traversing /boot/grub/grub.conf

whatis · 11-10-2009, 05:02 AM

Hi

I want to write a command, that will output the default "title" entry from the grub.conf file.

eg: cat /boot/grub/grub.conf | grep title

title Red Hat Enterprise Linux Server (2.6.18-128.1.6.el5)
title Red Hat Enterprise Linux Server (2.6.18-128.el5)

Now supposing the default=1 is set in the file, so I want the output "only" to be the second line.

Plz help with the pipelined command.

gnashley · 11-10-2009, 06:21 AM

grep for 'default' then grep title and use head/tail to limit the output to the desired line

whatis · 11-10-2009, 09:41 PM

Yes,

I already have the value of the 'default'
COUNT=`cat $ /boot/grub/grub.conf | grep default | awk 'BEGIN{FS="="};{print $2}'`

But I dont know how I can use this COUNT to get the corresponding 'title'. I tried using head/tail, but cudnt arrive at a consistent logic which will work for all 'default' values.

There are multiple enteries in my grub.conf file.

ghostdog74 · 11-10-2009, 09:51 PM

use awk

Code:

awk -F"=" '/^default/{val=$2}
/title/{  t[++c]=$0}
c>1{ print c, t[val+1] ;exit}' file

gnashley · 11-11-2009, 01:30 AM

Code:

#!/bin/sh

DEFAULT=$(grep '^default' menu.lst |cut -f2 -d' ')

grep 'title' menu.lst |grep -v '#' |head -n +$DEFAULT |tail -n1

ghostdog74 · 11-11-2009, 01:44 AM

Quote:

Originally Posted by gnashley

Code:

#!/bin/sh

DEFAULT=$(grep '^default' menu.lst |cut -f2 -d' ')

grep 'title' menu.lst |grep -v '#' |head -n +$DEFAULT |tail -n1

does your "default" line have "=" operator ? if yes, then cut is on wrong delimiter.

gnashley · 11-11-2009, 03:45 AM

Mine doesn't. The OP might need to adjust some of the grep commands, depending on how his menu.lst is formatted.
For instance, in mine the line for 'default' has no spaces at the beginning of the line and the value is separated by a space. If he has tabs or '=' then he'd need to adjust that.
And, my lines with 'title' do have spaces at the beginning of the line.
Hopefully, the syntax and spacing is consistent in his menu.lst file. If not, then a more complex solution might be required. I just wanted to offer a non-awk, non-sed solution. Thw whole thing could be done with pure bash, but would be longer.