Wikipedia:Reference desk/Archives/Computing/2011 June 29

Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 29

Playing Downloaded .cue & .flac files

I have downloaded some music (my first time) and find I have a .cue and a .flac file for the piece I downloaded. What needs to be done for one or both of these to become a playable sound-file on my Windows media player? Can anyone help a musical newbie please? Gurumaister (talk) 07:30, 29 June 2011 (UTC)

Sorry, I don't know the answer, but this looks helpful. Tama1988 (talk) 08:12, 29 June 2011 (UTC)

A .cue extension is not an audio format in itself, but a text document that says how a CD's tracks are laid out. I don't have any experience using them. The way I would play FLACs would be to not use Windows media player, but rather a free player that will play those file formats without trouble. I like VLC media player, but see Comparison_of_video_player_software#Audio_format_ability for other options. Otherwise, the link Tama provided is your best bet for getting FLACs to play on Windows Media Player as is. Finally, you could convert the FLACs to a different audio format that is supported, like mp3: see this guide. There are lots of free audio format converters available. But if it was me, I'd rather just get a free media player that can play everything, rather than get a free audio converter, and then play the music on a non-free program. Buddy431 (talk) 05:39, 1 July 2011 (UTC)

Moderate (or just slight) network security for dummies

Or anyway a dummy: me. Sorry, there's something about networks: whenever I try to read how they work, I get totally confused and give up. Anyway, I have a dumb wired/wireless security question.

I work in a large organization. There are ethernet sockets all over the place. Anyone can bring any computer, plug it in, and get to the web. Here's the process: Point your browser to any URL, and up will pop the log-in screen. Feed that your ID and password, and you're in -- thereafter you can browse and download freely. (Surprisingly, you can do this for two computers at the same time. Though there seems to be some prohibition of bit torrents.)

I use this for such purposes as online purchases, when I divulge my credit card details. (Of course only with https and when I see the browser's little closed-padlock icon.) Is this stupid of me?

There are also wireless LAN access points all over the place. There's no encryption at all -- you too could stroll in (or sit in your car outside) and you'd get to the log-in screen. Even when I'm "https, closed-padlock", I avoid giving credit card details, etc, when connected wirelessly. Is it stupid of me to be worried?

The organization has just added a second wireless LAN (or second SSID). This one is password protected. However, it's a single password for everyone, and there's effectively no protection of the password. (If you wanted it, you could easily find it online.) I don't follow the logic here (but recognize that I'm an ignoramus). Does (A) an SSID that's encrypted but whose password is public knowledge have any advantage over (B) an open SSID? Tama1988 (talk) 08:04, 29 June 2011 (UTC)

Your primary question appears to be: Is https security safe? The quick answer is: Yes. The deal with networks is that it is layered. On the wires themselves, you have little 1's and 0's moving along (technically, they are electrons). From endpoint to endpoint, the hardware speaks a specific language. This is a packet-based language. One item of hardware will grab an imaginary packet (or envelope), put some information in it, slap an address on it, and send it to another one. The wires see 1's and 0's. The end hardware sees packets. Your software on your computer speaks in streams of data, not packets. So, you send an email. Your whole email streams out to the hardware. The hardware chops it up into chunks that will fit nicely into a packet. Each packet is sent off to the end recipient hardware. On that end, the hardware takes all the information out of the packets and streams it to some software on the other end. It should be obvious here that the little packets don't all take the same route from one place to another and don't necessarily travel in order. So, if I grab a packet off the internet, what do I have? I have a small chunk of some stream from some program. Useless. I have to get close to your computer's hardware to grab all the packets and then I can put them back together. So, there's another thing that you can do. You first contact the server you want to send something to. You put a secret key in a lockbox and put a padlock on it. That is sent to the other server. The other server puts its padlock on it and sends it back to you. You remove your padlock and send it back to the server. The server removes its padlock and reads the secret key. This could go the other way (the server sends the key to you), but what is important is that there is never a case where the secret key is travelling over the network without being locked (encrypted). Now, you and the server have a secret key that is very long and that you will use only one time. You encrypt your message with it. Stream the encrypted message to your hardware. The hardware packets it and sends it as 1's and 0's over the wires. Eventually, the server gets it and decrypts it. That is a very loose description of https. If someone were to be watching the 1's and 0's, they have many hurdles. First, they need to get all the packets. Then, they need to order them. Then, they need to decrypt the message - which is the hardest part. Because the message is short and the key is huge and never used again, decryption is nearly impossible. Notice that none of this has anything to do with being wired or wireless. -- kainaw™ 12:56, 29 June 2011 (UTC)

