Linux Tips
Audio Volume in Shell Prompt
Code Folding in Vim
C Prog Debug Location
DMA for DVD and CD in RH8
J-Pilot symlink for USB cradle
Num Lock (.Xmodmap)
Remove Weird Filenames
Audio
Volume in Shell Prompt
You can put the current audio volume in your shell prompt with:
export PS1="`aumix -vq | cut -f3 -d' '` $ "
PS1 is the environment variable that bash uses for the command
prompt. The back quotes (``) mean run the enclosed command and
substitute the output every time the shell prompts you. The $ is a
traditional shell prompt character.
You can do this with other commands besides aumix if you want to
display other information in the prompt.
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Code Folding
in Vim
Vim versions 6.0 and later support a new feature called Code
Folding. With code folding, a block of code can be "folded" into
a single line, thus making the overall code easier to grasp.
The Vim commands to use code folding are quite simple:
To create a fold, position the cursor at the start of the code block
and type zfap.
To open a fold, type zo.
To close a fold, type zc.
To open all the folds, type zr.
To close all the folds, type zm.
For more commands and information on code folding in Vim, query Vim's
built-in help feature, :help folding. Also, make sure you are in
command mode when using this commands. If you are in text-entry mode,
typing "zfap" embeds the string in your text.
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C Prog
Debug Location
Tech Tip
Use the __LINE__, __FUNCTION__, and __FILE__ macros to identify where
you are in a C program. This could be handy for all those "debugging
printf()s".
printf("Welcome to line %d, "
"in the function %s, "
"in the file %s.\n",
__LINE__, __FUNCTION__, __FILE__);
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DMA for DVD
and CD in RH8
In their wisdom, the people at redhat decided to turn off DMA for CD
and DVD devices in an even "more reliable" way than before. To be
able to turn on DMA _at_all_ you have to add the following line in
/etc/modules.conf:
options ide-cd dma=1
Reboot.
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J-Pilot
symlink for USB cradle
/dev/pilot -> /dev/usb/ttyUSB1
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Num Lock
(.Xmodmap)
When you boot Linux, the kernel turns off Num Lock by default. This
isn't a problem if, for you, the numeric keypad is the no-man's-land
between the cursor keys and the mouse. But if you're an accountant, or
setting up a system for an accountant, you probably don't want to turn
it on every single time.
Here's the easy way, if you're using KDE. Go to K --> Preferences
--> Peripherals --> Keyboard and select the Advanced tab. Select
the radio button of your choice under NumLock on KDE startup and click
OK.
If you only run KDE and want Num Lock on when you start a KDE session,
you're done. Otherwise, read on.
To set Num Lock on in a virtual console, use:
setleds +num
If you choose to put this in a .bashrc file to set Num Lock when you
log in, make it:
setleds +num &> /dev/null
to suppress the error message you'll get if you try it in an xterm or
over an SSH connection.
Finally, here's the way to hit this problem with a big hammer--make the
numeric keypad always work as a numeric keypad in X, no matter what Num
Lock says. This will make them never work as cursor keys, but
you're fine with that because you have cursor keys, right? Create a
file called .Xmodmap in your home directory, and insert these lines:
keycode 79=7
keycode 80=8
keycode 81=9
keycode 83=4
keycode 84=5
keycode 85=6
keycode 86=plus
keycode 87=1
keycode 88=2
keycode 89=3
keycode 90=0
keycode 91=period
keycode 77=Escape
(from a Usenet post by Yvan Loranger:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=3BFD087F.2000300%40iquebec.com&rnum=3+)
The last line takes the now-useless Num Lock key and makes it an extra
Escape key. If your favorite accounting software uses one of the F keys
frequently, you might prefer that.
The number to the left of the equals sign is an X "keycode", the key on
the keyboard you pressed, and the number or name to the right is an X
"keysym", the character or function X thinks it is. You don't have to
look these up in some X manual. To find out the keycode and keysym for
any key, run xev in an xterm, move the mouse to the small white xev
window and watch the keycodes and keysyms scroll by in the xterm.
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Remove
Weird Filenames
If you want to remove a file called -rf, simply type rm -- -rf. The --
tells rm that everything after -- is a filename, not an option.
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