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Created by magnum on May 06, 2011 12:26:14    Last update: May 06, 2011 12:26:14
The bash environment variable PROMPT_COMMAND contains a regular bash command that is executed just before the command prompt is displayed. For example: $ export PROMPT_COMMAND=a bash: a: command not ... The command a is not valid so you get the error message every time you hit enter. Echo something before $PS1 : $ export PROMPT_COMMAND='echo -n Hi!' Hi!$ ... PROMPT_COMMAND is regularly used to change the xterm window title. You may find this in /etc/bashrc : case $TERM in xterm*) if [ -...
Created by Dr. Xi on March 28, 2011 11:11:33    Last update: March 28, 2011 11:13:21
grep is a versatile command with many variations (grep, egrep, fgrep, then various implementations). It uses a regula expression (regex) pattern to filter input. But then there are basic and extended flavors of regex - leading to even more confusion. And, beware that there are lots of bad examples of regex in the wild... There are two critical questions to ask when you use grep: which grep implementation are you using? what is the flavor of the regex? Here are some examples for gnu grep v2.7: # Find all numbers (no decimal point), basic regex... Use the -o flag to show only the matching part instead of the whole matching line: grep -o -E '\b[0-9]{2}\b' The good thing about the gnu grep is that it...
Created by voodoo on February 25, 2011 14:00:41    Last update: February 25, 2011 14:03:46
Suddenly my Windows XP failed to boot with this error message on a blank screen: missing or corrupt <windows root>\system32\hal.dll I took out the hard drive, put it in a USB enclosure and attached it to another PC. Then I ran CHKDSK and it fixed some file system errors. But I did find that hal.dll was intact, so hal.dll was not missing or corrupt . It turned out that the file that was really missing was C:\boot.ini . It is a hidden file, so you have to use attrib boot.ini to see it. The file is missing if attrib boot.ini returns nothing (run in the root folder C:\). In my case I reconstructed the boot.ini file: [boot loader] timeout=30 default=multi(0)dis... and changed the attributes back...