Bup: Efficient file backup system based on the git packfile format - <AUTHOR> https://github.com/bup/bup <comment><USER2> Another backup possibility I currently use: ZFS on a backup server (not necessarily ZFS on the system that should be backed up), pull data with rsync on the backup host to a ZFS, after that make a snapshot for an "incremental backup".

So simplified it's like: rsync -avx remote:/etc /backup/ && zfs snapshot backup@`date`

With zfSnap ([https://github.com/graudeejs/zfSnap](https://github.com/graudeejs/zfSnap)) you can tell how long incremental backups/snapshots are kept, "rsync && zfSnap -d -a 1w backup"

You can take advantage of the /backup/.zfs/snapshot directory to access all snapshots, built-in compression and possible data deduplication.

If you also have ZFS on the remote host, you can use zfs send and zfs receive to transfer the snapshot directly to the backup server, instead of using rsync for the diff.

<comment><AUTHOR> rsync.net is an example of a host that does something like this (with daily snapshots)

        $> ssh rsyncnet ls .zfs/snapshot
        daily_2014-02-09
        daily_2014-02-10
        daily_2014-02-11
        daily_2014-02-12
        daily_2014-02-13
        daily_2014-02-14
        daily_2014-02-15

They allow you to customise the length of time for which these snapshots are kept, too (IIRC) (at the cost to you of the incremental extra storage)

<comment><USER3> rsync.net looks awesome, but it is just way too expensive for me.

<comment><USER4> You should email us and ask about the "new customer HN reader discount".

Also, note that 1TB accounts are 15c per GB, per month, and 10TB accounts are 7c per GB, per month - all with no traffic or usage costs.

This compares very favorably with S3 and blows the mozy pro pricing out of the water[1].

[1] [https://mozy.com/product/mozy/business](https://mozy.com/product/mozy/business)

</comment></comment></comment></comment><comment><USER5> Bup is lovely. I used it to back up my huge home folder and only switched away to rdiff-backup because (at the time) there was no support for deleting old revisions.

Is there any support for that? (Of course, for a large enough hard drive, it's not much of a problem...)

<comment><USER6> I wrote ddar, which is basically this but solves that particular problem, by using something other than the git packfile format.

[http://www.synctus.com/ddar](http://www.synctus.com/ddar) and [http://github.com/basak/ddar](http://github.com/basak/ddar)

It's recently been made available on Homebrew, too.

<comment><USER7> Nice. Could you add some description there how the deduplication works? I assume it uses rolling checksums to create chunk boundaries, just like bup?

<comment><USER6> > I assume it uses rolling checksums to create chunk boundaries, just like > bup?

That's right.

</comment></comment></comment></comment><comment><USER8> How do people who would use this kind of thing manage to have remote servers with terabytes of available disk space on them?

Anything is possible with money, of course, but how is this anything other than really expensive?

For example AWS S3 would be $235/month (that's $2,820/year!) for 3TB not even including any data-out transfer charges. Sure there are others that are cheaper but only marginally so.

Is this really what people are doing? Makes the commercial services sound really cheap.

<comment><USER9> My suggestion is to backup your cloud servers, which are expensive and redundant and have good uplink speeds, to home servers which are cheap and have good downlink speeds. You don't need your backup file server to be ultra- reliable or even up all the time, so the cheapest possible PC sitting on a home internet connection is a pretty good choice. That way, 3TB is just $150 or so plus your electricity, and it's not a per-month fee.

<comment><USER10> I'm curious as to how you would restore that much data quickly, from a home- uplink to the cloud?

<comment><USER11> You would send the hard drive via snail-mail to Amazon.

A mass restoration is expected to be rare, so it's okay for it to be a bit more expensive.

</comment></comment></comment></comment><comment><USER12> I hear about rdiff-backup, but I think its two main drawbacks are:

* on the webpage, there is no new release since 2009.

* has no de-duplication.

I was considering moving my 5+ years old rdiff-backup system to any of those new, promising programs:

* obnam [[http://liw.fi/obnam/](http://liw.fi/obnam/)]

* attic [[https://pythonhosted.org/Attic/](https://pythonhosted.org/Attic/)]

They both do automatic de-duplication, old backup deletion and remote encryption.

<comment><USER13> The original rdiff-backup author went on to create duplicity. Maybe a big part of the rdiff-backup community has followed him?

I'm using obnam now.

<comment><USER14> For a link, [http://duplicity.nongnu.org/](http://duplicity.nongnu.org/)

I backup locally using duplicity, then I ship those files off to Amazon Glacier using mt-aws.

[https://github.com/vsespb/mt-aws-glacier](https://github.com/vsespb/mt-aws- glacier)

</comment></comment></comment><comment><USER15> I'm assuming you're not the author. But just in case the author wanders by: How did you decide which parts to write in C?

<comment><USER9> It's not too hard actually. A line of python is roughly 80x slower than a line of C (no exaggeration). But a typical line of python does a lot more than a typical line of C. So things you can do with a "loose" loop (like once per 64k block) is usually ok in python. Things you have to do with a "tight" loop (like once per byte) need to be in C.

I once did a presentation about python performance optimization lessons from bup: [http://lanyrd.com/2011/pycodeconf/sghxk/](http://lanyrd.com/2011/pycodeconf/sghxk/)

And it's true, I'm not the most active maintainer anymore. The people who took over seem to be doing a pretty good job though.

<comment><AUTHOR> I'd be curious to know if your stance on PyPy has changed at all since 2011 (if indeed it's something that you've taken any new long looks at since) given their progress in that time.

I know that I would humbly submit at the least that my position has moved to believing that PyPy is a viable option for high-speed code (albeit in substantial part due to better interaction with C, nowadays).

</comment></comment></comment><comment><USER16> The most efficient backup system for operating systems I've used so far is 'tarsnap'. The only drawback is that restore is really slow.

<comment><AUTHOR> I love Tarsnap, but S3 storage costs aren't exactly brilliant. Figuring out exactly how you wish to store keys can also be another thought, upfront (albeit one that arises from the increased security that you get 'for free').

Alternately, CrashPlan and other consumer-style services have a bad habit of using very slow, heavy, world-slowing systemwide file update scanning. :/

Having said this, a discussion of the merits and flaws of Tarsnap and similar backup services is something I'm fairly certain I've seen lengthy discussions of on similar HN posts.

