Archive for July, 2010

The Monkey business illusion

While watching this video, your job is to count how many times the players in white shirt pass the ball.

Tips on changing file permissions in bulk.

First command – changes all directories under the current directory to 700 file mode.

find . -type d -exec chmod 0700 {} \;

Second command – changes all files under the current directory to 600 mode.

find . -type f -exec chmod 0600 {} \;

time stamp on history

The ‘history’ commands does not display the exact date and time of the commands executed. It just shows a numeric id followed by  the command executed by the current user. Here is one way of putting a time stamp –

 export HISTTIMEFORMAT='%F %T  ' 

To make sure that it works every time you login or restart your machine, put it in $HOME/.bash_profile

Other useful environment variable related to the history command are –

The name of the file in which command history is saved.

The maximum number of lines contained in the history file.

A colon-separated list of patterns used to decide which command lines should be saved on the history list.

The number of commands to remember in the command history.

Setting clock

Some times you might be able to execute very complex commands and write pages of shell scripts and yet find your-self in a clueless situation, like the seemingly mundane task of setting the data/time in your Linux box from the command line. Here are a couple of ways that might help –

1. Using /etc/localtime and /usr/share/zoneinfo

Create a link to the file in /usr/share/zoneinfo which contains the time zone you want to set your clock to.

ln -s /usr/share/zoneinfo/America/New_York /etc/localtime

2. Edit /etc/sysconfig/clock

vi /etc/sysconfig/clock

-set the “ZONE” variable to your region – like “US/Central”

3.  Export command

Export TZ=America/New_York

4. Set the date using date command –


date -s '2010-07-09 13:19:55'

5. Hardware clock

hwclock --set --date='07/09/2010 13:19:55'