Bash script questions for tape drive control mt and mtx

4evernoob · 08-25-2016, 03:38 PM

Trying to monitor the status of a tape drive with mt and mtx and I'm looking for a way to parse the output and resolve to an answer to "the question".
First question, "is the tape drive busy"? mt will return:

[root@c7 ~]# mt -f /dev/nst0 status
/dev/nst0: Device or resource busy

I tried to capture that in a variable:
[root@c7 ~]# TapeTest=$(mt -f /dev/nst0 status)
/dev/nst0: Device or resource busy
[root@c7 ~]# echo $TapeTest
[root@c7 ~]#
The output inexplicably refuses to be captured here. I figured there are some folks here that could make easy work of this problem. I have most of the script written for what I'm doing but have run into a need to check some of this for control.

Test for tape drive status. Possible outputs for mt -f /dev/nst0 status is:
/dev/nst0: Device or resource busy
or
SCSI 2 tape drive:
File number=-1, block number=-1, partition=0.
Tape block size 0 bytes. Density code 0x0 (default).
Soft error count since last status=0
General status bits on (10000):
IM_REP_EN

I'm thinking key word busy should get this so I need a go no go test for it.

Next item is checking to see which tape is loaded in tape drive.
mtx -f /dev/sg13 status
Storage Changer /dev/sg13:1 Drives, 17 Slots ( 0 Import/Export )
Data Transfer Element 0:Full (Storage Element 1 Loaded):VolumeTag = 000115S
Storage Element 1:Empty
Storage Element 2:Full :VolumeTag=000118S
Storage Element 3:Full :VolumeTag=000119S
Storage Element 4:Full :VolumeTag=000120S
Storage Element 5:Full :VolumeTag=000121S
Storage Element 6:Full :VolumeTag=000122S
Storage Element 7:Full :VolumeTag=000123S
Storage Element 8:Full :VolumeTag=000124S
Storage Element 9:Full :VolumeTag=000125S
Storage Element 10:Full :VolumeTag=000126S
Storage Element 11:Full :VolumeTag=000127S
Storage Element 12:Full :VolumeTag=000128S
Storage Element 13:Full :VolumeTag=000129S
Storage Element 14:Full :VolumeTag=000130S
Storage Element 15:Full :VolumeTag=000131S
Storage Element 16:Full :VolumeTag=000132S
Storage Element 17:Full

Need to resolve out to variables which storage element is empty and if none of them are then there must not be a tape in the drive and storage element 1 loaded with what volumeTag.

Show me your ninja.

Thanks in advance.

michaelk · 08-25-2016, 06:59 PM

In the case of the drive being busy mt writes to stderr and not stdout which is why echo $TapeTest does not output anything. Its been awhile and I do not have a tape drive connected to a running system at the moment so I can not confirm that the normal status writes to stdout. So here is part I

You can capture stdout and stderr via the command

Code:

TapeTest=$( mt -f /dev/st0 2>&1 )

Code:

And you should be able check via regex
if [[ $tapetest =~ [busy]$ ]]; then

fi

4evernoob · 08-25-2016, 08:00 PM

Cool thanks!
This is what I have so far. At least I think so. Tape drive busy backing up so I can't test this yet against a non busy tape drive. Confidence is high though.

while true; do
TapeTest=$(mt -f /dev/nst0 status 2>&1)
if [[ $TapeTest =~ [busy]$ ]]; then
echo sleeping 10sec
sleep 10
else
break
fi
done

Ok now to tackle what tape is loaded and from what slot.

???

4evernoob · 08-25-2016, 11:07 PM

Ok so I have the slot figured out however I could use some help cutting this down to just the number.

[root@c7 backup]# ChangerTest=$( mtx -f /dev/sg13 status |egrep -v -w 'Full|Drives' )
[root@c7 backup]# echo $ChangerTest
Storage Element 5:Empty
[root@c7 backup]#

Still need to get that VolumeTag. Anyone?

4evernoob · 08-26-2016, 01:15 PM

Golden!

[root@c7 scripts]# VOLTAG=$( mtx -f /dev/sg13 status |grep Loaded.*VolumeTag |awk '{ print $10 }' )
[root@c7 scripts]# GNGRSLOT=$( mtx -f /dev/sg13 status |grep Loaded.*VolumeTag |awk '{ print $7 }' )
[root@c7 scripts]# echo "Changer slot = $GNGRSLOT"
Changer slot = 7
[root@c7 scripts]# echo "VolumeTag = $VOLTAG"
VolumeTag = 000123S

For the next guy.
I'm out.