Wikipedia:Reference desk/Archives/Computing/2010 October 13

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October 13

Where are they now and How can I get them ?

Two questions. I just had my college bag stolen out of my car - it was an old laptop bag, so they might have thought it had a computer in it - along with irreplaceable lecture notes, it contained what is known as a PE ACA scientific calculator, made in China. I purchased this and another in 2004 in a supermarket in Christchurch for about eight dollars each, and have not seen them sold anywhere since. The beauty of it, is one can programme a number of one's own formulae and equations in, in addition to ones already put in, and I would like to know where I could buy any more, since I enjoyed using it, and even assuming I get my bag and notes back, I am sure I can kiss that one and my Casio 9750 good bye. The other one I bought is broken - I made the mistake of putting it in my back pocket to carry around. Silly. Either that, or are there other calculators that allow one to programme equations like that ? I believe I still have my FX 82, which was not in my bag at the time, but is lost somewhere in my car and I could look for it - I see it has letters, but I know not if that allows one to programme equations.

My second question concerns a calculator, may be Casio, that came out in New Zealand in the early eighties. We called it the Space Invaders Calculator, as it had a game where you matched a number you could control with numbers as they built up across the screen, and if your controlled number matched one of the approaching ones, you could shoot it down before you got invaded. I had one, but one of my sisters took it to school in 1983, and it got stolen. I have not seen one since 1989 or early 1990 - does anyone know if they still make them, and where can they be gotten from ? Thank You. The Russian Christopher Lilly 03:52, 13 October 2010 (UTC)

When I was in high school, some 15+ years ago, we used to program formulas and games into our TI-81 calculators. I've never seen a PE ACA (article?) but it sounds a bit the same as a TI. Dismas|^(talk) 04:23, 13 October 2010 (UTC)

Thank You for that. If I cannot get another PE ACA, I shall try for a similar one of a different make.The Russian Christopher Lilly 06:47, 14 October 2010 (UTC)

External Hard Drives and USB ports

Hello, I own two USB external hard drives. I want to get another one, but my laptop only has two USB ports. Is there a device that is the same concept of a Power strip but for USB connections? If such a device exists, I do buy it, and I do connect my third USB hard drive to it, will I experience any problems (like all three hard drives competing for "resources"/"bandwidth" at once, slowing them down or any other problem)? -- 24.251.101.130 (talk) 12:18, 13 October 2010 (UTC)

Yes, you need a USB hub. As all the devices on a hub share the same connection to your PC, they share the bandwidth. But in practice, unless you're doing things like copying data wholesale from one disk on the hub to another disk on the hub, they're unlikely to all be moving data simultaneously, so the bandwidth issue won't be too bad. -- Finlay McWalter ☻ Talk 12:45, 13 October 2010 (UTC)

Thanks. If you don't mind, I have another question. I have a 2002-era internal hard drive. Is it possible to convert the internal hard drive to an external hard drive? Would it be a better idea to convert the internal and use it directly or make a copy of the disk image and move it to a new drive? What would be the preferred method of doing the latter; a product or a service? -- 24.251.101.130 (talk) 13:12, 13 October 2010 (UTC)

Yes, it's possible, but it's not worth doing. You can buy a USB disk enclosure (these are slightly different if the internal drive is a 2 1/2 inch laptop drive or a 3 1/2 inch regular size drive), transplant the internal disk into that, and then use it. But modern disks are so much bigger (more capacious) than a 2002 disk, it's not worth keeping that old one around. Ideally you'd clone the existing internal drive to one of your current external disks (with say Clonezilla), assuming there's space. Then you'd replace the internal drive with a larger modern one, and clone it back from the image on the USB. It looks like Clonezilla can resize the old, small partition to the size of the new disk. If your existing USB disks aren't big enough to accommodate the image of the internal disk, you can use a temporary adapter like http://www.amazon.com/dp/B0018MCGVU (it's just what I found with google, not a specific recommendation of a brand) and clone directly from the old disk to the new one. -- Finlay McWalter ☻ Talk 13:30, 13 October 2010 (UTC)

e/c Sure it's possible, but you've gotta work out if it's worth it (see here). A 2002 internal hard-drive in a laptop - so unless it was a very expensive laptop (and even then...) it would be pretty small, it would be relatively slow compared to current drives, and surely it must be nearing the end of its life (a general rule of thumb with any hard disk is not if it's going to break down, it's when). If you wanted to make it an external drive, I would personally recommend pulling the data off it, reformatting it, then putting the data back on, while putting a new disk in the machine with a clean installation of the OS. After eight years who knows what corruptions, etc, may have occurred, and data would quite possibly be badly fragmented and slower to access - copying the disk image would simply copy across all these problems. Reformatting and doing clean installations would help overcome these issues. IMO... --jjron (talk) 13:37, 13 October 2010 (UTC)

