Wikipedia:Reference desk/Archives/Computing/2010 March 24

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March 24

Is there a way to edit the html of a page while I'm viewing it?

Sometimes a page loads on my screen and I really need to make a small change (I don't like the width of the columns, or I want to highlight certain words, or something). The changes don't have to be permanent. Is there a way to make them while I'm viewing the page? If the page has webforms (e.g., a Wikipedia edit page), will those still work? 207.237.228.236 (talk) 00:14, 24 March 2010 (UTC)

Yes, Firebug (web development) does exactly this. You can edit the HTML of a specific tag (either of a leaf or a non-leaf) and the change shows in real time as you're typing. You can do the same for CSS (both in stylesheets and inline). The changes are indeed not permanent (they're overwritten on the next reload) but you can save the changed page. At the risk of sounding like a breathy fanboi, Firebug does all kinds of most excellent things for the web developer, and is in general pretty all-round fabtabulous. -- Finlay McWalter • Talk 00:45, 24 March 2010 (UTC)

Wow, this is a superb product. Thank you! 207.237.228.236 (talk) 01:19, 24 March 2010 (UTC)

Internet Explorer 8 does this as well. It's already built in, just hit F12 and the developer tools will load up. ZX81 ^talk 01:55, 24 March 2010 (UTC)

I type JavaScript into the address bar to edit web pages. You replace the web page address with code like this:

Make the page your viewing editable

javascript:document.body.contentEditable='true';document.designMode='on'; void 0

Go to Google images and run this to rotate images:

Rotate images on a page around

javascript:R=0; x1=.1; y1=.05; x2=.25; y2=.24; x3=1.6; y3=.24; x4=300; y4=200; x5=300; y5=200; DI=document.images; DIL=DI.length; function A(){for(i=0; i-DIL; i++){DIS=DI[ i ].style; DIS.position= 'absolute'; DIS.left=Math.sin (R*x1+i*x2+x3) *x4+x5; DIS.top=Math.cos (R*y1+i*y2+y3) *y4+y5}R++} setInterval ('A()',5); void(0);

And here's one I came up with myself. It blanks out all flash movies on a page:

javascript:for(i=0; i<document.getElementsByTagName("object").length; i++){document.getElementsByTagName("object")[i].LoadMovie(0, "f")}

--Chmod 777 (talk) 02:03, 24 March 2010 (UTC)

Yes, Firebug is great for JS debugging and small edits like deleting some obnoxious box in a page. If you want to permanently associate editing scripts with particular web pages, you want GreaseMonkey or for ad blocking, AdBlock Plus. If you just want to mess with Wikipedia pages for your own viewing, enroll an account and set up a customized WP:SKIN which is a javascript file called "monobook.js". 66.127.52.47 (talk) 04:17, 24 March 2010 (UTC)

Thanks, everyone, for the generous answers!!! I particularly am glad I learned about Firebug and also about all the cool things that I can do with javascript in my address bar. 207.237.228.236 (talk) 07:27, 26 March 2010 (UTC)

Looking for win 32 version of Apache httpd 2.0.64-dev

Help! I have Apache 2.0.59 running on windows server 2003. There is a vulnerability (mod_isapi module unload flaw CVE-2010-0425) which I need to patch for.

When I looked at the Apache website (http://httpd.apache.org/security/vulnerabilities_20.html) it states that the vulnerability was fixed in Apache httpd 2.0.64-dev

But no matter how hard I tried, I cannot find httpd 2.0.64-dev anywhere on the http://httpd.apache.org website.

Can someone please help. Thank you. 139.130.1.226 (talk) 00:30, 24 March 2010 (UTC)

I've not found definitive description of the Apache developers' naming conventions, but I think -dev is the name they give to "versions" in heavy development (which then turn into -alpha and -beta and finally the released version). So you wouldn't expect to see a -dev in a release mirror (because it's not a release); it's a less formal name they give to what they think 2.0.64 will be when they finally release it. This post suggests they haven't yet released 2.0.64 proper (which isn't surprising, as CVE-2010-0425 is only a few weeks old). For a definitive answer you should ask on the Apache-httpd developer's website, but I think right now if you wanted something approximating 2.0.64 you'd have to pull the tree and build it (doing so isn't hard), but then you're running unreleased and possibly untested code. -- Finlay McWalter • Talk 01:21, 24 March 2010 (UTC)

