Yes it works! (I was as surprised as anyone)
It didn’t take me long to get it working but google returns a lot of posts with not so good information so here is the documentation on my experience.
I was recently tasked with writing a bash shell script that behaved differently depending on if it was invoked interactively (by a user at the command line), or non-interactively (cron).
There are surprisingly few useful results returned by Google. Both the “Advanced Bash-Scripting Guide” and GNU Bash manual mention testing to see if the prompt variable is set:
if [ -z $PS1 ]
but that will not work. For one thing, it’s perfectly reasonable for someone to have their prompt set to null, but aside from that, the prompt variables are not set when invoking a script so the test always returns the same result.
A coworker pointed out that that strangely, “man bash” has other ideas. In the Conditional Expressions section, it explains “-t fd True if file descriptor fd is open and refers to a terminal.” That sounds exactly like what we want:
if [[ -t 0 ]] ; then echo interactive else echo non-interactive fi
but there is still a problem. If you invoke the script remotely via an ssh call (e.g. ssh root@<remotehost> bashscript.sh”), stdin will not be connected to a terminal. To make the command more reliable we need one more test:
if [[ -t 0 || -S /dev/stdin ]] ; then echo interactive else echo non-interactive fi
Be aware that detecting a socket is also no proof of “interactivity”, but at least we are getting closer.
Yes it is possible to expand a software RAID1 device without loosing data. As a proof of concept we will create a small RAID1 device, then expand it. [read more]
Ever wonder where all your disk space has gone? On this new page I describe some useful tips to locate the offending files.
” Google Inc. is set to offer its free Android mobile-phone operating system for computers, opening a new front in its rivalry with Microsoft Corp. by challenging the dominance of the company’s Windows software. Acer Inc., the world’s second-largest laptop maker, will release a low-cost notebook powered by Android next quarter” [full story]
carrier to noise ratio
Android was a slow starter but is continuing to make waves… Inching closer and closer to that dream system.
In all of the SUSE varients (and in may other distros as well), the command ls has been aliased so that it actually does a ‘ls -la’. I find this particularly anoying so I have removed this configuration and documented it here: Stopping ‘ls’ from doing ‘ls -la’ instead.
Hot on the heels of my posting on the future of mobile devices comes a story on Venture Beat describing how they got the Google operating system Andriod running on an ASUS netbook.
Android’s Linux core seems to be giving it an early advantage due to Linux’s easy portability and vast hardware support. The article doesn’t mention it but some netbooks have support for 3G sim cards which just makes compelte sense.
I want to point out that a 3G enabled netbook running Android is still not the dream device I’m looking for but it’s getting close. The essential component of the dream device is the hardware. It must be cell phone sized but when docked, become a fully functional workstation (keyboard, mouse, full sized monitor etc.)
Netbooks aren’t the hardware solution. he netbooks are really just crappy laptops. Too big to carry around and with few of the “mobile” featuers that a smart phone would have.
They key aspect of the article is the discussion about how many manufacturers see Andriod as a replacement operating system to Microsoft based systems.
A group of researchers has posted a guide to turning a bunch of Sony PS3s into a supercomputing cluster. The researchers chose the PS3 it is a relatively inexpensive device with a powerful cell processor that “packs a punch.”
Other than the publicity it’s getting, there isn’t much thats new here. The PS3 has a been able to run “guest” operating systems such as Linux since it was released. Sony has even had some of its own employees working on improving it. And using Linux as an inexpensive clustering environment is certainly not new but it is still really cool to see something like this put together.
According to media reports (that get their news from Groklaw), the US District Court ruled that SCO does not own the copyright to Unix (Novell does). This effectively means the SCO has had their entire case pulled out from under them.
In a way this was a unexpected ending since originally the SCO case was all about the code. SCO had even gone so far as to show side-by-side comparisons of Linux and Unix code claiming this was proof that Linux had stolen code from Unix which they claimed to own. In the early days Linux advocates expected SCO’s attempt to show that code was stolen would fail miserably and that would be the end of it.
Unfortunately for SCO, screen shots of the supposed infringing code were leaked on the internet and quickly dubunked. Even more unfortunate for SCO, someone at Novell rememberd that the deal to sell Unix to SCO wasn’t quite what SCO thought it was and dug up the old deal which showed that it was actually Novell that still owned Unix.
SCO will likely appeal and there is still a chance the some of the rest of the case of SCO vs IBM will continue but does it really matter? While the legal issues are yet to be resolved, it was proven long ago that SCO will not have any significant or long term impact on Linux.
In the mean time SCO vs. Linux may have been a blessing in disguise. Things went so badly for SCO in so many different ways that it can only serve as a warning to other companies trying to put a stop to Linux through lawsuits. Microsoft has been rattling their patent saber for years but so far has not dared sue and one would think the SCO case had at least something to do with it.
I’ve finally figure out how to fix the display resolution on the PS3 running Linux. I’ve added it to my PS3 Linux page which is here.