UND - Ubuntu's Not Debian: difference in "/etc/alternatives" system

I recently wanted to write a wrapper script around /usr/bin/mail and noticed that on Debian 5 (Lenny), it's a symlink to /etc/alternatives/mail, which is another symlink pointing to /usr/bin/bsd-mailx, while on Ubuntu 8.04 (Hardy Heron), /usr/bin/mail is the actual binary. Ubuntu does have an /etc/alternatives directory, but doesn't contain a link to the mail program.

I like the idea of using /etc/alternatives to link to my wrapper script. Is there anything I can do to use it on Ubuntu, without breaking package update mechanisms (i.e. when a new mail_somethingorother.deb gets rolled out, it will not get confused about the symlink in place of the expected executable)? -- 78.43.71.155 (talk) 13:38, 13 October 2010 (UTC)

Start your script with something like:

if [ -f /etc/alternatives/mail ]; then
    mail=/etc/alternatives/mail
else
    mail=/usr/bin/mail
fi

and then just use $mail to refer to the binary. --Sean 14:50, 13 October 2010 (UTC)

(edit conflict) Um, no, that's not going to help me achieve what I want to do.

The script snippet you posted is unneccessary, as /usr/bin/mail points to /etc/alternatives/mail, which in turn points back to the proper mail binary (/usr/bin/bsd-mailx).

What I want to - and can - do on Debian is changing the symlink from /etc/alternatives/mail to my own /usr/local/bin/mail-wrapper (which in turn calls /usr/bin/bsd-mailx), so that every program trying to use /usr/bin/mail will run my wrapper script instead.

old:
/usr/bin/mail -> /etc/alternatives/mail -> /usr/bin/bsd-mailx

new:
/usr/bin/mail -> /etc/alternatives/mail -> /usr/local/bin/mail-wrapper (which calls /usr/bin/mailx when done)

What I'm looking for is a way to activate the /etc/alternatives system (which is active for other binaries on Ubuntu, just not /usr/bin/mail) so that replacing /usr/bin/mail with my wrapper won't break the next package update for mail_whatever_foo.deb. -- 78.43.71.155 (talk) 15:54, 13 October 2010 (UTC)

You can configure any program to use the Alternatives system by following these instructions for update-alternatives (or using a graphical configuration tool like GAlternatives that wraps the command-line process). In Ubuntu, you would only have an /etc/alternatives/mail setup if (a) you installed multiple mail programs, and (b) the configuration-script in apt properly configured the alternatives for you. So if this is not already the case, you will need to configure it with the update-alternatives tool. Nimur (talk) 15:49, 13 October 2010 (UTC)

Interesting. So that means my Debian system contains another mail program, otherwise it wouldn't be using /etc/alternatives/mail. Now you got me curious. I'll have to check which one that is. :-) -- 78.43.71.155 (talk) 15:54, 13 October 2010 (UTC)

Okay, a quick check gives the following results:

• Debian uses /etc/alternatives/mail even though there is only one mail program installed
• Ubuntu has two packages containing /usr/bin/mail that cannot be installed simultaneously: Installing one will uninstall the other, and attempting to install both at the same time gives: mailutils: Conflicts: mailx followed by an abort.

Nimur, since you said any program can be set up to use the Alternatives system - is there a way to do so without breaking updates? If so, I couldn't find it in the link you provided. I know I could just do

echo '#!/bin/bash' >/usr/local/bin/mail-wrapper
echo '#do something here' >>/usr/local/bin/mail-wrapper
echo '/usr/local/bin/mail-real "$@"' >>/usr/local/bin/mail-wrapper
chmod 755 /usr/local/bin/mail-wrapper
mv /usr/bin/mail /usr/bin/mail-real
ln -s /usr/local/bin/mail-wrapper /etc/alternatives/mail
ln -s /etc/alternatives/mail /usr/bin/mail
#(or use update-alternatives for the two steps above)

...but I'm afraid that the next update will break this, either aborting as /usr/bin/mail doesn't look like expected, or overwriting either the /usr/bin/mail symlink or my /usr/local/bin/mail-wrapper script with the patched binary. -- 78.43.71.155 (talk) 16:15, 13 October 2010 (UTC)

