Monthly Archives: January 2010

MySQL Date and Time Functions

Posted by on January 28, 2010 No comments

Source: MySQL Date and Time Functions

Select count by day:

select count(*), DAY(date_time) 
from table n 
group by DAY(date_time) 
order by date_time desc;

speed up grep

Posted by on January 28, 2010 No comments

Re-posted from To be or not to be >> Speed up Grep:

GNU grep is very slow in the UTF-8 locale. It is orders of magnitude faster in the C locale. To check your current locale, type the following at shell prompt: locale

LANG=en_US.UTF-8
LC_CTYPE=”en_US.UTF-8″
LC_NUMERIC=”en_US.UTF-8″
LC_TIME=”en_US.UTF-8″
LC_COLLATE=”en_US.UTF-8″
LC_MONETARY=”en_US.UTF-8″
LC_MESSAGES=”en_US.UTF-8″
LC_PAPER=”en_US.UTF-8″
LC_NAME=”en_US.UTF-8″
LC_ADDRESS=”en_US.UTF-8″
LC_TELEPHONE=”en_US.UTF-8″
LC_MEASUREMENT=”en_US.UTF-8″
LC_IDENTIFICATION=”en_US.UTF-8″
LC_ALL=

In the above example, my locale is en_US.UTF-8. If you are
grep’ing very large files, you can greatly improve the speed by changing
the locale to C. In bash, you would type: export LC_ALL=C

Then type locale again, the display should look something like this :

LANG=en_US.UTF-8
LC_CTYPE=”C”
LC_NUMERIC=”C”
LC_TIME=”C”
LC_COLLATE=”C”
LC_MONETARY=”C”
LC_MESSAGES=”C”
LC_PAPER=”C”
LC_NAME=”C”
LC_ADDRESS=”C”
LC_TELEPHONE=”C”
LC_MEASUREMENT=”C”
LC_IDENTIFICATION=”C”
LC_ALL=C

Future version of grep are planned to address this issue. Until then, use the C locale with grep. If you are frequently using grep to search for large text files, you should include it in your .bash_profile.

egrep for linguists

Posted by on January 25, 2010 No comments

egrep for linguists

Egrep for linguists was written around 1997. It deals with different Unix/Linux commands useful for text processing. It contains examples of how to use regular expressions, egrep, sed, sort, uniq, cat, cut, tr, etcetera. The text has been used at university courses.

A PSA Reminding You Why We Need Documentation & User Guides

Posted by on January 14, 2010 No comments

Excerpted from How a Checklist Can Save Your Life:

“As experts, we will fail,” he said. “As elites, we will fail. The first thing they teach aviators, surprisingly, is, ‘You’re going to screw up. And it’s going to kill someone. Definitely you and maybe others….’

Due to increasing complexity in our jobs, it’s easy to lose sight of critical tasks. The argument for the checklist is that experts and leaders need written guides to walk them through the steps of any complicated procedure.”

“…In his book, Gawande distinguishes between ignorance, when the knowledge doesn’t exist; and ineptitude, when the knowledge exists but an individual or group of individuals fails to apply it correctly.”

Excerpted from How Checklists Can Keep You Alive After Surgery:

The problem with the checklist, as Pronovost himself learned, is that their use and control sets off a power struggle. He recommends nurses control the checklist, so doctors resist the process, because they don’t like taking orders from nurses.

The book: The Checklist Manifesto: How to Get Things Right