([https://news.ycombinator.com/item?id=5767116](https://news.ycombinator.com/item?id=5767116) is a good source for lots of that sort of discussion)

</comment></comment><comment><USER17> Not really closely related, but another solution that uses git infrastructure to back up large files is git-annex:

[https://git-annex.branchable.com/](https://git-annex.branchable.com/)

<comment><USER4> ... and there are some tangential benefits to using git-annex as well:

[http://rsync.net/products/git-annex- pricing.html](http://rsync.net/products/git-annex-pricing.html)

</comment></comment><comment><USER18> so, its 2014 and still people use homegrown variations of tar, rsync, git and whatnot. Or a half done solution like this, or an abandoned solution like box backup.

why on earth isnt there already a perfect cross platform open source backup program? :)

I know,i know..why dont i make one myself? because we dont need a nother half done solution :-b

<comment><USER5> Every "perfect cross platform open source program" had to start as a homegrown variation of tar, rsync, git, and whatnot. It's not like they fall out of the sky.

<comment><USER18> of course things dont come out of nothing, i just find it so odd that we have open source top quality OSes, monitoring systems, programming languages, ides, browsers, graphics suites, etc etc, but no backup ..

<comment><USER19> Not having a backup isn't a "pain point". Until you have a disaster. And disasters are infrequent enough ..

</comment></comment></comment></comment><comment><USER20> This is an outstanding project with great potential.

Killer for many commercial, overpriced services.

<comment><USER8> Where would you host the backups?

<comment><USER20> How about here:

[http://www.soyoustart.com/ca/en/offers.xml](http://www.soyoustart.com/ca/en/offers.xml)

</comment></comment></comment><comment><USER21> a 'backup system' that runs on python. how oxymoron.

<comment><USER22> Seriously. I write all my critical software in assembly so that my super-fast disks and networks aren't bottlenecked by unnecessary CPU instructions! Backup software always values speed over correctness!</comment></comment>


RFC 7239: Forwarded HTTP Extension - <AUTHOR> https://tools.ietf.org/html/rfc7239

<comment><AUTHOR> At last some standard for the variety described in [http://stackoverflow.com/a/16042648/253049](http://stackoverflow.com/a/16042648/253049)</comment>


Ask HN: Resources for creating a programming language - <AUTHOR>

I've had an ever growing desire to learn how to create my own programming language for some time now. Although I do know there are mature and more than capable languages available, I'd really love to learn how to do it and understand the processes involved.
I'm just wondering if any one had any suggestions for resources and literature, which would be useful and beneficial for learning this sort of stuff. Also, if you have any general advice or suggestions to help me a long the way, that'd be much appreciated too.
As I said, I know that it seems like I'm reinventing the wheel but this is my idea of fun and I'm sure most of you are the same (I'm assuming a lot there though)! Nothing beats getting home at night and having an all-night hacking session in my opinion!
Anyway, much thanks for taking notice and thanks in advance for any replies. Also, I apologise for any spelling, grammar and/or punctuation mistakes. I've been up all night playing around in C, so I guess it's understandable haha!<p>James. <comment><USER2> I recommend _Programming Language Pragmatics_ by Michael Scott as a good book to get you started: [http://www.amazon.com/Programming-Language-Pragmatics- Third-...](http://www.amazon.com/Programming-Language-Pragmatics-Third- Michael/dp/0123745144/)

<comment><AUTHOR> Much appreciated!

</comment></comment><comment><USER3> Are you looking for information on writing compilers as well, or just language design? If the former, I suggest Modern Compiler Implementation in (C|Java|ML) by Andrew Appel, as well as the de facto `Dragon Book' (Compilers, Principles, Techniques and Tools).

</comment><comment><USER4> <http://createyourproglang.com/></comment>


Show HN: Visualize Covid-19 cases with a WebGL Globe - <AUTHOR> https://github.com/anthonyftwang/webgl-globe-covid19 <comment><AUTHOR> Author here - built this visualization with two friends as a part of an ongoing project to accelerate and document local responses to COVID-19. A live version of the globe is up at: [https://earth.fightingcovid.net/#dashboard](https://earth.fightingcovid.net/#dashboard)

The globe has scripts to pull and process the latest data from the JHU CSSE repository - the code is open source, and personally I'd love to see if someone can improve on the balance between accuracy and viewability! (Linear scaling isn't really feasible here.)</comment>


SVG Lava Lamp - <AUTHOR> http://codepen.io/chrisgannon/pen/QjKXXe <comment><AUTHOR> The blog post about how is it made: [http://codepen.io/chrisgannon/post/how- to-make-an-svg-lava-l...](http://codepen.io/chrisgannon/post/how-to-make-an- svg-lava-lamp)

</comment><comment><USER2> I had no idea SVG filters were powerful enough to do things like that cool blobbing-together effect... in 3 lines of actual filter! (lines 8-10 of the html)

(I haven't actually followed along with building my own, nor do I know SVG, so apologies and let me know if that is not the bit which is doing the blobbing together)</comment>


A Letter from the Fed'd Hilsenrath to the American Consumer - <AUTHOR> http://blogs.wsj.com/economics/2015/06/02/grand-central-a-letter-to-stingy-american-consumers/

<comment><AUTHOR> I can't figure out if this is satire or not?

</comment><comment><USER2> satire or not ? Americans are broke ,the only segment with expendable income are the top percent , they will have to find a way to get the economy going themselves ,and it will take more then only supporting the Luxury economy.</comment>


Chinese database details 2.4mn influential people and how to press their buttons - <AUTHOR> https://www.theregister.com/2020/09/15/china_shenzhen_zhenhua_database/ <comment><USER2> Duplicate here: [https://news.ycombinator.com/item?id=24489165](https://news.ycombinator.com/item?id=24489165)</comment>


Ask HN: Best short article that explains SOPA/PIPA? - <AUTHOR>

It appears that few people outside the tech community understand why SOPA and PIPA are bad. Not even Wikipedia's "Learn more" page about their impending blackout explains what the fuss is about. What are the best short articles — the right length to share with our friends, family, and followers — that explain why SOPA and PIPA and why they are detrimental to the internet? <comment><USER2> I think it would be best to compose a short video that outlines all of the problems, as that's even more accessible to people. I've seen a few videos that are long, and a few videos that are inaccurate/vague, but no definitive explanation of the issue.

Here's the best video I've found so far: <http://www.everythingisaremix.info/protect-ip/></comment>


4WD vs. AWD. What's the Difference? - <AUTHOR> http://www.outsideonline.com/2096381/4wd-vs-awd-whats-difference <comment><USER3> Here are the key takeaways for me:

"Thanks to that differential between your axles, an AWD car will send your engine's power down the path of least resistance—the wheel with the least grip. Where a two-wheel drive car can only choose between two wheels, an AWD system looks for that least resistance across all four wheels."