OK, I got it--as far as https goes, at least. (And yes, I do check all the signs that I really do have a proper https connections (not that I'd previously understood what that meant). Tama1988 (talk) 00:19, 30 June 2011 (UTC)

Windows Network Security. Pick two. Googlemeister (talk) 14:45, 29 June 2011 (UTC)

Network and security. I don't see how the OS is directly relevant to my question, but FWIW I don't use Windows. Tama1988 (talk) 00:19, 30 June 2011 (UTC)

As Kainaw said HTTPS pretty much guarantees no one in between will be able to decrypt your content without the cooperation of either end of the connection. So the issue is not so much do you trust the network but do you trust either end? The bank or whatever should not be a big concern. But what about the computer you are using? It's not clear to me if this is a personal computer or a work computer. If it's a work computer, do you trust whoever has adminstrative powers not to do something dodgy, e.g. install a keylogger or install a modified browser which makes you think you are visiting a secure site with a secure certificate verified by one of the normal root certificate agencies? Do you trust them to ensure no one other then them can modify the computers either locally or remotely (whether directly or with malware) to do one of those? If it's your own computer do you trust yourself to ensure your computer is secure and no one can do something like that? The 'remotely' part is perhaps important here, are your firewall and network security settings properly set up? Some OSes may give lower security on a LAN thinking the other computers are more trusted, but this is probably a bad idea in a work place (although not as bad as a public wifi access point or if you have dodgy flatmates since the network admins will often at least try to restrict what goes on in the LAN and there would be greater concern of the legal risks). Nil Einne (talk) 15:16, 29 June 2011 (UTC)

It's one or other of my computers. Nobody else has ever touched any of them. They're running Debian stable, fully updated and only from the right repositories. (There may be a common idea that Debian is for computer experts but it was pretty easy to set up and anyway I am no computer expert. And I know next to nothing about networks.) I haven't encountered any obvious restriction on what goes on via the LANs other than the prohibition of torrent downloads; the article on firewalls talks about "packet filtering" and maybe there's some of that; I wouldn't know.

Back to the first question. An institution has (A) a wired LAN that requires a personal ID and password. It also has (B) a wireless LAN with no additional requirements. It then adds (C) a second wireless LAN (or SSID) that requires a password for any use (before you get to the personal ID/password web page), but makes this additional password pretty public. "Common sense" tells me that (C) has no advantage over (B), but am I missing something here? Tama1988 (talk) 04:42, 30 June 2011 (UTC)

If the password is associated with WPA then the over-the-air content will be encrypted and even your non-https traffic with be difficult to impossible to read using wireless sniffers. --Phil Holmes (talk) 11:26, 30 June 2011 (UTC)

Ah, I think I've got it. By making the password to the SSID available, the organization of course lets anyone use it, but even if black hats are using it, then as long as it's WPA (and I'm ashamed to say that offhand I don't know if it is WPA), it's going to be difficult for these black hats to snoop at what I'm doing. I'm starting to get the picture ... I think. (I wonder if it's just me who's utterly baffled by network stuff, despite being unworried by most other day-to-day computer-related issues.) Tama1988 (talk) 09:43, 1 July 2011 (UTC)

How to creat a mobile phone app

So, I've got an idea for a mobile phone app. I've looked extensively through other similar apps, but have not found anything quite like what I envision. Without saying too much, the concept of the app is very similar to existing apps...just the "purpose" is different, and is what makes my idea unique. Anyway, a number of trusted friends I've talked to about this think its a really good idea, and something they would probably pay for. The problem is, I have no knowledge of even where to begin. Is there a good resource to teach myself how to create an app? Quinn ^{❀ BEAUTIFUL DAY} 16:18, 29 June 2011 (UTC)

It depends on the phone. iPhone apps are programmed in Objective C and you really need a Mac; then you get the iPhone SDK from Apple. Android apps are written in Java or C and you get the Android SDK from Google. J2ME apps are written in Java, and you get the SDK from Oracle. All three are fairly different environments and porting code from one to another isn't a trivial matter. -- Finlay McWalter ☻ Talk 16:28, 29 June 2011 (UTC)

I suppose since I have an Android, that I would go that route. What is an SDK? Quinn ^{❀ BEAUTIFUL DAY} 16:29, 29 June 2011 (UTC)

Software development kit. -- Finlay McWalter ☻ Talk 16:31, 29 June 2011 (UTC)

All of the phone platforms have developer guides like the Android Developer Guide. -- kainaw™ 16:30, 29 June 2011 (UTC)

Perfect! Thanks! Quinn ^{❀ BEAUTIFUL DAY} 16:53, 29 June 2011 (UTC)

Ad problems, the sequel

Referring back to this question, I have new information to add.

