Ask Ubuntu General Room

12:03 AM

found my boot options in lenovo's forums where people were raising hell and lenovo seemed to be ignoring them... forums.lenovo.com/t5/Other-Linux-Discussions/… - updated the grub master file with those options and much is better (even though the kernel is 4.18 instead of 4.20 as they seem to insist is required...)

Eliah Kagan

2:02 AM

Spam.

(Smokey didn't detect it. I posted about it in Charcoal HQ but there aren't a lot of people actively watching there at the moment.)

WinEunuuchs2Unix

@EliahKagan I know you are particular. I flag as spam? I down vote? I vote to close? which is best course of action...

@edwinksl hey long time no see!

Eliah Kagan

Assuming you agree it's spam -- I think it pretty clearly is but you should make your own judgment of course -- you should flag it as spam.

WinEunuuchs2Unix

OK flagged as spam. There should be another option "WORST SPAM I'VE EVER SEEN" but no option for that :). Can I vote to close now or does that dilute the gene pool?

Eliah Kagan

I wouldn't VTC it. It should get deleted before it would be closed... and it should definitely get deleted before it would be closed and then have three 20k users casting delete votes on it. Unlike with questions that qualify for closure for the usual reasons, closing a spam question doesn't really improve the situation much, because the goal of most spam is just to be viewed and (for link spam) clicked, not to be answered.

So I think voting to close it doesn't make any difference. You can save your close votes for where they are more needed.

@WinEunuuchs2Unix Regarding that post, I fear my comment may not have been clear. It's the newer versions of Ubuntu on which the command in your answer doesn't work as written, not the older ones. I tested this on 16.04 and 18.04, both of which are fully supported releases, and the version with -d and without quotes in the here string did not work on 18.04.

WinEunuuchs2Unix

2:17 AM

@EliahKagan Well that's weird. It's odd the cut command would fail going forward :( They must have put gnome team on maintenance :)

Eliah Kagan

I don't find it odd. cut is behaving properly. Prior to bash 4.4, bash had a bug where it performed word splitting on expansions in here strings but its documentation claimed it didn't. Ubuntu 16.04 has bash 4.3.

The specific details of why your command doesn't work are in my comment and the linked page, but basically, lsb_release emits tab-delimited output, which you're (intentionally or not) replacing with a space via undocumented version-specific behavior of bash, and then you're telling cut to look for the space.

WinEunuuchs2Unix

Oh it's tab deliminated output. That is why substring on space wasn't working I needed to use $\t or whatever!

Eliah Kagan

Yeah.

Well, you don't need $'\t' or anything. The cut command defaults to using tabs.

WinEunuuchs2Unix

No I meant I tried bash built in substring ${Var##*\ }" and all kinds of derivatives and gave up.

Eliah Kagan

Oh.

Yeah, I wouldn't use anything like that for this.

If you're looking to accept arbitrary whitespace as a delimiter, you could use: awk '{print $2}'

WinEunuuchs2Unix

2:25 AM

Just ask @steeldriver I'm very "awk-challenged" :) That guy is a Wizzard of Awk.

Eliah Kagan

steeldriver is indeed an awk champion. :)

But if you wanted to use awk for this to treat arbitrary whitespace as a delimiter (which is how awk behaves when -F is not passed) then it's as simple as:

NumOnly="$(awk '{print $2}' <<< "$Var")"

WinEunuuchs2Unix

Thanks, I'll revise the answer with it.

Eliah Kagan

But the approach that's closer to what you're doing -- of using cut but having it use the tab -- is fine:

NumOnly="$(cut -f2 <<< "$Var")"

WinEunuuchs2Unix

well double thanks, I'll use that then :)

Eliah Kagan

Whichever you like. That's the main reason I didn't do an edit myself. I wasn't sure if you preferred to use the specific delimiter lsb_release outputs or to use arbitrary whitespace.

You're welcome! :)

In either case, I recommend quoting the parameter expansion in the here string, since that's unfortunately necessary prior to bash 4.4 if one wants to avoid word splitting, and Ubuntu 16.04 has bash 4.3 (and the question is all about detecting multiple Ubuntu releases reliably).

WinEunuuchs2Unix

2:30 AM

Truth be told I've always used -d argument with cut. I didn't release I could leave it off and it would be smarter than me!

Eliah Kagan

Well, without -d it defaults to a tab.

This is unlike awk, which defaults to arbitrary whitespace when -F is not passed.

WinEunuuchs2Unix

I made it two characters shorter using: NumOnly=$(cut -f2 <<< "$Var")

Eliah Kagan

Looks good. I tested it and it works on 16.04 and 18.04 (with the system-provided bash versions).

Eliah Kagan

2:46 AM

I think my comment was confusing because it reads like I was trying to compare 16.04 to older releases, but really I was trying to compare 16.04 to newer releases. (By "basically only works on 16.04" I meant that 16.04 was the only release with current community support on which the word splitting the command relied on occurs.) I think it would be even more confusing now that the answer is improved. So I've just deleted that comment.

Anyway, in case people are interested (since the comments are gone, and also since my comment didn't really clarify this well in the first place): cut works the same in all releases, defaulting to tabs if -d is not used, but bash used to perform word splitting in here strings.

Ubuntu Questions on U&L

7:14 AM

0

Q: How to share an IPv6 connection to the whole LAN?

My ISP still doesn't support IPv6, and I currently use OpenVpn or OpenConnect VPN to get IPv6 connection. Now that there are a Ubuntu server running VPN client, and a OpenWRT router. Is it possible to share (only) the IPv6 connection from the server to the whole LAN network?

dessert

9:57 AM

"This is NOT a subjective question" Yes it is. "Because I dislike using terminal based text editors," is the absolute definition of subjective. Your problem. Fix your attitude towards command line and there is no longer a problem. Command line is the BEST EVER feature created in any OS (<- also subjective :=) ) — Rinzwind 2 hours ago

some like to see the world burn ;)

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Ask Ubuntu General Room