Grab results of GRUB's find command into a shell script variable

kushalkoolwal · 02-02-2009, 03:08 PM

hi,

I am running the following command from my bash shell script:

Code:

#!/bin/bash

/usr/sbin/grub --no-floppy --batch << EOF
find /sbin/init
quit
EOF

Now I know that (manually doing this) GRUB's find command returns the following on bash prompt:

Code:

debian:~#grub --no-floppy
grub> find /sbin/init
 (hd0,8)
grub>

All I want to do is grab the drive letter ("hd0" or whatever grub returns) into a variable in my shell script.

Thanks

burschik · 02-03-2009, 04:54 AM

To capture the output of a program, just use backticks (or an equivalent syntax), like this:

Code:

var=$(grub whatever)

kushalkoolwal · 02-03-2009, 05:05 AM

Quote:

Originally Posted by burschik

To capture the output of a program, just use backticks (or an equivalent syntax), like this:

Code:

var=$(grub whatever)

Thanks for your reply. The thing is that I am trying to run GRUB as a a batch program (--batch) rather than simply a command from my bash shell script. So I am not 100% sure how can I use what you suggested in this case.

Thanks

ntubski · 02-03-2009, 11:38 AM

I think this should work:

Code:

#!/bin/bash

var=$(/usr/sbin/grub --no-floppy --batch << EOF
find /sbin/init
quit
EOF
)

I don't believe the quit command is necessary though, grub will exit when there is no more input. To get just the "hd0":

Code:

var=$(echo find /sbin/init | /usr/sbin/grub --no-floppy --batch | grep -o 'hd[0-9]*')

kushalkoolwal · 02-03-2009, 01:51 PM

Quote:

Originally Posted by ntubski

Code:

var=$(echo find /sbin/init | /usr/sbin/grub --no-floppy --batch | grep -o 'hd[0-9]*')

Hi ntubski,

The code worked just fine. Thanks!

syg00 · 02-03-2009, 04:42 PM

Be prepared for the possibility that your variable may have more than one value in it when you go to use it.

kushalkoolwal · 02-03-2009, 05:04 PM

Quote:

Originally Posted by syg00

Be prepared for the possibility that your variable may have more than one value in it when you go to use it.

Thanks for the heads up. I think I have taken care of that.