# sg_requests - send one or more SCSI REQUEST SENSE commands - man(8) - [phpMan] [_SG_REQUESTS_(8)](https://www.chedong.com/phpMan.php/man/SGREQUESTS/8/markdown) SG3_UTILS [_SG_REQUESTS_(8)](https://www.chedong.com/phpMan.php/man/SGREQUESTS/8/markdown) ## NAME sg_requests - send one or more SCSI REQUEST SENSE commands ## SYNOPSIS **sg_requests **[_--desc_] [_--error_] [_--help_] [_--hex_] [_--maxlen=LEN_] [_--num=NUM_] [_--number=NUM_] [_--progress_] [_--raw_] [_--status_] [_--time_] [_--verbose_] [_--version_] _DEVICE_ ## DESCRIPTION Send SCSI REQUEST SENSE command to _DEVICE_ and output the parameter data response which is ex‐ pected to be in sense data format. Both fixed and descriptor sense data formats are sup‐ ported. Multiple REQUEST SENSE commands can be sent with the _--num=NUM_ option. This can be used for timing purposes or monitoring the progress indication. ## OPTIONS Arguments to long options are mandatory for short options as well. ### -d --desc sets the DESC bit in the REQUEST SENSE SCSI cdb. The _DEVICE_ should return sense data in descriptor (rather than fixed) format. This will only occur if the _DEVICE_ recog‐ nizes descriptor format (SPC-3 and later). If the device is pre SPC-3 then setting a bit in a reserved field may cause a check condition status with an illegal request sense key, but will most likely be ignored. ### -e --error when used once it changes the REQUEST SENSE opcode from 0x3 to 0xff which should be rejected by the _DEVICE_. There is a small chance that the device vendor has implemented a vendor specific command at that opcode (0xff). When used twice the pass-through call to send the SCSI command is bypassed. The idea here is to measure the user space overhead of this package's library to set up and process the response of a SCSI com‐ mand. This option will be typically used with the _--num=NUM_ and _--time_ options where _NUM_ is a large number (e.g. 1000000). ### -h --help output the usage message then exit. ### -H --hex output response in ASCII hexadecimal. ### -m --maxlen where _LEN_ is the (maximum) response length in bytes. It is placed in the cdb's "allo‐ cation length" field. If not given (or _LEN_ is zero) then 252 is used. The maximum value of _LEN_ is 255 (but SPC-4 recommends 252). ### -n --num perform _NUM_ SCSI REQUEST SENSE commands, stopping when either _NUM_ is reached or an er‐ ror occurs. The default value for _NUM_ is 1 . **--number**=_NUM_ same action as _--num=NUM_. Added for compatibility with sg_turs. ### -p --progress show progress indication (a percentage) if available. If _--num=NUM_ is given, _NUM_ is greater than 1 and an initial progress indication was detected then this utility waits 30 seconds before subsequent checks. Exits when _NUM_ is reached or there are no more progress indications. Ignores _--hex_, _--raw_ and _--time_ options. See NOTES section be‐ low. ### -r --raw output response in binary (to stdout). ### -s --status if the REQUEST SENSE command finished without error (as indicated by its SCSI status) then the contents of the parameter data are analysed as sense data and the exit status is set accordingly. The default action (i.e. when this option is not given) is to ig‐ nore the contents of the parameter data for the purposes of setting the exit status. Some types of error set a sense key of "NO SENSE" with non-zero information in the ad‐ ditional sense code (e.g. the FAILURE PREDICTION THRESHOLD EXCEEDED group of codes); this results in an exit status value of 10. If the sense key is "NO SENSE" and both asc and ascq are zero then the exit status is set to 0 . See the [sg3_utils(8)](https://www.chedong.com/phpMan.php/man/sg3utils/8/markdown) man page for exit status values. ### -t --time time the SCSI REQUEST SENSE command(s) and calculate the average number of operations per second. ### -v --verbose increase the level of verbosity, (i.e. debug output). Additionally the response (if received) is output in ASCII-HEX. Use this option multiple times for greater ver‐ bosity. ### -V --version print the version string and then exit. ## NOTES In SCSI 1 and 2 the REQUEST SENSE command was very important for error and warning processing in SCSI. The autosense capability rendered this command almost superfluous. However recent SCSI drafts (e.g. SPC-4 rev 14 and SBC-3 rev 14) increase the utility of the REQUEST SENSE command. Idle and standby (low) power conditions can be detected with this com‐ mand. The REQUEST SENSE command is not marked as mandatory in SPC-3 (i.e. for all SCSI devices) but is marked as mandatory in SBC-2 (i.e. for disks), SSC-3 (i.e. for tapes) and MMC-4 (i.e. for CD/DVD/HD-DVD/BD drives). The progress indication is optionally part of the sense data. When a prior command that takes a long time to complete (and typically precludes other media access commands) is still under‐ way, the progress indication can be used to determine how long before the device returns to its normal state. The SCSI FORMAT command for disks used with the IMMED bit set is an example of an operation that takes a significant amount of time and precludes other media access during that time. The IMMED bit set instructs the FORMAT command to return control to the application client once the format has commenced (see SBC-3). Several long duration SCSI commands associated with tape drives also use the progress indication (see SSC-3). Early standards suggested that the SCSI TEST UNIT READY command be used for polling the progress indication (see the sg_turs utility). Since SPC-3 the standards suggest that the SCSI REQUEST SENSE command should be used instead. The _DEVICE_ is opened with a read-only flag (e.g. in Unix with the O_RDONLY flag). ## EXIT STATUS The exit status of sg_requests is 0 when it is successful. 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 © 2004-2017 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_turs (sg3_utils) sg3_utils-1.45 July 2018 [_SG_REQUESTS_(8)](https://www.chedong.com/phpMan.php/man/SGREQUESTS/8/markdown)