Some of the ads still appear, but not after I click any more. They gradually cover the screen after I have been at a particular location for a few seconds, and the "Close" link appears quickly (this didn't happen before) and works quickly enough (it was slow to do anything). Once, though, I thought I was clicking on "close" and ended up clicking on the ad itself, which was annoying. Anyway, these particular problems seem to be resolved.

There was one case where the "close" link was hard to find, and it said "roll over", whatever that means. So someone needs to explain themselves better.Vchimpanzee · talk · contributions · 18:21, 29 June 2011 (UTC)

The people who run the websites get paid if you click on an ad. It is in their best interest to do everything possible to make you click on the ad. So, why would they make the ad small, out of the way, and give it a big "Close Me" button? The solution is to stop visiting sites that use annoying ads. If nobody visits them, they will look for another way to make money. -- kainaw™ 18:36, 29 June 2011 (UTC)

I'm not going to stop visiting such sites. They need to be nice to their users. A big "Close me" button is the only way to do that when what you want has been covered up without your permission. They will hear from me otherwise and be told I will avoid doing business with any of their advertisers.Vchimpanzee · talk · contributions · 19:26, 29 June 2011 (UTC)

I'm certain they'll be impressed. --Tagishsimon (talk) 20:03, 29 June 2011 (UTC)

Of course, Jack in the Box and Citi have poisoned their reputations (in my view).Vchimpanzee · talk · contributions · 20:05, 29 June 2011 (UTC)

I just visited their sites and Idon't see any particularly obnoxious ads. Are you sure those ads are theirs? With respect to "I won't stop visiting their sites... I'll avoid buisness with their advertisers". What happens is you visit sites and click ads, on accident maybe, but that is you "doing business with them" and probably the only business they expect to get anyway. So they're already winning, so is the site you are visiting, who gets paid by the advertiser, and you lose by having yourself annoyed. The solution is either to use an ad blocker or stop interacting with sites who do this, ie don't go to that site. Of course, I'd verify it was the site popping these ads up, and not some sort of spyware/virus. Chris M. (talk) 20:38, 29 June 2011 (UTC)

I've already stated it's up to the library whether to use an ad blocker. And I did say the obnoxious ads no longer seem to be a problem.Vchimpanzee · talk · contributions · 21:14, 29 June 2011 (UTC)

Roll over usually means move your mouse cursor over the ad for it to popout or display something. In such a case avoid moving your mouse over the ad. Nil Einne (talk) 23:08, 29 June 2011 (UTC)

If these are library computers I suppose they are using Windows. (Why should a library use free software when it can instead use software that costs money?) If so, I'd click Alt-F4 at the sight of any obnoxious pop-up. There's no guarantee that either "Close" or a little "x" on a junk window will work to close it.

Further, if you anyway have a computer and sites look bad on computers over which you have no control, then prepare your own computer properly and thereby view garbage-free versions of the sites. Tama1988 (talk) 08:21, 30 June 2011 (UTC)

Alt-F4 will close the whole browser including any tabs (if the OP ever gets round to using them) which isn't what the OP wants. And it's also a little silly to get so paranoid about ads, I probably spend less time closing them then people do worrying so much about them and I've never found the need to use a popup blocker or ad remover other then what comes with my browser (even when visiting dodgy websites). Also with the vast majority of ads on non dodgy websites, clicking the x or close will remove it. Note we are not talking about popup windows here as explained in the op's earlier post but ads which display in the current browser window sometimes hiding the content completely until they are closed (or your browser doesn't visit the actual content until the ad is closed). The op apparently does not want their own computer and from memory of their user page needs to be careful with money so telling them to get one just to view news websites, even despite their persistent posts about issues with library computers is about as helpful as telling someone who is looking for reviews of US health insurance companies for individuals that they should move to Canada. Besides that from all the comments we have seen from the op it's questionable if a computer they have to administer themselves will be any better. Nil Einne (talk) 12:14, 30 June 2011 (UTC)

If you've seen my user page you know I have a computer. I don't use it to go to these problematic sites. It's not silly to get paranoid about ads because if they cause these problems it makes things very complicated. I don't need any further complication. And I'm not going to close the browser and I do not, will not, use tabs. I don't know how to get through to everyone. My mind does not and will not work that way. Windows are at the bottom of the screen. That's it.