"4WD works by locking the front and rear axles together, splitting torque 50:50 between them. This provides great traction, but a vehicle locked in 4WD cannot safely be operated on dry pavement because its front and rear axles are forced to rotate at the same speeds."

I remember being scared when I bought my first 4wd vehicle, a '91 Toyota pickup. I knew I shouldn't have the wheels locked in 4wd on dry pavement, and I was worried about going from snowy roads to dry pavement. When I moved on to an Outback (AWD, not 4wd) I wondered why I didn't have to worry about transitioning between slippery roads and dry pavement. Now I understand.

There's also a great video from 1937(!) that shows why we need differentials, and how they work. Here's a direct link to the video if you're going to skip the article:

[https://www.youtube.com/watch?v=yYAw79386WI](https://www.youtube.com/watch?v=yYAw79386WI)

<comment><USER4> And in the next paragraph "To counteract this [sending of power to the wheel of least resistance] , the better AWD cars are fitted with a center differential that contains a clutch or viscous drive unit. This splits torque front-to-rear, directing it away from the spinning wheel. "

So, a well engineered AWD system actually sends power _away_ from the slipping wheel(s) and towards the wheels with traction, which makes more sense.

<comment><USER5> That's right. A poorly-engineered 4WD system means you are stuck on a hill because _one_ wheel is on slippery wet leaves. AWD should mean you can get up that hill with _three_ wheels on slippery wet leaves, and one with grip. That's the simplest explanation.

I had an old Toyota Tercel 4WD station wagon and it was very difficult to steer sharply at low speed with 4WD engaged because of the lack of a differential. It would lurch and I had to press harder of the accelerator to get straightened out and pop it back into 2WD. It was my first car so I didn't know any better. Fun fact: In 4WD, you got an 'extra low' gear below 1st and that car could very nearly climb trees. The gear ratio was insane. No ground clearance but I used to scare the crap out of friends by going up very steep inclines in extra low gear with 4WD engaged. They would have to park their pickup trucks at the bottom of the hill and ride with me, and this caused them some embarrassment. Good times.

<comment><USER6> > That's right. A poorly-engineered 4WD system means you are stuck on a hill > because one wheel is on slippery wet leaves. AWD should mean you can get up > that hill with three wheels on slippery wet leaves, and one with grip. > That's the simplest explanation.

I think you just said the opposite of the guys above you while saying you agree. 4WD should not have a problem on slippery terrain.

<comment><USER7> It actually has nothing to do with 4WD or AWD, the article is poorly written and confuses several terms. At the surface 4WD is manually selected and AWD is 4WD all the time. Thats it they are the same thing, it's just 4WD means you opt to put the vehicle in 4WD.

The term the are talking about when traction is applied to the wheel with the most binding to the ground and away from the one that has the least traction is called a Limited Slip Differential and by virtue of the slipping of the low traction wheel it will spool the high traction wheel and bind it transferring torque to it. This can also be done by what is called a locker, either electronic or manual but manual lockers can be dangerous at high speed if you are not used to their manor. You generally only see manual lockers and welded differentials in offroad trucks. Limited Slip differentials and electronic lockers are available in both 4WD and AWD vehicles.

The term they are talking about to apply power to both the front and rear wheels is not a differential but rather a transfer case and it is not always at a 50:50 ration man times they run 60:40 or 70:30. Both 4WD and AWD have a transfer case, 4WD's allow you to select whether they are engaged or not.

The term they are talking about when they talk about adjusting power front to back is called a Traction Control Unit and is handled by a Body Control Module that may or may not also communicate with the Engine Control Unit or the Transmission Control Unit to defuel or detorque the powertrain, as well as adjust torque via electronic lockers in the differential to the wheels that need it and away from the ones that do not. As well as engage or disengage front and back axles via the transfer case. Many newer AWD systems have this but it is also available in most newer 4WD vehicles.

TLDR is 4WD and AWD can be virtually identical depending on the subsystems but the article confuses a lot of those subsystems as being unique to one or the other. Though the upper end of 4wd's have more "hardcore" options not generally found or offered in AWD vehicles.

<comment><USER8> I found the article very good explaining the basics and history of awd vs 4wd. What you explain is the status of today's 4wd vs awd, where indeed the features in awd vs 4wd cars can overlap a lot and because of the big variety of implementations quite hard to understand by regular Joe

</comment></comment></comment></comment></comment></comment><comment><USER9> There are lots of variations on this theme. There are off-road differentials which limit the speed difference between the output shafts to a fixed maximum ratio, usually in the 2:1 to 4:1 range.

It's possible to do some or all of this in software. Tesla has an ordinary open differential but will apply the brake on an overspeeding wheel. Tesla's all wheel drive system has a separate motor for the front and rear wheels. Power distribution between the two during acceleration is mostly equal, but once speed stabilizes, the rear powertrain takes most of the load. Off-road slip handling doesn't seem to be well documented, but Tesla cars aren't intended for off-roading.

The most advanced systems are seen on locomotives. Modern heavy locomotives (GE Evolution series) use three-phase AC synchronous motors driven by IGBT inverters from power from a Diesel generator. Each axle has its own motor. All axles are normally locked together electronically by the control software, so no wheel can slip ahead of the others. Locomotives can be cabled together so that the axles on multiple locomotives synchronize. Now that's all-wheel drive. This is a huge win when starting a heavy freight train. Locomotive axles that are slipping provide little pulling power and damage the tires and rails.

<comment><USER10> "It's possible to do some or all of this in software. Tesla has an ordinary open differential but will apply the brake on an overspeeding wheel. Tesla's all wheel drive system has a separate motor for the front and rear wheels. Power distribution between the two during acceleration is mostly equal, but once speed stabilizes, the rear powertrain takes most of the load. Off-road slip handling doesn't seem to be well documented, but Tesla cars aren't intended for off-roading."

I don't think about this a lot, but I _assume_ that all of the interesting ways to distribute power from a single engine to 1-4 wheels are, all of them, inferior to having a dedicated motor for each.

That is, I _assume_ that no matter how fancy you made your differentials, two motors is better than one and four motors (one for each wheel) is better than two (all else being equal).

Is that correct ? Or is there some scenario(s) wherein mechanical distribution of torque (with differentials) is superior to (again, all else being equal) a dedicated motor on that wheel ?

...

