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.
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
output the usage message then exit.
output response in ASCII hexadecimal.
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).
perform NUM SCSI REQUEST SENSE commands, stopping when either
NUM is reached or an error occurs. The default value for NUM is
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.
output response in binary (to stdout).
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.
time the SCSI REQUEST SENSE command(s) and calculate the average
number of operations per second.
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.
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