Well, I think your work-around is functional, but it will probably get overwritten by the next update, unless you manually disable update for mail packages and hand-tune this each time you update mail tools. Alternatives is pretty robust; your actual program won't be uninstalled; but your "currently-selected" may get mucked around with. (I'm not sure exactly what conditions that will occur under, though). Maybe a shell alias (e.g. a setting in your .bashrc) is a more suitable workaround than moving/changing the contents of /usr/bin/ or /etc/alternatives/ ... ? A shell alias will never be modified by any update. The biggest issue I've found with using them is "inconsistent" behavior between scripts that execute with- or without- parsing your alias definition file (usually your .bashrc, but you could use some other login-script or dot-file). Nimur (talk) 17:37, 13 October 2010 (UTC)

Is there a place where I can put a system-wide alias?

The reason why I'm trying to wrap /usr/bin/mail in a shell script is that I want/need to log (to syslog, a text file, or a database - not sure yet what I'm going to use) all outgoing mail sent by the various daemons on my system, as some of it might be useful for debugging purposes, but I don't want every single bit of information ending up in my inbox.

That is why I want the wrapper to scan for "known harmless" subject lines (like "CRON-APT completed on..." telling me that it failed to download updates - at 2am) and have it skip over the line that calls /usr/bin/mail in that case. I know I could set an empty mail address in crontab, but I don't want the messages to get lost completely, I just don't want them in my inbox. -- 78.43.71.155 (talk) 18:00, 13 October 2010 (UTC)

Pricing question

A new computer with 4GB of ram is £300 from Pc World. I heard you can get 16gb of ram with fast cpu and etc for the same price if you build it yourself. is this truth? —Preceding unsigned comment added by 71.197.38.32 (talk) 13:51, 13 October 2010 (UTC)

Well, my goto for RAM Crucial.com offers a pair of 8GB sticks for £977.59 (inc. VAT). If you have a 4-slot motherboard, you could plug in 4 x 4GB sticks for £112.79 each. Those are DDR2 SDRAM. A pair of 8GB sticks of DDR3 would be between £751.99 and £902.39 depending on the data rate. Crucial prices are sometimes a bit more expensive than others, but I couldn't find anywhere which would sell 16GB of memory for £300 (never mind budgeting for a CPU, motherboard etc.) Also, if building/upgrading a computer yourself, you need to remember to budget other items such as cooling fans, power supplies and possibly additional cables and connectors. --Kateshortforbob _talk 14:25, 13 October 2010 (UTC)

There was a time when you could save quite a proportion of the cost of a computer by building it yourself, and it is still a good option if you need a non-standard configuration, but if the £300 model from PC World meets your requirements then there is little financial advantage to be gained in building it yourself because the builders of the PC World units can purchase parts in bulk at preferential rates. They also provide a guarantee that your computer will work first-time and that the components are compatible. Dbfirs 15:52, 13 October 2010 (UTC)

No, it's not truth, for the reasons Dbfirs writes above. I'll add that when you build the computer yourself you will probably choose improved-quality components — for example, HP sells many PCs with puny 300W power supplies — but the cost is not going to be lower than a commodity PC from HP or Dell. Comet Tuttle (talk) 18:29, 13 October 2010 (UTC)

Javascript

Resolved

In javascript for greasemonkey, how would you select the following checkbox:

<input type="radio" name="example" id="example2" value="1234"> <label for="example2">Checkbox</label>

82.44.55.25 (talk) 17:46, 13 October 2010 (UTC)

document.getElementById('example2').checked=true; -- kainaw™ 17:48, 13 October 2010 (UTC)

Thanks 82.44.55.25 (talk) 17:56, 13 October 2010 (UTC)

How do I get rid of this unwanted, unhelpful, search popup.

I use Internet Explorer 8 with Windows XP. This very unhelpful popup has recently started putting in an appearance whenever I use a search function on a website - any site. I really want to exterminate this irritating thing but I can't even identify it or find it anywhere on my PC. Screen capture image here [1] Roger (talk) 17:54, 13 October 2010 (UTC)

Sounds like malware. Install and run Spybot Search and Destroy and it ought to be able to take care of this. --Mr.98 (talk) 18:01, 13 October 2010 (UTC)

Resolved

Thanks! Spybot found a whole bunch of stuff including the offending popup thing. Roger (talk) 19:15, 13 October 2010 (UTC)

I urge you, today, go to Wikipedia:Reference desk/Computing/Viruses and do what it says in step 4 about user accounts. If you regularly use an account without administrator rights then it greatly reduces how badly you can be affected by malware. Comet Tuttle (talk) 19:35, 13 October 2010 (UTC)