If I try to answer my own question, all I can come up with is:

1\. If you have a motor for each wheel, the max output on that wheel is the max output of that motor, and theoretically, you can distribute _more than 1 /4_ of the single engine to that wheel with differentials, so ... maybe that's a very big deal ? Do 4WD vehicles often send 70-80-90% of output to one wheel ?

2\. Sending power to a specific wheel via the path of least resistance takes zero time - it's instantaneous - whereas deciding what to do with each of the four wheels (in software, presumably) might have a lag ... although that sort of breaks my "all else being equal" tag, above ...

<comment><USER11> One more thing to think about, on this line of questioning, is efficiency in "normal" driving situations.

If you're driving in a straight line, with good traction on all wheels, will a single larger motor be more efficient than two smaller ones on each wheel? For many people, I think that's 99% of their driving, so it makes sense to optimize. Especially on electric vehicles, where increasing battery capacity is much harder than just adding an extra gas can.

Maybe in that case the complexity of AWD/4WD/Traction control makes sense in that case.

<comment><USER9> One motor per wheel, in the wheel, is an old idea. It's been used most notably on LeTourneau heavy equipment. The usual problem is too much unspring weight, not a problem for giant earthmovers but bad for fast cars.

Michelin was pushing it for cars, with their "Active Wheel" concept, from about 2003 to 2012.[1] That seems to have disappeared. Siemens has demoed a motor-in-wheel unit, and Volvo and Nissan have fooled around with this. Protean, in Shanghai, is trying to sell their wheel motor. There are others. Nobody has shipped production cars yet, though.

[1] [https://news.ycombinator.com/item?id=383607](https://news.ycombinator.com/item?id=383607)

<comment><USER10> "One motor per wheel, in the wheel, is an old idea. It's been used most notably on LeTourneau heavy equipment. The usual problem is too much unspring weight, not a problem for giant earthmovers but bad for fast cars."

hmmm ... I wasn't thinking about motors _in_ the wheel, although I am familiar with that concept.

I was thinking about a more pedestrian motor per wheel configuration wherein the motor is just behind the spring ... and is thus, sprung weight ... is there even space for that ?

</comment></comment></comment></comment></comment><comment><USER12> This definition is broken.

You have 4WD if you have 4 driven wheels (and unless you count the spare, that's all my wheels). Then, you can have a multitude of differential configurations on the 3 differentials (open, lsd, locker, diff-less viscous clutch, diff-less locker).

A Jeep WK uses a locking differential center, and electric engaging LSD's front and rear. By that article, the car is AWD on road, and sorta 4WD when off. The Jeep WJ is either controlled by a viscous clutch (Quadra-Drive), or has manually selectable 2WD, 4WD open ("AWD") and 4WD locked ("4WD") modes. A 98 Ford Explorer pulses an electric clutch to go between 2WD and 4WD locked. These cars all behave very differently both on and off road, and they don't fit well in the authors categories.

If you're buying or owning a car that drives all wheels, the only useful information is the diffs. Labels like "4x4", "4WD", "AWD", "Quadra-Trac", and "Quattro" mean nothing.

Most new 4WD's use open diffs with electrically controlled lockers or LSD's, as that gives the best combined on/offroad experience. Permanent LSD's/viscous clutches (Jeep WJ, for example) is a bit more responsive in surprise low- traction conditions, but it eats your tires when you make tight u-turns, as the turn will progressively engage a complete diff lock. Center lock without diff works like a regular 2WD until you lock, but remember that if you have ANY type of locker on ANY axle (not LSD), then engaging in high traction conditions might snap your axels in a very loud and explosive manner, even if you think you're driving straight.

</comment><comment><USER13> In real life, in most situations, ground clearance, good tires, traction control and ABS make more difference than driving all four wheels, most of the time. Personally, I'm more concerned with stopping than starting, and that's where ABS and good tires matter and what kind of transmission you have doesn't.

This is a sales pitch video, but it is interesting to illustrate the differences in AWD approaches, with different vehicles on rollers: [https://www.youtube.com/watch?v=9cuZYTQLfA0](https://www.youtube.com/watch?v=9cuZYTQLfA0)

I spent a lot of time looking at this several years ago when my family was planning on taking a vacation to the Outer Banks of North Carolina where you have to drive on the sand. We ended up renting a Ford Explorer that had a "sand mode" in it's electronically controlled awd setup. Worked great.

<comment><USER14> Something I've learned is that snow tires make a big difference during the winter, and I've read that they make a bigger difference than AWD.

<comment><USER15> Have been a driver for only 2 years but I can confirm that. I live in Eastern Europe where we tend to have at least one or two snow storms per winter, and, indeed, having winter tires and ABS makes a ton of difference, even on a 1.4-liter FWD vehicle like mine.

And, even more important, you have to keep a level head when you see that there's snow on the road and not try to do anything crazy, like making sudden left or right wheel movements. Also try to keep a safe distance from the vehicle in front of you, and, before you venture on a trip outside of the city, just check the weather forecasts: if there's a "red code" storm announced you'd better postpone your journey, only a tank can get you out from something like this: [https://www.youtube.com/watch?v=Frf2lV77fl0](https://www.youtube.com/watch?v=Frf2lV77fl0)

<comment><USER16> Bah, you can still see the road in that video. :-)Not to one-up you, but rather to point out what's possible, your video is a not-uncommon regular winter storm in the midwestern U. S. I grew up driving 2WD RWD vehicles in that stuff, usually got home just fine. I did land my parent's full-sized van in the ditch once. Should have put 25kg bags of salt in the back end to add weight, but might have used said for the water softener, don't recall.

So you don't _need_ 4WD (let alone a tank) if you have some sense. Which is why a lot of people buy 4WD vehicles, I guess.

</comment></comment></comment></comment><comment><USER17> Great! Finally somebody explained this to me, I thought it was just a marketing term related to different patents of similar ideas.

I was puzzled by this as I was stopped by a ranger coming out of Waipio Valley on Hawai'i, where there was a sign "4WD only" and my rental car had AWD. I thought they were the same, just different names, so I argued with the ranger that I do in fact have 4WD, which is in my case just called AWD and in other cases 4x4 as well. Well, he was still pretty upset but the "I am a European and we have different cars" finally disarmed him...

<comment><USER18> Generally a sign saying you need 4wd in the US really means you need a lot of ground clearance. Your car probably would have high-centered, that is stuck resting on the middle of the car with the tires in the air.

The annoyed ranger was probably just tired of pulling stuck tourists out.

