NAME


sg_read_long - send a SCSI READ LONG command

SYNOPSIS


sg_read_long [--16] [--correct] [--help] [--lba=LBA] [--out=OF] [--pblock] [--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.
-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.

The LBA and BTL (transfer length) arguments may be followed by the following multiplicative suffixes: c C *1; w W *2; b B *512; k K KiB *1,024; KB *1,000; m M MiB *1,048,576; MB *1,000,000; g G GiB *1,073,741,824; and GB *1,000,000,000 . Also a suffix of the form "x<n>" multiplies the leading number by <n>.

Alternatively numerical values can be given in hexadecimal preceded by either "0x" or "0X" (or with a trailing "h" or "H"). When hex numbers are given, multipliers cannot be used.

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 © 2004-2007 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

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