How to change a file permission?

You can change the file permissions using chmod command in unix. There are three sets of permissions user,group & world. You can assign numbers to each permission Using the numeric mode.For example:    4 = r    2 = w  1 = x

chmod 644 demo.php

Permissions Table

0              No permission

1              Execute permission

2              Write permission

3              Execute and write permission

4              Read permission

5              Read and execute permission

6              Read and write permission

7              All permissions