<comment><USER19> Normally I would 2nd this, but it does not apply on this particular 4x4 road. It really sucks when opposing traffic appears as it's barely wide enough for 1 vehicle in most parts:

 _The road gains 800 vertical feet (243.84 m) in 0.6 miles (0.9 km) at a 25% average grade, with steeper grades in sections. This is a paved public road but it is open only to 4 wheel drive vehicles. It is the steepest road of its length in the United States._

[https://en.wikipedia.org/wiki/Waipio_Valley](https://en.wikipedia.org/wiki/Waipio_Valley)

<comment><USER20> That doesn't seem that bad for normal traffic, conditions permitting - <USER2> the steeper gradients are markedly so. I'm sure they have their reasons for 4wd only though - picking too many tourists out of the ditches or whatever.

There's quite a few roads in the UK with 1:4 gradient, and one just down the road from me at 1:3 whose only restriction is no trucks and vans. Going downhill on the motorbike makes it feel like you're falling off! :)

[https://en.wikipedia.org/wiki/Hardknott_Pass](https://en.wikipedia.org/wiki/Hardknott_Pass)

<comment><USER21> Here in New Zealand we lay claim to the steepest street in the world at 1:2.86 gradient [https://en.wikipedia.org/wiki/Baldwin_Street](https://en.wikipedia.org/wiki/Baldwin_Street).

There's an annual charity event that involves the rolling of over 30,000 Jaffas (spherical confectionery-coated chocolate confectionery) down the hill.

<comment><USER22> How have I not heard of this event? Sounds similar to (and less dangerous than) cheese rolling.

</comment></comment></comment></comment></comment></comment><comment><USER23> This article is good but goes overboard in explanation. AWD and 4wd by all accounts are just buzz words for having front and rear differentials. In actual use, a 4x4 (a term I mean to refer to both 4x4s and awds as its just a buzz word) has three differentials. A center diff splits power from the transmission out to the other diffs, which split power to the wheels. There are three general types of diffs, whether centered or front or back:

Open (just gears, sends power the the least resistant path)

Locked (a spindle connects the input directly to the output and all three spin proportionally)

Posi (multiple ways of actuating this, can be viscous clutch, electric or air powered actuation, or mecanical geared torsion style - regardless the point is to keep power at all wheels, some with variable speeds allowing for turns - others act like a spindle)

Most "awd" cars have a open gear in all three diffs. My jeep has a spindle in the front and center and an air locker in the rear (not the stock design). My old BMW 325ix has a viscous clutch in the center and in the back, and open in the front. My dad's audi has open gears all around and uses the brakes to actuate were the power is delivered. At the end of the day tho, its three differentials.

<comment><USER24> There is a non-buzzword practical difference; one system cannot be driven on dry pavement (part-time 4x4). One system can be driven on dry pavement (full- time AWD).

</comment></comment><comment><USER25> It'll be interesting to see what happens when off-road vehicles start becoming electrified. Separate front/rear motors eliminate the need for that middle differential or transfer case, and if we eventually transition to a separate motor for each wheel, we'll be rid of all of the differentials and have much better ground clearance as well as better traction.

For now, I suppose electric trucks/jeeps are more affected by "range anxiety" than daily-driver sedans, since people tend to imagine themselves driving to some remote location when they buy them. But as technology improves, I would love to see something like a modern reincarnation of a 1960's era CJ-5 (but with better safety features) -- simple, easy to modify, nothing that doesn't need to be there, and reasonably priced.

<comment><USER26> The army gets interested in electric vehicles for troop transport _because_ of their range. It happens that 1. A hybrid can basically provide the same range, 2. A hybrid can regenerate energy when the driver slows down, providing much better range, and 3. They can approach a target in silence for the last 15 minutes, thanks to the electric motor.

The drawback is, they struggle with on-field repairs.

</comment></comment><comment><USER27> The video from the 30s was fascinating. It gave a perfect progression of complexity while explaining the concept of a differential. I'd like to see more of those kind of videos (from now our from clear back then).

<comment><USER28> You might like Sheaffer's "The Twenty-Six Old Characters", c. 1947. It touches a bit on the progression of language, but it's really about writing instruments. It culminates in explaining Sheaffer's "Snorkel" mechanism, which was probably the most novel and complex pen system ever designed. I have several and love them :)

[https://youtu.be/1xUDehNvbrE](https://youtu.be/1xUDehNvbrE)

</comment></comment><comment><USER29> The performance of either system is completely dominated by the traction aid at the axles. The article is otherwise good because most AWD vs 4WD stuff completely igores the axles (because it's a heck of a lot to explain if you really want to compare the various systems) but kinda misses the main point.

Open, bad traction control (cuts throttle, applies a little brake), good traction control (all brake no throttle), the many varieties of LSDs, automatic lockers, manual lockers, Lincoln lockers and spools all have a huge affect on traction.

Lincoln lock the diffs of any AWD crossover, screw with some wiring so it's full time and you'll have something that can out wheel a $50k Jeep but trades off a tiny bit of grocery getting capability.

<comment><USER10> Thank you for introducing me to the concept of lincoln-locking a differential. Appreciated.

</comment></comment><comment><USER30> 4WD/AWD are almost never necessary in USA and Europe today, to the extent that, if you buy 4WD/AWD you're likely suboptimizing and even taking a risk (for your drivers who aren't familiar with the quirks of 4WD/AWD). As Saab has shown for decades, FWD will get you almost almost anywhere a 4WD/AWD will in bad weather.

But sales of 4WD and AWD cars have been a boondoggle for the auto manufacturers. Cost, complexity and maintenance are significantly higher: often you must "fiddle" with them, woe to you should you damage them due to bad judgement. They reduce mileage, increase car weight, and reduce reliability.

I prefer a RWD car for most driving, since it handles better and I'm never climbing bare hills or plunging through swamps, but I was raised on oversteering go-karts.

"All Wheel Drive Does Not Make You Safer": [http://www.mrmoneymustache.com/2014/12/01/all-wheel-drive- do...](http://www.mrmoneymustache.com/2014/12/01/all-wheel-drive-does-not- make-you-safer/)

"The Myth of the All-Powerful All-Wheel Drive:" [http://www.popularmechanics.com/cars/a3091/the-myth-of- the-a...](http://www.popularmechanics.com/cars/a3091/the-myth-of-the-all- powerful-all-wheel-drive-15202862/)

4WD/AWD safety - Is 4WD/AWD safer on snow and ice? [http://www.4x4abc.com/jeep101/safe.html](http://www.4x4abc.com/jeep101/safe.html)

<comment><USER31> This is absolutely false.

