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SG_READ_LONG(8) SG3_UTILS SG_READ_LONG(8)
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 std-
out or placed in a file. Note that the data returned includes the logical block data (typ-
ically 512 bytes for a disk) plus ECC information (whose format is proprietary) plus op-
tionally other proprietary data. Note that the logical block data may be encoded or en-
crypted.
In SBC-4 revision 7 the SCSI READ LONG (10 and 16 byte) commands were made obsolete. In
the same revision all uses of SCSI WRITE LONG (10 and 16 byte) commands were made obsolete
apart from the case in which the WR_UNCOR bit is set.
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 dec-
imal 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_reas-
sign" 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 (C) 2004-2016 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
sg3_utils-1.42 November 2015 SG_READ_LONG(8)
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