# sg_seek - send SCSI SEEK, PRE-FETCH(10) or PRE-FETCH(16) command - man(8) - [phpMan] [_SG_SEEK_(8)](https://www.chedong.com/phpMan.php/man/SGSEEK/8/markdown) SG3_UTILS [_SG_SEEK_(8)](https://www.chedong.com/phpMan.php/man/SGSEEK/8/markdown) ## NAME sg_seek - send SCSI SEEK, [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) or [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) command ## SYNOPSIS **sg_seek **[_--10_] [_--count=NC_] [_--grpnum=GN_] [_--help_] [_--immed_] [_--lba=LBA_] [_--num-blocks=NUM_] [_--pre-fetch_] [_--readonly_] [_--skip=SB_] [_--time_] [_--verbose_] [_--version_] [_--wrap-offset=WO_] _DEVICE_ ## DESCRIPTION Sends a SCSI [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown), [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) or [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) command to the _DEVICE_. The SEEK command has been obsolete since SBC-2 (2005) but still is supported on some hard disks and even some SSDs (solid state disks). The PRE-FETCH command can be viewed as SEEK's modern replacement. Instead of talking about moving the disk heads to the track containing the sort after LBA, it talks about bringing the sort after LBA (and a given number of blocks) into the disk's cache. Also the PRE-FETCH commands have an IMMED field. The PRE-FETCH commands can report "real" errors but usually they will report one of two "good" statuses. To do this they return the rarely used CONDITION MET status. If the number of blocks does actually fit in the cache (when IMMED=0) or there is enough room in the cache when the command arrives (when IMMED=1) then a CONDITION MET status is returned. If the re‐ quested number of blocks did not fit (IMMED=0) or would not fit (IMMED=1) then status GOOD is returned. So if a disk has a large cache and PRE-FETCH is used sparingly then the command is more likely to return CONDITION MET than GOOD. This presents some SCSI sub-systems with prob‐ lems as due to its rareness they mishandle CONDITION MET and treat it as an error (see NOTES section below). ## OPTIONS Arguments to long options are mandatory for short options as well. ### -T --10 use a 10 byte cdb command, either [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown) or [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) command. In the absence of the _--pre-fetch_ option, the [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown) command is used. If the _--pre-fetch_ option is given without this option then a [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) command is used. ### -c --count _NC_ is the number of commands (one of [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown), [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) or [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown)) that will be executed. The default value is 1. If an error occurs it is noted and the pro‐ gram continues until _NC_ is exhausted. If _NC_ is 0 then options are checked and the _DE‐_ _VICE_ is opened but no commands are sent. ### -g --grpnum _GN_ is the group number, a value between 0 and 63 (in hex: 0x3f). The default value is 0. This option is ignored if the selected command is [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown). ### -h --help output the usage message then exit. ### -i --immed this option only applies to [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) and [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown), setting the IMMED bit. Without this option, the _DEVICE_ returns after it has completed transferring all, or part of, the requested blocks into the cache. If this option is given the _DEVICE_ re‐ turns after it has done sanity checks on the cdb (e.g. making sure the _LBA_ is greater than the number of available blocks) and before it does the transfer into the cache. Note that even when this option is given, the return status from the PRE-FETCH com‐ mands is still either CONDITION MET status (if the cache seems to have enough free space for the transfer) or a GOOD status (if the cache does not seem to have enough free space). ### -l --lba _LBA_ is the starting logical block address that is placed in the command descriptor block (cdb) of the selected command. Note that the _LBA_ field in [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown) and [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) is a 32 bit quantity, while with [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) it is a 64 bit quantity. The default value is 0 . ### -n --num-blocks _NUM_ is the number of blocks, starting at and including _LBA_, to place in the _DEVICE_'s cache. The [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown) command does not use the _NUM_ value. For [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) _NUM_ is a 16 bit quantity, while for [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) it is a 32 bit quantity. The default value is 1 . If _NUM_ is 0 then the _DEVICE_ will attempt to transfer all blocks from the given _LBA_ to the end of the medium. ### -p --pre-fetch this option selects either [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) or [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) commands. With the _--10_ also given, the [PRE-FETCH(10)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/10/markdown) command is selected; without that option [PRE-FETCH(16)](https://www.chedong.com/phpMan.php/man/PRE-FETCH/16/markdown) is se‐ lected. The default (in the absence of this and other 'selecting' options) the [SEEK(10)](https://www.chedong.com/phpMan.php/man/SEEK/10/markdown) command is selected. ### -r --readonly this option sets a 'read-only' flag when the underlying operating system opens the given _DEVICE_. This may not work since operating systems can not easily determine whether a pass-through is a logical read or write operation so they take a risk averse stance and require read-write type _DEVICE_ opens irrespective of what is performed by the pass-through. ### -s --skip _SB_ is the number of logical block addresses to skip, between repeated commands when _NC_ is greater than 1. The default value of _SB_ is 1 . _SB_ may be set to 0 so that all _NC_ PRE-FETCH commands use the same _LBA_. ### -t --time if given the elapsed time to execute _NC_ commands is recorded. This is printed out be‐ fore this utility exits. If _NC_ is greater than 1 then the the "per command" time is also printed. ### -v --verbose increase the level of verbosity, (i.e. debug output). ### -V --version print the version string and then exit. ### -w --wrap-offset _WO_ is the number of blocks, relative to _LBA_, that when exceeded, set the next com‐ mand's logical block address back to _LBA_. Whether this "reset-to-LBA" action occurs depends on the values _NC_ and _SB_. ## NOTES Prior to Linux kernel 4.17 the CONDITION MET status was logged as an error. Recent versions of FreeBSD handle the CONDITION MET status properly. If either the _--count=NC_ or _--verbose_ option is given then a summary line like the following is output: Command count=5, number of condition_mets=3, number of goods=2 before the utility exits. ## EXIT STATUS The exit status of sg_seek is 0 (GOOD) or 25 (CONDITION_MET) when this utility is successful. If multiple commands are executed (e.g. when _NC_ is greater than 1) then the result of the last executed SEEK or PRE-FETCH command sets the exit status. Otherwise see the [sg3_utils(8)](https://www.chedong.com/phpMan.php/man/sg3utils/8/markdown) man page. ## AUTHORS Written by Douglas Gilbert. ## REPORTING BUGS Report bugs to . ## COPYRIGHT Copyright © 2018 Douglas Gilbert This software is distributed under a FreeBSD license. There is NO warranty; not even for MER‐ CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. ## SEE ALSO ### sg_vpd(sg3_utils); sdparm(sdparm) sg3_utils-1.43 September 2018 [_SG_SEEK_(8)](https://www.chedong.com/phpMan.php/man/SGSEEK/8/markdown)