I live in Utah where we regularly get snow measuring feet deep. Driving up the canyon to go skiing, or doing anything in the state during winter or in all the wilderness, it is required by law to have 4WD.

All over the west there are roads that are impassable without 4WD. I use it all the time.

<comment><USER32> The parent and other people commenting about trashing 4WD systems are from Europe. I'm not sure if there are as many remote places in Europe anymore especially compared to Utah.

I go trout fishing a lot in North Georgia and many places I go would be accessible in a small fwd car. In fact if people saw you driving an incapable vehicle they would stop and warm you about proceeding further.

<comment><USER33> Try Norway for size. I live in a rural area and the everyday car is a Land Cruiser - in summer, just about anything goes - but come winter, and big, studded tyres, low range and diff locks all over (well, center and rear in my case) are what gets you from A to B and back.

Anecdotal evidence makes me claim that electronic traction control systems are excellent, but still no match for good ol' manual systems - probably in part because the automagic systems are easily taken for granted, making drivers forget what icy conditions are like - and using the electronic systems to drive faster, not safer.

<comment><USER24> Electronic systems also work best on the road. The looser conditions get, the worse they often perform.

</comment></comment></comment></comment></comment><comment><USER34> The problem of the outer wheel going farther during a turn also occurs with trains, and trains do not have differentials to let the wheels have different angular velocity. On a train, the inner and outer wheels have the same angular velocity regardless of turns.

How trains accomplish this is interesting: [http://jalopnik.com/5820296/how- trains-make-turns-without-di...](http://jalopnik.com/5820296/how-trains-make- turns-without-differentials)

I'm linking to Jalopnik, which embeds Richard Feynman's video on train turning, rather than directly to the video because there are some interesting comments on the site. In particular, see the comment from railroad employee "Gonemad" about how they have a system that automatically greases the wheels before turns, which seems rather counterintuitive at first.

</comment><comment><USER35> Kind of an odd post to see on hacker news. As somewhat of a car buff my take away is that this article gives an adequate high level explanation but leaves out a lot of useful details, especially to anyone evaluating 4WD/AWD vehicles, like the tremendous differences between modern AWD systems.

</comment><comment><USER36> One thing that this article only touches on briefly is that more and more AWD systems today are just open differentials plus the TCS instead of using more expensive and heavier limited slip differentials. These modern systems are lighter and cheaper but they have disadvantages; not least of which is that using the brakes to force power to move around wastes torque, and it's only going to be as good as the sensors. If the ABS/TCS system has any issues your AWD goes out too.

I've owned cars with every type of AWD system (Audi, Subaru and currently a Honda) and day to day they all work just as well. Given that, I suppose the manufacturers are ultimately right to go with the cheaper and weight saving system.

<comment><USER29> The brake based system is great if the traction control is programmed for "get me up this snowbank" and not "prevent me from being an idiot"

There was an episode of Dirt Every Day where Fred and co. took a Jeep Renegade(?), or whichever the small one is, off-roading there were some great scenes of the traction control in action. Basically by spinning the dial to rocks the traction control knows to use ABS to approximate how one would work the brakes with a torsen.

</comment></comment><comment><USER37> The newer Jeeps actually have both! It's an improvement over AWD and they call it "Active Drive".

It engages/disengages the center differential (4WD) as needed automatically, but can also transfer power to be greater in the front or rear as desired - with presets for 60/40 and 40/60 rear/front power. (Sport mode, Mud/Snow)

It's also got traction control w/ ABS, and it uses the brake locking differential technique on each axle as the article describes in advanced AWD systems.

Of course they have different variations, one of which also has locking differentials on top of everything else.

It's amazing to drive. It's all fully automatic too.

</comment><comment><USER38> No mention of the "Detroit Locker", IMHO one of the more clever automatic- locking differential designs --- it uses a pair of dog clutches which are normally engaged, one for each side, and the wheel that spins faster is allowed to. It's self-contained and requires no additional controls, just like a regular differential. I think the only reasons why they didn't become more popular are due to their cost and the noise they make --- a very noticeable clunking on tight turns as the outer wheel tries to go faster and unlocks, then locks again as the vehicle straightens out.

[http://www.eaton.com/Eaton/ProductsServices/Vehicle/Differen...](http://www.eaton.com/Eaton/ProductsServices/Vehicle/Differentials/detroit- locker/index.htm)

Having driven a "4WD" with all _three_ differentials of this type, I now wonder if it would be classified as 4WD or AWD.

<comment><USER39> Detroit locker is effective, but I wouldn't really call it clever. For that I think of Torsen, the Torque Sensing differential that uses planetary gears. The problem with the Detroit is primarily noise, as you mention. The problem with Torsen is that it doesn't work in the presence of near 0 traction on one of the outputs, so people will drag the hand brake in that case.

</comment></comment><comment><USER40> Of course, this only matters when you are driving four wheels with one engine. Now that we're going electric you can have one engine per wheel, or one front engine and one back engine and use ABS across single axles. It's kind of amazing how much progress we have made with simple internal combustion engines.

</comment><comment><USER39> I don't really buy this article. The terms AWD and 4WD don't really define a set of functions, but the article says they do then waves hands at all the exceptions.

Really, from what I've seen, current usage is AWD is a 4WD system marketed for on road use, and 4WD is an AWD system targeted to off road use. The biggest indicator seems to be if a vehicle has a low range transfer case, it will likely be marketed as 4WD. Also, if it is marketed as 4WD, _HOPEFULLY_ it will have under body armor.

Remember, not all AWD/4WD systems are equal. Last winter our neighbor's Subaru Impreza with Symmetric AWD (which Subaru claims is super good) couldn't make it up a small incline by our houses. Both my Audi and Land Cruiser on all season tires had no problem.

<comment><USER41> I owned a WRX that I never got stuck in snow. I once came up to a hill with a Sabb and Civic both spinning; and a semi-truck that couldn't really move when they were in the way. I had to wait for both of them to give up, left off my clutch, and crawled up the hill.

</comment></comment><comment><USER42> There's a lot of blurring and different labeling of 4WD systems based on the market segment.

Generally it's more helpful to think of 4WD/AWD as fitting into three categories:

1: A system with a _transfer case_ that predominantly drives one axle (almost always the rear, and almost always labeled "4WD"). This is your typical pickup truck 4wd system. When it is engaged, the two axles are locked together and may as well be welded and they'll turn at the same speed.

