Provided by: sg3-utils_1.46-1build1_amd64 bug


       sg_requests - send one or more SCSI REQUEST SENSE commands


       sg_requests  [--desc] [--error] [--help] [--hex] [--maxlen=LEN] [--num=NUM] [--number=NUM]
       [--progress] [--raw] [--status] [--time] [--verbose] [--version] DEVICE


       Send SCSI REQUEST SENSE command to DEVICE and output the parameter data response which  is
       expected  to  be  in  sense  data format. Both fixed and descriptor sense data formats are

       Multiple REQUEST SENSE commands can be sent with the --num=NUM option. This  can  be  used
       for timing purposes or monitoring the progress indication.


       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
              recognizes  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 command. 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=LEN
              where  LEN  is  the  (maximum)  response length in bytes. It is placed in the cdb's
              "allocation 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=NUM
              perform  NUM SCSI REQUEST SENSE commands, stopping when either NUM is reached or an
              error occurs. The default value for NUM is 1 .

              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 below.

       -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 ignore 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  additional  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) 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

       -V, --version
              print the version string and then exit.


       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 command.

       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 underway, 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).


       The  exit status of sg_requests is 0 when it is successful. Otherwise see the sg3_utils(8)
       man page.


       Written by Douglas Gilbert.


       Report bugs to <dgilbert at interlog dot com>.


       Copyright © 2004-2017 Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO warranty; not  even  for


       sg_turs (sg3_utils)