Remove last char in vi

Following Linux commands can be used to replace last character in vi editor.

1. Open file using vi editor
2. Run the following command to replace last char

:%s/.$//g

3. Save file using :wq!

Create soft link in Linux

Suppose you want to create shortcuts in Linux, you can use 'ln -s' command to create soft links.

Ex :- If you need to run JAVA6 and JAVA8 both from terminal, you have to add java6 and java8 commands to /usr/bin for terminal execution.

Steps to keep java6 and java8.

1. Create two files in /usr/bin/ as java6 and java8
2. Extract JAVA6 and JAVA8 to Linux file system. Suppose directory locations are /usr/java6/ and /usr/java8/
3. Create Soft links for java6 and java8 using the following commands as root.

ln -s /usr/java8/jdk1.6.0_10/bin/java /usr/bin/java6

ln -s /usr/java8/jdk1.8.0_12/bin/java /usr/bin/java8

Now check versions using following commands in terminal.

java6 -version
java8 -version

Timestamp format in MySQL

This inbuilt MySQL command can be used to cast timestamp values as required.

SELECT DATE_FORMAT('field_name', '%Y-%m-%d %H:%i:%s') FROM 'table_name'

Above SQL will format timestamp in "YYYY-MM-DD HH:MM:SS" format. If you require only date you can format timestamp as following SQL.

SELECT DATE_FORMAT('field_name', '%Y-%m-%d') FROM 'table_name'

Add number of days to timestamp in MySQL

Following DATE_ADD('field_name', INTERVAL) can be used to increase the number of days in the 'field_name' in MySQL databases. 

SELECT SQL

SELECT DATE_ADD('field_name', INTERVAL 2 DAY)FROM 'table_name';

Update SQL

UPDATE 'table_name'
SET field_name= DATE_ADD('field_name' , INTERVAL 2 DAY)
WHERE 'id' = 1;