2: A system with a _center differential_ , in which both axles are driven but may turn at different speeds (Almost always labeled AWD). The differential may allow full or progressive locking and/or torque vectoring. It's rare to find one of these that can fully lock (Subaru WRX STI is the only one I can think of), but it's common to see ones that favor one axle (Audi, BMW, Mercedes) or that can partially lock in response to slipping of one axle (often with the brand name Torsen). These are almost always found on passenger cars, and with few exceptions they're found on cars with longitudinally mounted engines (Mitsubishi EVO being the only transverse layout car with a center diff I can think of), that means they're usually found on higher end cars that are based on front-engine rear-wheel drive models.

3: A system with a _power-take-off unit_ (often brand name Haldex), in which one axle is driven and a clutch pack can partially or fully engage the other axle. (this is often labeled AWD when put on a passenger car, and 4WD when placed on a "truck") The axles can operate at different speeds but can also fully lock in the way a transfer case can. Typically you find these on "AWD" cars that are based on transverse-mounted front-drive models as it's easier to add such a system and get partial engagement of the rear axle, but you'll also find them on performance AWD applications based on rear-drive mid/rear-engine models like Porsche 911s or the Buggatti Veyron. You'll even find it labeled as a 4WD system on "trucks" like Honda Ridgeline or Pilot, or on the new Ford Raptor. These tend to operate more like an automatic transfer case, as the only way to partially engage the secondary axle is to slip the clutch, which you don't want to do 100% of the time. (Ford actually calls this system a transfer case on the Raptor).

You'll see all sorts of spurious claims about systems "sending 100% of the torque to the rear axle" (often just means that the system can fully lock, and 100% torque to the rears means the fronts are in the air). You'll also see things like "rear biased", which sometimes means you have a center differential that overdrives the rear axle by default, which is great, but is often misleadingly applied to PTO/Haldex systems where the rears are also overdriven, but only during the rare times when the system is engaged.

Basically if you're looking for traction in low speed settings where you might not have grip at all on one axle, like offroading or being stuck in the snow, you want as many of your axles locked as possible, which technically you can get with any of these systems, but is usually seen on transfer cases or haldex/PTO systems.

If you're driving quickly on pavement with some traction, you usually want something more like a center differential, preferably one that can partially or entirely lock when you lose some grip at one end.

<comment><USER43> Right. I've got a Golf R with Haldex; it allows 30+mpg under cruising conditions but can "lock 100%" in the sense that the fronts and rears are locked together. It's created a lot of forum wars because some people read the marketing materials saying "100% of torque to the rear wheels" or "max 50/50 split" and don't understand the difference. If it's fully locked, on dry pavement, of course you're getting 50/50\. If the front wheels are on a magic 0 friction surface, of course, all of your torque is going to the rears because the fronts have nothing to grip on, but they're all spinning at the same speed (theoretically).

<comment><USER42> Great car, and yeah, it's even more fun when you explain that the Haldex systems often pull off either the left or right half shaft...

</comment></comment></comment><comment><USER44> I wonder why car manufacturers still use direct force transmission with hugely complex (and in case of ignoring the instructions, outright dangerous) like 4WD/AWD instead of diesel-electric or diesel-hydraulic systems like on locomotives.

A computer could instantly shift torque with both of the hybrid solutions, you wouldn't need a clutch or a gearbox any more, not to mention cheap all-wheel- drive including the trailer in trucks. And a fuel-electric drivetrain could easily plug in a battery or supercaps for braking energy recuperation, and the fuel engine could always run at peak efficiency/exhaust gas condition...

<comment><USER45> The Jaguar C-X75 [1] concept car uses exactly this idea, it uses a tiny and very efficient jet engine that is charging the batteries. Very neat idea.

1: [https://en.wikipedia.org/wiki/Jaguar_C-X75](https://en.wikipedia.org/wiki/Jaguar_C-X75)

<comment><USER44> What the f..k. Thanks for that link, a jet engine?! That's crazy. But it's the "awesome" kind of crazy.

And the CO2 values... wow, how is that possible? Burning a defined amount of fuel should always produce the same amount of CO2?

<comment><USER46> Gas turbines operate efficiently at constant output, which a hybrid-drive system with storage can manage. They only need to kick out enough power, on average, to keep the storage system fully charged. Batteries and eletric motors can handle both high-demand accelleration, and regenerative braking. Since the turbines are running at a very constant range, and can be rated to average out power load inclusive of idle times, they can be designed for optimum efficiency within that range. Or that's the theory.

There've been other gas-turbine automobiles, including some prototypes built in the 1960s. A friend of mine test drove one, claimed it could lay a patch (spin the tires) at highway speeds. Though my understanding is that in direct- drive applications (such as that), turbine lag is an issue.

The exhaust also runs quite hot, and turbines typically emit a lot of NOx (nitrous oxides), what you get when you run atmospheric nitrogen through a high-temperature field.

Much anecdata here, apply salt liberally.

<comment><USER47> For anyone interested in turbines and cars, there's a delightful episode of Jay Leno's Garage about a Chrysler turbine car:

[https://www.youtube.com/watch?v=b2A5ijU3Ivs](https://www.youtube.com/watch?v=b2A5ijU3Ivs)

He talks extensively about how it works, what it's like to drive, and the various difficulties that resulted in it never entering mass production.

<comment><USER48> It sounded like a gigantic loud vacuum cleaner even just idling, and gave the impression of straining mightily to achieve even mild acceleration. Fuel consumption was TERRIBLE.

</comment></comment></comment></comment></comment></comment><comment><USER49> Alright, time to bust a myth. As an AWD owner, every time I have a tire issue, they tell me I need to replace all 4 even if the others are good ... because AWD. "Won't someone think of the tires ... the tires need to to be the same size so they can rotate at the same rate."

Clearly, with AWD the car is designed to allow wheels to rotate at different rates (hence the diffs). Otherwise you would't be able to make a turn. Once you dispel that myth, they then tell you to replace the pair ...

Why do dealerships, repair shops and tire places keep insisting on replacing all 4? ... good for tire sales I guess.

<comment><USER50> The reasoning I've heard is that your differential will get worn out.

<comment><USER49> That makes no sense to me. Unless you are driving in straight lines, the 4 wheels will always be turning at different rates (and consequently, the front and back axles will be rotating at different rates).

</comment></comment></comment><comment><USER51> Subaru's higher end AWD system has separate output shafts from the engine for the front and the rear, with electronically-controlled clutches modifying the torque. Default is 60/40 front biased, but it can send 100% of the torque to either end of the car. Excellent performance with no manual mode switching needed, also manages good fuel economy at the same time. Best system in the business.

