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SG_REQUESTS(8)			   SG3_UTILS			SG_REQUESTS(8)

NAME
       sg_requests - send one or more SCSI REQUEST SENSE commands

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

DESCRIPTION
       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 indica‐
       tion.

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) for‐
	      mat. This will only occur if the	DEVICE	recognizes  descriptor
	      format  (SPC-3  and later). If the device is pre SPC-3 then set‐
	      ting a bit in a reserved field may cause a check condition  sta‐
	      tus  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 --num‐
	      ber=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	 indi‐
	      cated  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	 addi‐
	      tional   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).  Addition‐
	      ally 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.

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 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 pre‐
       cludes 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 indica‐
       tion (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 sug‐
       gest the SCSI REQUEST SENSE command should be used instead.

EXIT STATUS
       The exit status of sg_requests 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 © 2004-2012 Douglas Gilbert
       This  software is distributed under a FreeBSD license. There is NO war‐
       ranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PUR‐
       POSE.

SEE ALSO
       sg3_utils

sg3_utils-1.35			 December 2012			SG_REQUESTS(8)
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