GRUB Append Parameter in-between Quotes

ephemeric has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I would like to append a parameter "transparent_hugepage=never" to the below regex matched line in-between the quotes. On subsequent runs the substitution should be ignored to maintain idempotence (run as an Ansible playbook task). I tried a few things but failed as my knowledge is very limited. Thank you for your help and pardon my poor articulation. Line in question:

GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rhgb quiet"

The sed keeps appending after repeating the play as I can't get the negative lookahead assertion to work, I think that's what it is?

sed '/^GRUB_CMDLINE_LINUX=.*/ s/$.*$"/\1 transparent_hugepage=never"/' $line

And this from the playbook appends after the last quote breaking the config:

                                                                      
+    
replace:                                                              
+          
backup: yes                                                           
+          
dest: /etc/default/grub                                               
+          
regexp: '(^GRUB_CMDLINE_LINUX(?!.*\btransparent_hugepage=never\b).*)$'
+          
replace: '\1 transparent_hugepage=never"'
[download]

Comment on GRUB Append Parameter in-between Quotes Select or Download Code

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Re: GRUB Append Parameter in-between Quotes by shmem (Chancellor) on Sep 09, 2016 at 18:48 UTC
The sed keeps appending after repeating the play as I can't get the negative lookahead assertion to work, I think that's what it is? Maybe that's what it is, and maybe it is because sed doesn't implement it. TIMTOWTDI also applies to sed: `sed '/^GRUB_CMDLINE_LINUX=./ { /transparent_hugepage/! s/$.$"/\1 t +ransparent_hugepage=never"/}' $line` [download] Using perl, things might be easier. perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'	[reply] [d/l]
Re^2: GRUB Append Parameter in-between Quotes by stevieb (Canon) on Sep 10, 2016 at 00:37 UTC
Nice job ++. I took a crack at this with `sed` and perl this afternoon, but was cut short due to a meeting.	[reply] [d/l]
Re^2: GRUB Append Parameter in-between Quotes by ephemeric (Novice) on Sep 12, 2016 at 07:55 UTC
Thank you so much, works! How would one do this in Perl?	[reply]
Re: GRUB Append Parameter in-between Quotes by neilwatson (Priest) on Sep 09, 2016 at 18:48 UTC
How is this a Perl question? Neil Watson watson-wilson.ca	[reply]
Re^2: GRUB Append Parameter in-between Quotes by ephemeric (Novice) on Sep 12, 2016 at 07:50 UTC
I'm sorry, should have said that I can't get it to work in sed and Ansible module, how would one go about doing it in Perl?	[reply]
Re^3: GRUB Append Parameter in-between Quotes by hippo (Archbishop) on Sep 12, 2016 at 08:12 UTC
See perlrun for -p and -e: `echo 'FOO="bar"' \| perl -pe '/^FOO=/ and s/"$/ baz"/;'` [download]	[reply] [d/l]
Re^4: GRUB Append Parameter in-between Quotes by ephemeric (Novice) on Sep 20, 2016 at 09:33 UTC
Re: GRUB Append Parameter in-between Quotes by haukex (Archbishop) on Sep 13, 2016 at 15:36 UTC
Hi ephemeric, A little late but here's a try with Perl. This is like hippo's solution but it adds the detection of whether the parameter has already been added or not. Personally I don't mind breaking up regexes into several regexes if it helps in thinking about the solution. `perl -pe 's/"\s*$/ transparent_hugepage=never"/ if /^GRUB_CMDLINE_LINU +X=/ && !/transparent_hugepage/' filename` [download] Hope this helps, -- Hauke D	[reply] [d/l]
Re^2: GRUB Append Parameter in-between Quotes by ephemeric (Novice) on Sep 20, 2016 at 09:34 UTC
Thank you.	[reply]