Or you can download the 2.0.63 source code, unzip, apply the patch for CVE-2010-0425 (you'll need patch for windows; how to apply a patch), then compile Apache. That is how you patch a server vulnerability. If you don't want to do that, wait for 2.0.64 to be released. Indeterminate (talk) 13:41, 25 March 2010 (UTC)

Surds on the TI-84 Plus

Is it possible to display surds on the TI-84 Plus? If not, is there a program I can get which will do it on the TI-84 plus? —Preceding unsigned comment added by 124.171.116.21 (talk) 01:51, 24 March 2010 (UTC)

TI-84 is a rather slow computer, but still a TI Basic trial-and-error program would find the most common expressions (m √a)/(n √b). Simply iterate through low values of m, n, a, and b. --Andreas Rejbrand (talk) 02:15, 24 March 2010 (UTC)

Does anyone have a link to a program to download that does that? —Preceding unsigned comment added by 124.171.116.21 (talk) 02:22, 24 March 2010 (UTC)

Ticalc.org is a good resource for this sort of program. Caltsar (talk) 15:30, 24 March 2010 (UTC)

Plugging an PC's network cable into a Cat-5 PBX wall jack fried the ethernet card

Today someone at work (it's unknown exactly who) plugged a PC network cable into a different "network jack." Apparently it wasn't a network jack, it was the Cat-5-sized connection to the PBX. (One port on every set of network outlets is apparently for that PBX and most of them are currently plugged into phones.) The tech guy told me that it fried the onboard network card. I asked him if it was a different voltage and he said yeah.

Is this a typical or common problem? Why use a PBX system that uses the same physical format as regular networked PCs, but make the electric format such that it would physically disable a network card? Is this some transition PBX system that was advanced enough to graduate from regular old phone cables to Cat-3 or Cat-5s, but not quite an IP-based system yet? NByz (talk) 02:52, 24 March 2010 (UTC)

It's the other way, RJ-45 has been a standard connector for multiline phones for ages, and UTP ethernet was originally designed around the existing availability of cheap phone cables and connectors. I got no clue about PBX's but if I had to guess, I'd imagine they use a 45 volt ring current just like a POTS phone, and that's what fried your network card. 66.127.52.47 (talk) 04:14, 24 March 2010 (UTC)

The connector itself is called 8P8C officially, although RJ-45 is widely (incorrectly) used to describe 8P8C connectors in general. The 8P8C connector in the PBX could be for a DS-1 (T1/E1) line. I've heard the story before of an Ethernet card being fried by the higher voltage of a T1. 98.226.122.10 (talk) 06:14, 24 March 2010 (UTC) Wait a minute... on reading that again, if there was a (plain, single-line) phone plugged into the jack then it wouldn't be a T1, it would be a true RJ-45 and I'll agree with 66.* above that the RING is what zapped it. 98.226.122.10 (talk) 06:17, 24 March 2010 (UTC)

An 8P8C has eight connections. This is more than enough for most uses, and gives a flexibility that makes it the overwhelming choice for office structured cabling deployments. This means computer networking (4 connections), analog telephony (2 connections), digital telephony (4-6 connections), alarm circuits (2 connections, I think), cc-cameras (3+), LonWorks (2, possibly + power) and other stuff can all be run from the same rack through the same infrastructure. The downside is that there are too many possible uses of the pins to set things up so that accidentally connecting one type of device to another won't have deleterious consequences. And the (apparent) ease of reconfiguring the cabling can fool people who think they know what they're doing into making such a bad connection. In your case it's likely that your office has a digital PBX system (which are either IP or a proprietary protocol) and a regular ethernet; the telephones connected to the PBX need power as well as signal (and at a nontrivial voltage, as they're now fairly sophisticated computer devices with screens and stuff). Good colour coding can help avoid accidental problems, but nothing can save you if someone appoints themselves tech-savant and starts repatching with abandon. -- Finlay McWalter • Talk 09:58, 24 March 2010 (UTC)

The internal PABX shouldn't use the ring line, it is not needed with modern phones and the signal on it can cause noise on lines near it. Then again you may have a BOFH with an etherkiller on your site :) Dmcq (talk) 10:30, 24 March 2010 (UTC)

That's certainly true, but it's still common for there to be analog lines present in the building - either real inbound analog lines (for ADSL, fax, and power-fail-backup) and ones synthesised by the DPABX (for fancy conference phones and again for fax). -- Finlay McWalter • Talk 10:40, 24 March 2010 (UTC)

There is a significant advantage in having phones running through RJ45 ports under each desk. If the desks are rarely moved, but the data and voice requirements at each desk change with whoever is assigned to a desk, it makes sense to have a common infrastructure to each desk (especially if you consider the disruption, time and cost of ripping up the floor every time someone needs a second phone line or extra data connections).

