Moving Data from Tape to System directory

brent21090 · 02-10-2011, 08:59 AM

I need help writing a script that will copy everything from tape to system directory. I have a Linux box with 3 TB of Hardware space. I am using the following commands
1) mt –f /dev/st0 rewind
2) tar –xvf /dev/st0
3) tar –xvf /dev/st0 fsf 1 (Using this to move to the next segment of the tape)
and then
4) tar -xvf/dev/st0

I keep repeating steps 3 and 4.
Thank you for your help

schneidz · 02-10-2011, 09:12 AM

Code:

while [ 1 ]
do
 ...
done

crts · 02-10-2011, 09:26 AM

Quote:

Originally Posted by brent21090

I need help writing a script that will copy everything from tape to system directory. I have a Linux box with 3 TB of Hardware space. I am using the following commands
1) mt -f /dev/st0 rewind
2) tar -xvf /dev/st0
3) tar -xvf /dev/st0 fsf 1 (Using this to move to the next segment of the tape)
and then
4) tar -xvf/dev/st0

I keep repeating steps 3 and 4.
Thank you for your help

Hi,

do you actually mean

Code:

mt -f /dev/st0 fsf 1

instead of

Code:

tar -xvf /dev/st0 fsf 1  # I *think* this is wrong

Anyway, I do not have a tape drive. So I will have to make some assumptions here, i.e. if the last record has been read then

Code:

mt -f /dev/st0 fsf 1

will exit with error-status 2.

So here goes:

Code:

#!/bin/bash
mt -f /dev/st0 rewind
if [[ $? == 0 ]]; then
   while [[ $? == 0 ]];do
      tar -xvf /dev/st0
      mt -f /dev/st0 fsf 1 # Using this to move to the next segment of the tape
   done
else
   echo 'Error: Could not rewind device: /dev/st0'
fi

UNTESTED! Obviously, since I do not have a tape drive!

And here is something to read about positional parameters if you have more than one tape device or the device name changes for some reason.
http://tldp.org/LDP/abs/html/othertypesv.html

You could then rewrite the script to take the device name as parameter.

brent21090 · 02-10-2011, 10:47 AM

Hi CRTS
Yes I actually meant mt -f /dev/st0 fsf 1
Question: I am not clear as to what '[[$? ==0]];' means.
I have one tape device.
Since this is my 1st time using Linux commands what does 'if' mean at the end of the script you provided?
Thanks for your help.

crts · 02-10-2011, 11:32 AM

Quote:

Originally Posted by brent21090

Hi CRTS
Yes I actually meant mt -f /dev/st0 fsf 1
Question: I am not clear as to what '[[$? ==0]];' means.

Ok, first of all you use a "funny" sign to pass the options. It is supposed to be a '-' (minus) when specifying options. Yours was longer. I copy+pasted your text and so I had that error in the above script, too. But I corrected that now.

As for your questions:

Code:

[[$? ==0]]

This is not correct. The spaces are important; otherwise you will get an error. As for the meaning of

Code:

[[ $? == 0 ]]
  ^       ^ spaces are important

This is simply a test. The '$?' holds the exit value of the last executed command. A value of 0 usually indicates that the command succeeded. We check this value to determine if the mt command succeeded. I assume that it will set an exit status of 2 if there are no more files on the tape. See the manpage of mt for that:

Code:

man mt

So the while-loop will keep executing until mt has read the last file.
The test-condition for the loop is

Code:

[ $? == 0 ]

This is nearly the same as '[[ $? == 0 ]]'. Thinking about it, this test should also be in double brackets '[['. They are more 'robust' then the single ones. I corrected that, too.

Quote:

what does 'if' mean at the end of the script you provided?
Thanks for your help.

That is NOT a mistyped 'if' but it is indeed a 'fi'. It simply indicates the end of the 'if' construct. Its c++ equivalent, e.g, would be the closing curly brace '}'.

brent21090 · 02-11-2011, 02:45 PM

Resolved. Thanks