LBA) may include multiplicative suffixes
or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section in
the
sg3_utils(8) man page.
As a data point, Fujitsu uses a 54 byte ECC (per block) which is capable of
correcting up to a single burst error or 216 bits "on the fly".
[Information obtained from MAV20xxrc product manual.]
EXIT STATUS¶
The exit status of sg_read_long 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 © 2004-2010 Douglas Gilbert
This software is distributed under the GPL version 2. There is NO warranty; not
even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO¶
sg_reassign, sg_write_long, sg_dd