For example: My desk has two PCs and a phone but under the desk there are four identical RJ45 ports. The phone is plugged in to the only port labelled with a "T". However, the real distinction between which ports are phone and which are data is made in the "network cupboard" where the entire floor's network infrastructure comes together in a large patch panel and the phone connctions are patched to the PBX cabling. Astronaut (talk) 13:00, 24 March 2010 (UTC)

What is the future for SUN Microsystems

Now that ORacle has eaten the SUN. What is the future for SUN Microsystems and it's legacy? 122.107.207.98 (talk) 07:15, 24 March 2010 (UTC)

We don't speculate about the future on the reference desk. Here's the official plan from Oracle: poster for Sun customers. Nimur (talk) 09:02, 24 March 2010 (UTC)

Yeah. And we all know how good Larry Ellison's word is.^{[1], [2], [3]}--Chmod 777 (talk) 10:06, 24 March 2010 (UTC)

There have already been some very profound changes in various Solaris licensing schemes, and evidence that both MySQL and OpenSolaris will be better supported by forks. That's not speculation, sadly. 99.56.136.197 (talk) 15:20, 24 March 2010 (UTC)

fastest browser

Which net browser is the fastest lately???? —Preceding unsigned comment added by 119.235.54.67 (talk) 09:08, 24 March 2010 (UTC)

Google says Chrome (browser) is. Aaadddaaammm (talk) 09:22, 24 March 2010 (UTC)

IE is the fastest to crash. Lynx (web browser) and Links (web browser) are pretty fast. --Stephan Schulz (talk) 10:21, 24 March 2010 (UTC)

Lifehacker publishes regular browser speed tests e.g. [4] comparing Firefox 3.6, Chrome 4 and Opera 10.5, and I would personally trust lifehacker to be fairly impartial. Note that different browsers tend to be fastest at different things (startup time, javascript etc.). That said the fastest browser is indeed probably a text based browser such as Lynx (web browser), but that comes at the expense of a lot of functionality. Equisetum (talk) 11:04, 24 March 2010 (UTC)

I'll speak to the functionality of modern versions of Lynx. I often find myself connecting to the internet in very weird ways; when I need email or internet over a 100 bit-per-second connection, I can trust Lynx to not only function, but to do so with great tolerance for crummy connectivity. I can view and edit Wikipedia; I can transcode and downlink an MP3 news update from Voice of America, I can browse with full colorized hypertext to mimic the formatting of a general "web 2.0" website, I can block advertisements, and much more. On these kinds of flaky or slow connections, Firefox, Opera, and other "standards" all suffer timeouts, graphics kludges, and total system failure. So, by that standard, Lynx is by far the fastest browser in terms of scaling down the latency chain - when the network can deliver 100 bits, Lynx uses 100 bits for useful work (while Firefox blows it on a frivolous AJAX request so I can see an animated twitter logo). I currently have Lynx Version 2.8.7pre.6 on Ubuntu 9.10, and it is fantastic as a failsafe browser. Nimur (talk) 15:52, 24 March 2010 (UTC)

is there any software that can answer trivial questions about "is there any number that?"

Is there any software that can answer trivial question ssuch as "is there any integer that is both less than 0 and greater than 0" or "is there any integer that is equal to 8 and that is equal to 9?" Thank you. 84.153.234.218 (talk) 14:29, 24 March 2010 (UTC)

In plain language? Probably not. When expressed in algebraic language? Any scripting language can do this quickly. The question is whether you are trying to get the software to parse English for you or whether you are trying to get it to parse logic/math. For a computer the latter is a trivial task when put in the right terms. --Mr.98 (talk) 15:11, 24 March 2010 (UTC)

For a lot of things, it's possible to put together a quick program to find something like that out. But not always, even if the terms are well-defined. For example, the question "is there any even integer greater than 2 that isn't the sum of two primes?" has eluded mathematicians for over 250 years.

