Wednesday, March 16, 2005

Linux resources

 
Find and bind key sequences in bash
 
Learn how to use keyboard function keys within bash, or any other shell, by binding the key sequences to a particular shell command.
Most keyboards today come with an extra row of function keys at the top of the keyboard. These function keys can be customized and used within bash, or any other shell, by binding the key sequences to a command in the shell. Some keys may be intercepted by the window manager or the terminal program, such as konsole or gnome-terminal. You can retain those key bindings and use unassigned keys inside the shell, or you can reconfigured them to use a certain key in the shell instead.
To obtain the key sequence from a function key, use the read command. The following is an example of pressing the [F12] key:
$ read
^[[24~
Note that different keyboards will produce different key sequences, and modifiers to the function keys (such as [Ctrl][F12] or [Shift][F12]) will produce other sequences as well.
The next step is to bind that key sequence to a particular shell command. For example, you can bind [F12] to the "history-search-backward" shell command:
$ bind '"\e[24~": history-search-backward'
Make sure you write the key sequence as \e[24~ rather than ^[[24~. This is because the ^[ sequence is equivalent to the [Esc] key, which is represented by \e in the shell. So, for instance, if the key sequence was ^[[OP the resulting bind code to use would be \e[OP.
Not only does the bind command bind function keys, but you can also use bind to map key sequences (such as [Esc][P] or [Esc][Q]) by writing the bind key code as \ep and \eq respectively.
For a list of shell commands that you can use, examine the /etc/inputrc file.
 
 
Apache
Analyze Apache logs with Analog
If you're looking for a useful log analysis program, check out Analog. This powerful, fast tool creates Web pages based on the analysis of Apache log files.
If your Linux vendor doesn't provide binary packages, you may have to download and install the program from source. After installation, create a configuration file that tells Analog what logs to read and where to place the output.
If installed via RPM or DEB, Analog will typically place a default configuration file in /etc/analog.cfg. Make a copy of this file, and customize it to fit your needs. Here are the essentials you need to set:
LOGFILE /var/log/httpd/access_log
HOSTNAME www.myhost.com
HOSTURL http://www.myhost.com
OUTFILE /var/www/html/logs/report.html
CHARTDIR /logs/images
LOCALCHARTDIR /var/www/html/logs/images
This tells Analog which log file to analyze, provides information on the host it's analyzing (i.e., hostname and URL), and indicates where to place the report file. (In this case, the resulting URL would be http://www.mysite.com/logs/report.html.) It also tells Analog where to write the image files for the charts that it creates.
Analog creates a very comprehensive output that includes a number of statistics, such as monthly page views, daily and hourly summaries of page requests, most used search requests to reach the site, and more.
For an up-to-date report, run Analog every day by using the following:
# analog -G +g/etc/myanalog.cfg
This assumes your customized configuration file is /etc/myanalog.cfg, and it tells Analog to use the specified configuration file instead of the default configuration file. This comes in handy if you've configured Apache to create log files for different virtual hosts and want a different report for each virtual host.

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