trk's weblog

GNU sed, replace search string with contents of a file

trkesavan — Mon, 09 Aug 2010 04:45:48 +0000

Say, I want to replace the text “replace me” in all the .txt files in the current directory with the contents of modified.js file

find . -name "*.txt" -print0 | xargs -0 sed -i -e ‘s/replace me/cat modified.js/e’

Notice the ‘/e’ at the end and that seems to do the trick.

jQuery empty(),remove() and Thickbox

trkesavan — Tue, 13 Jul 2010 10:09:29 +0000

I am a great fan of thickbox and I have used it for a long time. Recently I came across a situation where trying to close a modal that had a table with around 7000 rows (each 8 columns) crashed the tab in Chrome and took a very long time in Firefox.

I went through the thickbox forum and discovered that other people have had similar issues and they were related to the tb_remove() function. I did my own profiling and came to the same conclusion.Of particular interest was this statement:

$("#TB_window").fadeOut("fast",function({$(‘#TB_window,#TB_overlay,#TB_HideSelect’).
trigger("unload").unbind().remove();});

I looked at the documentation and then read through the comments where someone mentioned that remove() can be quite expensive due to stuff that it does and he suggested to use empty() before remove(). Voila, it worked! So for anyone else facing the same issue with thickbox, change the statement above to:

$("#TB_window").fadeOut("fast",function({$(‘#TB_window,#TB_overlay,#TB_HideSelect’).
trigger("unload").unbind().empty().remove();});

and see if that works for you.

Unix find, xargs and basename.

trkesavan — Sun, 11 Jul 2010 03:35:40 +0000

Xargs is great. If you want to know why use xargs over exec, have a read of this: xargs versus exec.

But, there is one problem. If the command that you are trying to execute on the results from find cannot take more than one file as param (basename for e.g, can take only one file), then use the -n 1 param with xargs (to process one file at a time) . In that case, xargs is probably going to be as quick as using exec.

find . -name "*.rar" | xargs -n 1 unrar e
find . -name "*.rar" | xargs -n 1 basename

And this will get the basename without using the basename function (I go it from this page).

find . -name "*.rar" -printf "%f\n"

Munin: Could not open required defaults file: /root/.my.cnf

trkesavan — Thu, 08 Jul 2010 01:08:56 +0000

For some reason I kept getting this error (even when the file was readable by all) in one of the munin (mysql slave) plugins that I had written.

So this was the solution that worked for me;

under the [mysql*] section in /etc/munin/plugin-conf.d/munin-node
I added this: env.mysqlopts -u{user} -p{password}

and in my plugin

I did something like this:

mysql ${mysqlopts} -e'show slave status \G'

and that seemed to have picked up the user and password from env.mysqlopts and the plugin started working (ofcourse after I restarted munin).

Fixing: “unknown terminal type” in shell

trkesavan — Thu, 08 Jul 2010 00:33:18 +0000

Assuming you are using bash
Add the following to ~/.bash_profile

TERM=vt100
export TERM

and then from shell

source ~/.bash_profile

Note: ‘vt100′ could be replaced with something similar in /usr/share/terminfo/

MySQL KEY, PRIMARY KEY and NOT NULL.

trkesavan — Mon, 28 Jun 2010 10:22:39 +0000

Have a look at this sql statement:

mysql> CREATE TABLE `t1` (`id` INT NULL AUTO_INCREMENT, KEY(`id`));
Query OK, 0 rows affected (0.92 sec)
mysql> SHOW CREATE TABLE `t1`;
+——-+————————————————————————————————————————-+
| Table | CREATE TABLE |
+——-+————————————————————————————————————————-+
| t1 | CREATE TABLE `t1` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
+——-+————————————————————————————————————————-+
1 row IN SET (0.08 sec)

See, how MySQL implicitly converts the NULLable column `id` to NOT NULLable because the column `id` was also a key?

Also have a look at the following statements:

mysql> CREATE TABLE `t2` (`id` INT NULL AUTO_INCREMENT KEY);
Query OK, 0 rows affected (0.11 sec)
mysql> SHOW CREATE TABLE `t2`;
+——-+————————————————————————————————————————-+
| Table | CREATE TABLE |
+——-+————————————————————————————————————————-+
| t2 | CREATE TABLE `t2` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
+——-+————————————————————————————————————————-+
1 row IN SET (0.00 sec)

Having KEY in the column specification makes that column a PRIMARY KEY!

I am going to go through these pages:
http://dev.mysql.com/doc/refman/5.0/en/silent-column-changes.html
http://dev.mysql.com/doc/refman/5.0/en/create-table.html

and try to understand why the context really matters while specifying the key. and also the reasoning behind implicitly changing stuff instead of throwing an error.ATM, it just doesn’t make any sense!

Q&A Site covering Religion and Philosophy

trkesavan — Sun, 23 May 2010 01:31:12 +0000

I have now been hosting a Q&A site covering 2 of my favorite topics: Religion and Philosophy. Link: bayankaram.com.

The name “bayankaram” refers to the legendary Sri Prativadi Bhayankaram Annan Swami who composed Suprabhatham.