Linux: How to use an external hard disk, how to mount it

Problem: In my case I plugged the external hard disk into the USB port; a new folder with the name of my external HD was created, but it was empty.

Solution: I had to mount by hand the external hard disk, even if it was automaticaly recognized and a folder for it (empty) was created.

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The problem was that, when I plugged my external HD to the USB port of my Linux box, the disk was recognized and a folder was created under /media/NewHD , but the folder was empty. NewHD is the label, the name, that I choose when I first formatted my new USB external disk.

To solve I followed these steps:

1. You have to find the "dev" name of your external HD after you plugged it in:
   dmseg
   You will find something like these lines:
   
Initializing USB Mass Storage driver...
scsi6 : SCSI emulation for USB Mass Storage devices
Vendor: SAMSUNG Model: HM251JI Rev:
Type: Direct-Access ANSI SCSI revision: 02
SCSI device sdc: 488397168 512-byte hdwr sectors (250059 MB)
sdc: assuming drive cache: write through
SCSI device sdc: 488397168 512-byte hdwr sectors (250059 MB)
sdc: assuming drive cache: write through
sdc: sdc1

   From the last line you know that your external drive was mapped by Linux to the /dev/sdc1
   
   
2. You have to check if the external drive was actually mounted somewhere else:
   mount
   You get something like this:
   
[root@hece02] /media $ mount
/dev/mapper/VolGroup00-LogVol00_Root on / type ext3 (rw)
none on /proc type proc (rw)
none on /sys type sysfs (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
usbfs on /proc/bus/usb type usbfs (rw)
/dev/sda1 on /boot type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/mapper/VolGroup00-LogVol01_Home on /home type ext3 (rw)
/dev/mapper/VolGroup00-LogVol02_Scratch on /localscratch type ext3 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
AFS on /afs type afs (rw)

   If your /dev/sdc1 is present there, you know that you can access the content of your drive from the path associated with the /dev/sdc1. Otherwise keep following.
   
   
3. You have to mount the external hard disk:
   mount /dev/sdc1 /media/NewHD
   
   
4. And now you can access the content of your disk! :-)
   
   

When you have finished, you have to unmount it, before unplugging it from your Linux computer; something like the "Safely Removing" in Windows.
Just type:
umount /media/NewHD
then you can unplug it.

Python: Exception TypeError "argument of type 'instance' is not iterable" in 'garbage collection' ignored. Fatal Python error: unexpected exception

Problem: I got a nasty Fatal error message running my Python code: "Exception exceptions.TypeError: "argument of type 'instance' is not iterable" in 'garbage collection' ignored"

Solution: I forgot to use vars() function when checking the existance of a variable in an imported module

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I got this error in my Python code today, and it took me 20 minutes to understand where the bug was.

Actually the line number showed in the error message was false. The error itself started some lines above and it propagated until the incriminated line.

So this was the error:


Exception exceptions.TypeError: "argument of type 'instance' is not iterable" in 'garbage collection' ignored
Fatal Python error: unexpected exception during garbage collection
Aborted


And the problem was an "IF" statement where I checked for a variable name in an imported module:

My "IF" was this:


if 'fileName' in myModule:
fileName = 'OutputFile_%s.py' % myModule.fileName


To fix the problem I had to correctly add "vars()", of course ;-)


if 'fileName' in vars(myModule):
fileName = 'OutputFile_%s.py' % myModule.fileName


The bug was very stupid, just forgot the "vars()" function. But it was not so easy to find because the error message Python gave was not so helpful.

Eclipse IDE: How to install and configure MinGW GNU C++ compiler for Windows

Eclipse IDE has the very nice CDT environment for C++ programming.

In order to use it under Windows, you have to install a C++ compiler.

Our suggestion is to install the MinGW compiler, "A MINimalistic Gnu for Windows" Gcc compiler.

Go to http://www.mingw.org/ and download the installer for Windows from here.

Then start the Installer and choose to install the basic package + the g77 compiler + Make for MinGW, as those are the tools needed for compiling C++ code with Eclipse... and not only with Eclipse ;-)

Once installed everything you have to add the MinGW path to your PATH environment variable, to make the compiler findable.

Let's say we have installed the MinGW package on C:\MinGW. Refer to the picture below.
You have to open Start --> Control Panel --> System. In the pop up window that appears select on the left side "Advanced System Settings" and then goes to the tab Advanced and choose "Environment Variables...". There look for the "Path" variable in the System Variables window below (look for PATH, instead, if you want to set the MinGW compiler only for you as user) and click on "Edit...". In the pop up window you'll find a long string to edit. Go to the end of that string line and add ";C:\MinGW\bin". Then "Ok" and again "Ok".





Now your new nice MinGW compiler is ready to be used.

To make a test open a new command prompt (Start --> All Programs --> Accessories --> Command Prompt) and try to type "mingw32-make --version". If everything worked fine you should see a window telling you the version of the newly installed package.

Now open your Eclipse IDE with CDT for C++. Eclipse now should see and should be able to use MinGW C++ compiler!! :-)

So...have fun programming C++! :-)

Eclipse: How to get rid of the squiggly orange line in C++ editor

Problem: Using the Eclipse IDE with C or C++ code I have an annoying orange squiggly line throughout my code

Solution: Changing the C/C++ Indexer Markers options


Using the Eclipse IDE to programming C++ code, when an "include file" statement is not resolved, it is marked with an orange question mark and the whole code in the file we are editing are understriked with an orange squiggly line, as shown in the picture below.



It's really annoying, in particular when we are editing a file outside the real environment where the code will be compiled, and we already know that the included files are not physically joinable in that moment ;-)

So, in order to get rid of this squiggly orange line, just open the menu Window --> Preferences --> General --> Editors --> Text editors --> Annotations, look for the orange question mark symbol called "C/C++ Indexer Markers" and check out the "Text as" option, as shown in the figure below




In this way you can keep the orange question mark warning symbol in the Eclipse C++ editor, telling you that the "include file" statement is not working; but you can get rid of this annoying orange squiggly line, as shown in the figure below, and you get back a clean code! :-)