And as I've said the problems seem to be resolved for now.Vchimpanzee · talk · contributions · 13:45, 30 June 2011 (UTC)

Just once in my life my computer (Win 2000 at that time) suddenly exhibited extraordinary symptoms of something. The browser (probably Mozilla Suite, though I forget all the details) showed screwy looking web pages saying rather alarming things. Then a very authentic-Microsoft-looking warning window popped up, suggesting that I install some antivirus software. The warning didn't have any spelling mistakes or obvious giveaways, but I couldn't imagine that I had deliberately installed any software that would detect a "virus" (malware), let alone any that would detect malware and do nothing with it other than prompt for the download of some other software. Somehow I guessed that the additional software would require credit card details, etc etc. I was less worried by any "virus" than by phishing and the rest. It seemed that some repellent bottom-feeding scam had managed to get one or two tentacles onto my computer, if you'll excuse the mixed metaphors. I don't remember if there was a "Close" button, but there certainly was a little "x". Given that the pop-up was designed to delude me into divulging my credit card info (or similar), I had no particular reason to think that clicking "x" would close the window--it might do something very different indeed. And so I hit Alt-F4.

Of course I don't recommend hitting Alt-F4 (or the non-Windows equivalents) at the sight of any ad. Perhaps I misunderstood the question, which I thought was about something serious. At the same time, I don't understand why anyone who has heard of AdBlock (Plus) wouldn't want to install it or something serious. Tama1988 (talk) 10:00, 1 July 2011 (UTC)

Now I see why there were those talking about Alt-F4. I should mention the library computer I had this problem with the most was Mozilla Firefox. I did, however, in one case get a virus or malware warning with one of these ads, and that was with Windows. Apparently some software the library had blocked the ad due to potential problems, but just that one time. I clicked on "Back" and that solved the problem (But if I do that I have to figure out how to get back where I wanted to be). But I don't click on the red X because I don't want to quit. As I said, the "Close" message has been easy to see in all cases recently. The "roll over" message was at the bottom and I wouldn't likely have seen it. I don't even know how I did.Vchimpanzee · talk · contributions · 15:55, 1 July 2011 (UTC)

HFS+ drive backed up onto FAT32 drive

A while back my family's iMac started experiencing troubles and we had to reinstall OS X. Before that I used Data Rescue II to back up the clone the contents of the disk (200+ GB) to a .dmg on a FAT32-formatted external hard drive. The .dmg is 4 GB—obviously nowhere near 200 GB—and cannot be mounted. I think that Data Rescue may have split it up into blocks and scattered them through out the drive, which is a Western Digital 1.5 TB My Book Home Edition. Viewing the information about this drive with Disk Utility reveals that it is 1.4 TB (which Disk Utility shows as 1,500,301,910,016 bytes—marketing, huh, 1.5 terabytes with 1 terabyte being equal to 1000^4 bytes instead of 1024^4 bytes) and that its capacity is 1.36 TB, a discrepancy. Could my "scattered" backup somehow be in this discrepancy? --Melab±1 ☎ 18:47, 29 June 2011 (UTC)

Marketing does not use powers of 2 when using MB, GB, TB, etc... They use "thousands" increments. If you want to be technical, it was the computer programmers and hardware engineers who incorrectly called 1024 bytes a kilobyte. So, all you have here is a disagreement between what you want kilo to be and what the mareting department is calling kilo. As for the actual size discrepancy, it is expected that the overhead required by the filesystem will take up room on the disk. The larger the disk, the more overhead you have because there is a lot of indexing and free-space management going on. Your data shouldn't be anywhere in the disk overhead area. As for having a file scattered around a drive - that is normal. There is no reason that a drive must keep a file in one continuous chunk. It is nice for humans to find a file in one piece, but a computer will happily hop around the drive grabbing up the little chunks to make one big chunk. -- kainaw™ 18:57, 29 June 2011 (UTC)

I know that marketing uses powers of 1000. Using the numbers that Finder displayed, I have around 74 GB on it. Remember that I backed this up into a DMG which reached the 4 GB limit of FAT32 files and I also did a deleted files recovery with Data Rescue 3 a few months later, probably contributing to the 74 GB. What I want to know now, is can I reconstitute the old backup? --Melab±1 ☎ 19:26, 29 June 2011 (UTC)