<comment><USER52> However, if you don't have locking differentials you can still get into the situation where one wheel slips and the wheel that grips doesn't get any power - as shown by the Subaru getting stuck on the hill in this video: [https://youtu.be/hrdb_UVTa20?t=543](https://youtu.be/hrdb_UVTa20?t=543)

<comment><USER53> There is a trick that seems idiotic but if you have a mechanical hand brake you can stop the wheel from free spinning. I'm not sure how well it would work for a front wheel, maybe you could hold the brake slightly while on the throttle. Again, seems ass backwards but if you think about what you're doing you're basically "locking" the open diff.

</comment></comment></comment><comment><USER54> All this talk of traction and moving forward is great but one of the most important things to remember about 4WD or AWD especially in snow and ice is that is doesn't enhance your ability to brake. It is easy to feel fearless being able to accelerate on a slippery road but a bummer to discover you can't stop (yes, I get that engine braking plays a role...).

<comment><USER55> which is precisely why tyre choice is more or less equally important on your little buzz box as it is your high end sports car.

</comment></comment><comment><USER56> Wow, early cars connected the engine to only one wheel, to completely avoid issues of differential.

(According to the cool old video linked in the article.)

<comment><USER57> My cousin had a firebird, I think a '67, that (seemingly?) had 1wd. He could do donuts that left one trail.

Not sure if by design or some kind of failure...

</comment></comment><comment><USER58> And then there are the dual motor cars like Teslas and Toyotas that have no mechanical link between front and rear axle at all. As you'd imagine, this can allow for a heck of a lot of flexibility.

</comment><comment><USER59> You don't need 4 tires to get traction. Just need a 2 cylinder John Deere! [https://youtu.be/sZBjNKhcWtY](https://youtu.be/sZBjNKhcWtY)

</comment><comment><USER60> Can't we do away with all the complexity by just having 4 electric motors and a gas engine as a generator? Then each wheel can be computer controlled independently.

</comment><comment><USER61> In my Jeep Wrangler, I can instantly tell I forgot to switch from 4WD to 2WD as I turn onto pavement from a dirt road.

</comment><comment><USER62> >Torque goes to whichever of the four wheels has the least grip.

That should be the tire with the most grip. If torque goes to the wheel where the tire on it has the least grip the tire still has no traction torque doesn't make grip appear out of nowhere.

In four-wheel or all-wheel drive one wheel where a tire has no grip the other three wheel with tire that have grip move the vehicle isn't that the entire point of 4WD and AWD?

<comment><USER63> Mechanically a drivetrain has no means of differentiating between a tire that is slipping vs a tire at that's on the outside of a turn. A 4wd car with three open differentials will absolutely send all of the engine power to one slipping wheel.

The author is describing the tricks used to get around that fact. Namely locking differentials or limited slip differentials. The end result is a fraction of the torque makes it to other Wheels depending on the design of the drivetrain. The author spent a lot of time on locking differentials when those are rare. Limited slip differentials are more common. Most awd cars will have a LSD in the center diff.

There are torsen diffs which do what you describe but they are rare.

<comment><USER42> Even a torsen diff, or similar helical/gear type limited slip diffs are "torque multiplying", they need a load on one wheel in order to send the "multiplied" load to the wheel with traction. Modern stability/traction systems equipped with helical diffs will apply the brake to the "free" wheel in order to provide a load to the mechanical diff. You can also apply the brakes yourself if you have a torsen diff but no electronics.

A clutch-based diff or some other type of locking diff would otherwise be required to solve the "wheel in the air" problem without applying an artificial load to the free wheel.

<comment><USER55> There is at least one mechanical design which (claims to?) solve this problem, Wavetrac.

Don't want to embarrass myself trying to explain it, so click "how it works" on this page: [http://www.wavetrac.net/technical.htm](http://www.wavetrac.net/technical.htm)

</comment></comment></comment></comment><comment><USER64> AWD should be redefined as Automated Wheel Drive or Auto all Wheel Drive.

</comment><comment><USER65> This article falsely assumes certain differential setups based on 4WD or AWD.

</comment><comment><USER66> Great explanation

</comment><comment><USER67> Jesus what a SHIT article It gets so many things wrong I don't even know where to start.

Why is this garbage spam on Hacker News?

<comment><USER68> I always find it suspect when people claim that something is so bad that they cannot find a single concrete thing to criticise it on.

I'd suggest you start with the thing you believe they got "most wrong" and go from there. Otherwise this comment seems to lack substance.

<comment><USER67> Oh there's an absurd amount of concrete things to criticize about this article.

I just don't see why I should be giving free editorial services and in effect encouraging what I consider to be blog spam infecting a site I love.

<comment><USER68> Then your comment isn't constructive.

This is a discussion site, meaning we discuss things, telling us a potential problem with the source is a great discussion topic. Taking unqualified potshots at the article doesn't provide a jump-off point to any discuss worthwhile.</comment></comment></comment></comment>


Reversing the Smarter Coffee Machine Protocol to Make Coffee Using the Terminal - <AUTHOR> https://www.evilsocket.net/2016/10/09/IoCOFFEE-Reversing-the-Smarter-Coffee-IoT-machine-protocol-to-make-coffee-using-terminal/#.V_pNmOrep1Y.hackernews <comment><USER2> Good work, although already done: [http://adenforshaw.com/smarter-coffee- machine-raspberry-pi-i...](http://adenforshaw.com/smarter-coffee-machine- raspberry-pi-iot-coffeetime/)

<comment><AUTHOR> ooooops, I didn't see that ... anyway, mine looks more complete so it wasn't 100% wasted time :D

<comment><USER2> An afternoon spent reverse engineering is never wasted time...

<comment><AUTHOR> absolutely! :D</comment></comment></comment></comment>


Rick and Morty writer's room - <AUTHOR> http://orangemind.io/post/rick-and-morty-writers-room <comment><AUTHOR> I was curious about how writing process on Rick and Morty works, and have collected some cool information.

I know it's a bit offtopic for HN, but I think you guys will find it interesting.</comment>


iOS-simulator-GIF: A bash script to record iOS Simulator GIFs - <AUTHOR> Hi HN! I created a simple bash script to record iOS Simulator gifs for macOS. That's something we're using quite a lot in my current project and I took the chance to try and learn a bit more of bash programming. Let me know what you think<p>https://github.com/fjcaetano/ios-simulator-gif <comment><AUTHOR> [https://github.com/fjcaetano/ios-simulator- gif](https://github.com/fjcaetano/ios-simulator-gif)

Clickable link ^</comment>