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       sg_requests - send one or more SCSI REQUEST SENSE commands


       sg_requests   [--desc]   [--help]  [--hex]  [--maxlen=LEN]  [--num=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 supported.

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


       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.

       -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 .

       -p, --progress
              show  progress  indication  (a  percentage)  if  available.   If
              --number=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 verbosity.

       -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.  More  recent  standards  seem  to
       suggest the SCSI REQUEST SENSE command should be used instead.


       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 © 2004-2008 Douglas Gilbert
       This software is distributed under  a  FreeBSD  license.  There  is  NO
       warranty;  not  even  for  MERCHANTABILITY  or FITNESS FOR A PARTICULAR