I've long written that you don't want too much swap space because if you try to actively use moreRAM than your machine actually has, swap space basically just givesyou more rope. Your machine is not going to perform very well (orat all) while things are busy frantically paging memory in and out,so it's usually better to just have things fail immediately. Butthere are sensible uses for decent amounts of swap space, even ifthey're relatively rare, and today I

Four Column ASCII ( via ) is a reformattedversion of this Hacker News comment that presents theASCII chart in four columns of 32 characters instead of the usualpresentation of eight columns of 16 (as seen eg here ).A four column representation makes a number of patterns in ASCII(both bit-wise and otherwise) much clearer, for example whyCtrl-Space, Ctrl-@, and Ctrl-` all generally generate a nullbyte .

(I suspect that ASCII is traditionally presented in an 8

You might wonder what happened after we lost both sides of a Linuxsoftware RAID mirror with no advance warning to us . At the time I said thatwe'd merely probably lost the mirror, because maybe one of the diskswould come back to life after we power-cycled the machine. I was beingpretty hopeful in that 'probably'; given that one disk had stronglyfailed and the other one had been giving read errors for some time,I thought it was unlikely that either would be so nice as

Today I tweeted :

Our most commonly detected inbound email virus is now a .doc in a .zipinside another .zip. It's tempting to reject all such emails.

All of the recent ones of these have been what Sophos identifies as'Mal/DrodZp-A' (which means that they're malware, not viruses assuch). The good news is that after discussing the issue, we now rejectsuch emails. One reason we could make this decision easily and withconfidence is that we

We almost certainly just completely lost a software RAID mirrorwith no advance warning (we'll know for sure when we get a chancetomorrow to power-cycle the machine in the hopes that this revivesa drive). This comes as very much of a surprise to us, as we thoughtthat this was not supposed to be possible short of simultaneous twodrive failure out of the blue, which should be an extremely rareevent. So here is what happened, as best we can reconstruct rightnow.

In December

In my entry on what we still use ASCII CR for today , I mentioned in passing that it wasunfortunate that protocols like HTTP had continued to specify thattheir line ending was CR LF instead of plain LF, and called it amistake. Aneurin Price disagreed with this view, citing the historythat CR LF was there first as a line ending. This history isabsolutely true, but it doesn't change that CR LF is a mistake todayand pretty much always was. In fact, we can be more

Yesterday I mentioned in passing that printing a DEL characterdoesn't actually erase anything . This raisesan interesting question, because when you're typing something intoa Unix system and hit your backspace key, Unix sure erases the lastcharacter that you entered. So how is it doing that?

The answer turns out to be basically what you'd expect, althoughthe actual implementation rapidly gets complex. When you hitbackspace, the kernel tty line discipline rubs out your previouscharacter by printing (in the simple case

I recently read Things Every Hacker Once Knew , whichis really mostly about the somewhat less grander topic of ASCII,RS-232, and serial terminals ( via , and also ). Part ofthe article is a writeup of all of the ASCII control characters,covering their original purposes and what they're still used fortoday, if anything. It has this to say about CR (aka Ctrl-M, C \r ,decimal byte 13 (hex 0x0d, octal 0

A while back, Glyph wrote an article more or less decrying'tweetstorms' , whichare more or less multi-tweet sequences of remarks on Twitter andsuggested that they should be blog posts instead (he later added an important followup ). Onthe one hand I sort of agree with Glyph. Twitter doesn't make itvery nice to read long sequences of tweets, and when I wind uptrying to follow such things I generally wish I could get them ina blog post, even if it was just