sg_read_attr - send SCSI READ ATTRIBUTE command
sg_read_attr [--cache] [--enumerate] [--ea=EA] [--filter=FL] [--first=FAI] [--help] [--hex] [--in=FN] [--lvn=LVN] [--maxlen=LEN] [--pn=PN] [--quiet] [--raw] [--readonly] [--sa=SA] [--verbose] [--ver- sion] DEVICE
SG_READ_ATTR(8) SG3_UTILS SG_READ_ATTR(8)
NAME
sg_read_attr - send SCSI READ ATTRIBUTE command
SYNOPSIS
sg_read_attr [--cache] [--enumerate] [--ea=EA] [--filter=FL]
[--first=FAI] [--help] [--hex] [--in=FN] [--lvn=LVN] [--maxlen=LEN]
[--pn=PN] [--quiet] [--raw] [--readonly] [--sa=SA] [--verbose] [--ver-
sion] DEVICE
DESCRIPTION
Sends a SCSI READ ATTRIBUTE command to DEVICE and outputs the data
returned. This command was introduced in SPC-3 revision 1 and thus is
applicable to all SCSI devices. In practice it is used mainly for tape
systems. This utility is based on the SPC-5 draft standard, revision 17
(spc5r17.pdf).
OPTIONS
Arguments to long options are mandatory for short options as well.
-c, --cache
sets the CACHE bit in the READ ATTRIBUTE cdb. This instructs the
device server to return cached attributes. By default that bit
is cleared which instructs the device server not to return
cached attributes.
-e, --enumerate
enumerates all known attributes and service actions. Attributes
include an identifier, length, format and a name as defined by
T10. If DEVICE is given then it is ignored.
-E, --ea=EA
where EA is an element address which is placed in the READ
ATTRIBUTE cdb. This field is only found in SMC-2 and SMC-3
drafts for medium changers usually associated with tape
libraries. By default this field is set to zero.
-f, --filter=FL
where FL is an attribute identifier in the range 0 to 65535 or
-1. Attribute identifiers are typically given in hexadecimal in
which case the hex number should be prefixed by "0x" or has a
trailing "h". "-1" is the default value and means 'match all';
for all other values of FL on the matching attribute is output.
-F, --first=FAI
where FAI is the "first attribute identifier" field in the cdb.
It seems as though the intent of this field is that only
attributes whose identifiers are equal to or greater than FAI
are returned. The default value of FAI is zero. Attributes are
returned in ascending identifier order.
-h, --help
output the usage message then exit.
-H, --hex
output the response in hexadecimal to stdout. When used once the
whole response is output in ASCII hexadecimal with a leading
address (starting at 0) on each line. When used twice each
attribute descriptor in the response is output separately in
hexadecimal. When used thrice the whole response is output in
hexadecimal with no leading address (on each line).
Output generated by '-HHH' (or --hex used three times) can be
redirected to a file. That file will be in suitable format for
--in=FN to use in a later invocation.
-i, --in=FN
FN is treated as a file name (or '-' for stdin) which contains
ASCII hexadecimal or binary representing the response to a READ
ATTRIBUTE command with service action 0x0 (i.e (fetch) attribute
values). When this option is given then DEVICE (if also given)
is ignored.
By default FN is assumed to contain ASCII hexadecimal arranged
as bytes which a space, tab or comma delimited. All characters
from (and including) "#" to the end of line are ignored. If the
--raw option is also given then FN is assumed to contain binary
data. When the --raw option is given then after processing the
input the internal raw variable is reset to 0 so it has no
effect on the output.
Since the READ ATTRIBUTE response does not contain the service
action number that it is a response to, then the --sa=SA should
be given (if not service action 0 (attribute values) is assumed.
-l, --lvn=LVN
where LVN is placed in the "logical volume number" field of the
cdb. The default value is zero which is required to be the log-
ical volume number if the device only has one volume.
-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 8192 is used. The maximum allowed value of LEN
is 1048576.
-p, --pn=PN
where PN is placed in the "partition number" field of the cdb.
If the DEVICE only has one partition then its partition number
must be zero. The default value of PN is zero.
-q, --quiet
this option reduces the amount of information output. For exam-
ple when used once (SA=0), it suppresses the header line
announcing the output of attributes; when used twice it sup-
presses the name of each attribute, leaving only the associated
attribute values (or strings).
-r, --raw
output the SCSI response (i.e. the data-out buffer) in binary
(to stdout).
-R, --readonly
open the DEVICE read-only (e.g. in Unix with the O_RDONLY flag).
The default is to open it read-write.
-s, --sa=SA
where SA is placed on the "service action" field of the cdb.
Values of 0 to 63 are accepted with a default of 0. spc5r08.pdf
defines five service actions: 0 for attributes values ; 1 for an
attribute list (names, not values), 2 for the logical volume
list; 3 for the partition list; 4 is restricted for SMC-3; and 5
for the supported attribute list.
Alternatively an acronym can be given for SA. The acronym should
be one of "av", "al", "lvl", "pn", "smc" or "sa" for service
actions 0 to 5 respectively. The acronyms can also be given in
upper case.
-v, --verbose
increase the level of verbosity, (i.e. debug output).
-V, --version
print the version string and then exit.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | system/storage/sg3_utils |
+---------------+--------------------------+
|Stability | Pass-through uncommitted |
+---------------+--------------------------+
NOTES
Only tape systems seem to implement the SCSI READ ATTRIBUTE command.
The vast majority of its definition is in the SPC standard so other
device types could use it.
Much of the information provided by READ ATTRIBUTE can also be found in
pages returned by LOG SENSE (see the sg_logs utility) and in the VPD
pages returned by the INQUIRY command.
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from http://sg.danny.cz/sg/p/sg3_utils-1.46.tgz.
Further information about this software can be found on the open source
community website at http://sg.danny.cz/sg/sg3_utils.html.
EXAMPLES
To list the attributes of a tape drive whose DEVICE is /dev/sg1 , the
following could be used:
# sg_read_attr -s al /dev/sg1
Attribute list:
Remaining capacity in partition [MiB]
Maximum capacity in partition [MiB]
TapeAlert flags
Load count
MAM space remaining [B]
Assigning organization
Format density code
...
To check the number of partitions:
# sg_read_attr -s pl /dev/sg1
Partition number list:
First partition number: 0
Number of partitions available: 2
And to see the attribute values (which is the default service action):
# sg_read_attr /dev/sg1
Attribute values:
Remaining capacity in partition [MiB]: 1386103
Maximum capacity in partition [MiB]: 1386103
TapeAlert flags: 0
....
To redirect the attribute values response to a file for later decoding:
# sg_read_attr -HHH /dev/sg1 > av.hex
And later the response held in the av.hex file could be decoded with:
# sg_read_attr -s av --in=av.hex
Attribute values:
Remaining capacity in partition [MiB]: 1386103
Maximum capacity in partition [MiB]: 1386103
TapeAlert flags: 0
....
EXIT STATUS
The exit status of sg_read_attr 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 (C) 2016-2020 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
sg_vpd,sg_logs(sg3_utils)
sg3_utils-1.46 December 2020 SG_READ_ATTR(8)