How can I reconstitute this back up? --Melab±1 ☎ 22:40, 29 June 2011 (UTC)

Make sure you show all files including hidden, system and protected files and look at the disk. Do you see any other files other then the single DMG? If not there's a very good chance the backup is not there, probably not carried out properly in the first place. Nil Einne (talk) 23:05, 29 June 2011 (UTC)

A few months after this I stored some recovered files on drive after I accidentally deleted a VirtualBox snapshot. --Melab±1 ☎ 23:36, 29 June 2011 (UTC)

What is the possible compression ratio of DMG files? --Melab±1 ☎ 00:43, 30 June 2011 (UTC)

That would depend entirely on the source content, Apple Disk Image says bzip2 (and others) is supported. Unless your content was nearly completely text files or something similar, a 50:1 compression ratio is very unlikely. It is also unlikely storing further files on the drive removed your backups although if the backup was done but somehow deleted it could have greatly reduced your chance of recovery. However I still go by my earlier comment, if there are no other files on the disk that you don't recognise there is likely no further backups and the most likely possibility is your backup wasn't carried out properly. I realise I forgot to mention this but you should always verify your backup before you need it, which means amongst other things, make sure any backup you carry out is done properly. Nil Einne (talk) 12:02, 30 June 2011 (UTC)

Shell script help

Resolved

Hi. I'm writing a little shell script and can't quite find the right way to do it. I have a gazillion files. In each file, each line is comma separated with words and numbers. But in a file, each line has a different number of entries, and the numbers and words are different lengths. I want to extract the number in the nth row, mth column of each file. I can get the nth row with "sed -n 2p" but I can't extract the mth entry on that line (which is a number). What is the best way to do this? Thanks, Robinh (talk) 21:32, 29 June 2011 (UTC)

You could use awk, as in this example: echo "hello,there,folks" | awk -v foo=2 -F"," '{print $foo}'

Where -v foo=2 sets the awk variable foo to 2; you'd set it to whatever m you wanted

and -F"," sets the field delimiter to a comma

-- Finlay McWalter ☻ Talk 21:47, 29 June 2011 (UTC)

A slightly more succinct version of which is awk -vm=1 -F, '{print $m}' -- Finlay McWalter ☻ Talk 21:48, 29 June 2011 (UTC)

Put more simply: awk -F, '{ print $m; }' ¦ Reisio (talk) 22:00, 29 June 2011 (UTC)

Thanks guys. Works perfectly. I've never really got to grips with awk. Cheers, Robinh (talk) 22:12, 29 June 2011 (UTC)

That's a workable solution, but if speed matters, it would be quicker to use cut rather than awk; that is, cut -d "," -f $m. Looie496 (talk) 23:58, 29 June 2011 (UTC)

Heh, even better! thanks again, Robinh (talk) 01:12, 30 June 2011 (UTC)

web designing tutions online for beginners [80 years old, Me]

I am Sunder Thadani, a netizen from Mumbai [age-80 years]. I wish to learn web designing. I need help/guidence on online tutions from the web [fee-free]. I have lates PC with Windows 7 and Office 2010 as platform. My knowldege on computer is good since I am using Net since 1999. Your attention will be highly appreciated. Sincerely, Sunder Thadani — Preceding unsigned comment added by Sunder360 (talk • contribs) 22:53, 29 June 2011 (UTC)

http://wsc.opera.com/ http://www.htmlhelp.com/ http://css-discuss.incutio.com/ http://www.brainjar.com/ http://www.htmldog.com/ http://css.maxdesign.com.au/ http://www.alvit.de/handbook/ ¦ Reisio (talk) 23:12, 29 June 2011 (UTC)

W3Schools is very helpful. --Melab±1 ☎ 23:37, 29 June 2011 (UTC)

Or was it harmful? http://w3fools.com/ ¦ Reisio (talk) 23:45, 29 June 2011 (UTC)

HTMLdog is also helpful. Unlike Resio, I also find w3Schools to be extremely helpful. TheGrimme (talk) 13:44, 30 June 2011 (UTC)

No doubt because you aren't informed enough to identify it as harmful. Check out the link. ¦ Reisio (talk) 18:29, 30 June 2011 (UTC)

Helpful or harmful depends on your opinion. But let's make clear: w3schools is a privately-operated website that is not affiliated in any way with the official World Wide Web Consortium (W3C) standards body. Nimur (talk) 17:47, 1 July 2011 (UTC)