You can sometimes coerce Wolfram Alpha into solving these kinds of problems (http://www.wolframalpha.com/input/?i=x+>+0+and+x+<+50+and+prime(y)+%3D+x), but figuring out its language is hard. Paul Stansifer 15:28, 24 March 2010 (UTC) dangit, corner cases of MediaWiki syntax are hard, too

This shell script will correctly answer your example questions and others like it:

while read; do
  echo "No."
done

--Sean 15:40, 24 March 2010 (UTC)

Any of the programs listed at Interactive theorem proving should be able to do this. (Though I'm not an expert at using them.) Fair warning: these things are very difficult to use. Staecker (talk) 16:41, 24 March 2010 (UTC)

Depending on how complex you get, and how you word it, Wolfram Alpha Alpha might be able to do it. Like, "is 65537 prime", which is pretty cool. Shadowjams (talk) 05:29, 25 March 2010 (UTC)

Ticker tape transmitter keyboards?

Ticker tape, originally from 1867 stock ticker printers, was in use until the early 1970s, and seems to me an indelible part of the western psyche because of the fact that the ticker tape parade was for several decades the highest de facto honor bestowed on war, science, and exploration heroes by the populace. It is easy to find pictures of and descriptions of the ticker tape printers, but I have only been able to find this lithograph ("Sending Messages over Ticker System," Scribner's Magazine, July 1889) of the transmitter, described thusly: "As of 1883, quotations were sent using a transmitter, 'the keyboard of which has much the same appearance as the keyboard of a piano, the black keys representing letters and the white keys figures and fractions.' When an operator struck a key on the transmitter, one of two small wheels (one for letters, the other for numbers) in each connected ticker revolved until the desired letter or figure came into position to print on a paper tape that passed through the device."[5]

This is the earliest example of digital telecommunication equipment, so it would be great if we could get a better picture of one of those keyboards. There are thousands of ticker tape machine pictures easily available, but are there any surviving transmitter machines or a better picture of their keyboards? 99.56.136.197 (talk) 15:04, 24 March 2010 (UTC)

Getty images http://cache4.asset-cache.net/xc/JH5652-001.jpg?v=1&c=IWSAsset&k=2&d=2AC75F6FAA20674CD1900A18F97E500B0EF1EBF13E19BD2549207362A3F24453 may be too modern for you. -- SGBailey (talk) 17:00, 24 March 2010 (UTC)

I don't know how that photo is labeled at Getty, but it shows punched paper tape which isn't really the same thing as ticker tape. --LarryMac | Talk 18:21, 24 March 2010 (UTC)

Also this one? http://www.juliaauctions.com/auctions/archived/toy/jun01/pict0113.jpg -- SGBailey (talk) 17:02, 24 March 2010 (UTC)

That seems to be an ordinary mechanical typewriter mounted below a ticker tape printer. 99.27.201.226 (talk) 19:36, 24 March 2010 (UTC)

Caret browsing

My Mac offers me caret browsing, but nowhere in the Help or manual is caret browsing explained... please somebody put me out of my misery.Froggie34 (talk) 16:17, 24 March 2010 (UTC)

caret navigation — look for your cursor, press some arrow keys. ¦ Reisio (talk) 16:54, 24 March 2010 (UTC)

You're talking about your web browser, right? Here's how normal mode and caret browsing mode differ:

In the normal mode, the arrow keys will control the scroll bars and scroll the window immediately. If you want to select some text on the page, you have to use the mouse.

In caret browsing mode, a text cursor (a blinking vertical line) is always visible on the page, even on parts of the page where you can't edit text. The arrow keys move the text cursor, and only once it goes beyond the edge of the window does the window scroll. You can select text without using the mouse: Move the text cursor to where you want to start, then hold Shift while you press the arrows keys to highlight what you want. --Bavi H (talk) 02:50, 25 March 2010 (UTC)

There is a difference between a (mouse) cursor and a (edit control) caret. --Andreas Rejbrand (talk) 16:41, 28 March 2010 (UTC)

Cloning a linux install, then using the hdd image on a different pc

Hi Wikipedians,

I am not sure how to do it (or if it is possible at all): I wan't to be able to clone a linux install (Centos, running Asterisk) as a means of backup, Is there a way to use a cloned image with another machine? ex: Clone the HDD on System A, then if say System A's board dies out, use the cloned HDD on System B (both systems have dual NICs btw)? I am primarily concerned regarding the network interfaces / devices working properly, as I've noticed sometimes with the same machine, one install may label a different NIC for ETH0 or something. Also, will it matter if System A happens to be Multi-Core and System B single-core?

Software recommendations would be welcome.

