Ernest Ho Diary

To remove the oldest file in Linux/Unix system:

rm `ls -1t  | tail -1`
rm -rf `ls -1td | tail -1`

If you would like to combine two fields of a table and add some characters between them, you can use concat.

For example, you have a table (usertable) which has email alias (field name: alias) and domain (field name: domain) and you would like to combine two fields as an email addresses:

select CONCAT(alias,'@', domain) as email from usertable;

+----------------------+
| email                |
+----------------------+
| susan@example.com    |
| peter@example.com    |
+----------------------+

So strange today, two people asked me why their Microsoft Outlook cannot print out a specified page of the email. For example, they cannot print out page 1 only.

Yes, it is true. If you just select the email title to view an email, you cannot print the specified page by clicking the printer icon or clicking "File" > "Print". In order to do that, you have to double-click the email title so that a new pop-up windows will be shown. You can now print out a specified page by clicking the printer icon or clicking "File" > "Print".