How to write text on end of txt file

Hi

I have a little problem .I need to add a text on end of existing text file.

For example:

I haveexa.txt file which have

105

110

115

in it.I want to add 120 on end of this text file like this

105

110

115

120

Can anyone help me o give me some example for this

Thanks

[360 byte] By [boske3a] at [2007-11-27 10:40:48]