Thanks for helping a Linux Newb :) PrinzPH (talk) 18:37, 24 March 2010 (UTC)

I've done just this (strictly moving a linux install from one machine to a quite dissimilar newer one, but that's the same effect as what you propose). I just plonked it in the new one and it worked. The only thing that didn't work (out of the box, without me doing anything) was indeed the assignment of the ethernet adapter. On the system I was using (a recent Ubuntu Linux) these were assigned by udev according to /etc/udev/rules.d/70-persistent-net.rules which contained a line that said (in essence) "reserve /dev/eth0 for a device with MAC foo". In the new machine the ethernet adapters were different, so that rule didn't find anything to match, but udev reserved /etc/eth0 anyway (it does that incase you want to have a removable adapter, like a USB one, always be at the same device name). The kernel found the installed ethernet adapter in the new machine and assigned it to /etc/eth1. As the /sbin/ifup script (and its buddies) were coded for eth0, they didn't bring up eth1, so the machine had no internet. The fix is simply to comment out the rule lines in /etc/udev/rules.d/70-persistent-net.rules, which leaves the kernel to assign whatever ethernet adapters it finds to whichever /dev/eth? devices it thinks best (in essence by PCI discovery order). The only other thing I can think of is if you have a device driver that isn't managed by your dist but by yourself - I know next to nothing about Asterisk installs, so I don't know how it gets drivers for things like linecards. I also know nothing whatever about Centos, so I don't know if it has udev or devfs (which does the same job, but differently). -- Finlay McWalter • Talk 19:05, 24 March 2010 (UTC)

As long as the systems are the same arch, the worst case scenario is that you'd have to make a tweak or two as Finlay's described, and maybe add some new drivers to your kernel, etc..* ¦ Reisio (talk) 00:06, 25 March 2010 (UTC)

With binary distributions such as CentOS, it's often possible to plug the drive into another computer, even with a closely related but not identical architecture. A 32-bit installation originating from a 32-bit x86 computer can be plugged into an x86-64 computer, for example. In that case, the processor will run in backwards-compatibility mode, which means you cannot address more than 4GB RAM, but it will work nonetheless. (However, plugging an x86-64 installation into an x86-32 computer will not work.) There is one very important caveat when moving installations between processors, though: any programs compiled with GCC's -march= flags may need to be recompiled even between identical architectures but different processor models. -march applies aggressive optimisations for specific CPUs, even at the cost of compatibility with other CPUs, meaning the machine code may not be compatible even between two closely related CPUs by the same vendor but with a different model number. On CentOS, the only programs potentially affected by that are the ones you have compiled from source. --Link ^(t•c•m) 08:19, 25 March 2010 (UTC)

Firefox - Add-ons no longer shown in menus

I have Firefox 3.6.2. The Add-ons no longer appear in the menus anywhere. When I click on any "options" button in the Add-on page, that page freezes. As far as I recall it was working OK after recently downloading the 3.6.2 version. This might perhaps be connected with running the program called CleanUp! shortly before, although when I ran it on previous occassions with the same settings it didnt cause any problems. Anyone know what the solution might be? Thanks. I have tried re-starting the computer. 78.149.167.173 (talk) 21:21, 24 March 2010 (UTC)

I'm running the same version, I have no problem navigating through any menus. I can't find any "options" button in the Add-ons window, did you mean the "options" in the "Tools" menu? What OS are you running? 24.189.90.68 (talk) 22:28, 24 March 2010 (UTC)

All the Add-ons have disapeared completely, they are no longer in any menu nor at the top of the browser. However they are listed in the Tools/Add-ons page, but when I click on any Options button on that page freezes and I have to press Ctrl-Alt-Del to close the page. I have WinXp, Sp3. 84.13.22.69 (talk) 13:03, 25 March 2010 (UTC)

Hmm, maybe Firefox didn't update your add-ons properly, and now they're crashing FF? You might try Manually uninstall extensions and/or Manually uninstall plugins, and then reinstall them if that fixes the Add-ons tab. Indeterminate (talk) 13:22, 25 March 2010 (UTC)

Would it be easier to simply uninstall Firefox, re-install it, then reinstall all the plug ins? Perhaps I ran the CleanUp! too early after upgrading to 3.6.2 and it deleted something important. I may not have restarted the computer between using them. 84.13.22.69 (talk) 15:01, 25 March 2010 (UTC)

I did uninstall everything and then reinstall everything, and now it is working OK. I havnt tried running CleanUp! again yet. 84.13.34.56 (talk) 13:21, 26 March 2010 (UTC)