linux

This weekend I encountered a weird problem during programming C extension modules for Python. For some obscure reason floats from my C extension modules were formatted with a comma as separater (e.g. 123,456) instead of with the more familiar point (e.g. 123.456). Obviously some locale related problem. Most of my desktop and applications are set up for Dutch (my native language), but when I'm programming/working I use English and scientific conventions (e.g. a point as decimal separator). After isolating the problem I found out it was related to importing the pylab (aka Matplotlib) module (which I started using for plotting graphs and figures from Python). The following situation illustrates the problem.

Man, this is heavy linux/unix commandline fun:

which which
locate locate
man man
help help
info info
whatis whatis
echo echo
touch touch
yes yes
whereis whereis

Today I bothered to intall the Last.fm player just to give it a try. The installation (on my Kubuntu 5.10 Linux laptop) was very easy. I just downloaded a tarball with the Linux binary from the Last.fm player download page and extracted it to a local folder in my home directory. Next I had to tell my webbrowser (firefox) to use this player for links with the lastfm:// protocol (like explained here). That was all to make it work.

Lets's start with a citation about the special parameters $* and $@ from the bash manual:

With the shortcut alt+F2 in KDE you invoke the "run command" dialog (also accessible from the start menu if it's not hidden of course). It is a fast and easy way to launch an application if you know its command line name (which is mostly the same as its normal name, except for things like OpenOffice.org).

If you're familiar with the Unix or Linux commandline you probably know cat for printing files to standard output. Rot13 is a simple text encryption/cyphering/obfuscation (or whatever you want to call it) technique. It replaces each letter with the letter 13 places further in the alphabet. For example: 'a' becomes 'n', 'z' becomes 'm' and 'n' becomes 'a' (which illustrates the fact that the rot13 operation and its inverse are the same).

Consider a program hello_and_error that writes to both stdout and to stderr. To redirect both to stdout:

hello_and_error 2>&1

If you want to redirect both to the same file hello.txt you can do in bash the following:

hello_and_error &> hello.txt

If you want to do this in a more obvious (but longer) way you should do

hello_and_error 1>hello.txt 2>&1

and not

hello_and_error 2>&1 1>hello.txt

If you work in a Linux desktop environment/windows manager like KDE, Gnome, IceWM (and probably many others), you definitly should try the following mouse trick: click/drag while holding <alt> above a (not maximized) application window. Depending on the mouse button and the windows manager this should move or resize the window. It's way easier than aiming at those thin window headers and borders.

For example in KDE and IceWM you can do the following:

• holding <alt> + left mouse button drag: move the window

When you want get rid of some files, but fully deleting them is bit drastic, a trash can is an handy option. In a graphical environment the tools are there to do it (drag and drop, right mouse button on a file, etc.), but on the command line it is not something very handy to do. In the old days there was a directory ~/Desktop/Trash that acted as the trash can. But nowadays, KDE and Gnome implement the freedesktop.org trash specification, which is more advanced than a simple directory with files.

Ever wondered what's the difference between ~/.bashrc, ~/.bash_profile, ~/.profile, /etc/profile, /etc/bash.bashrc (and maybe others) and what their purposes are? I do.

Some interesting excerpts from the bash manpage: