How do you change File Access Permissions?

Every file has following attributes:

Ø  owner's user ID ( 16 bit integer )

Ø  owner's group ID ( 16 bit integer )

Ø  File access mode word

'r w x -r w x- r w x' 

(user permission-group permission-others permission)

r-read, w-write, x-execute

To change the access mode, we use chmod(filename,mode).

Example 1:

To change mode of myfile to 'rw-rw-r--' (ie. read, write permission for user - read,write permission for group - only read permission for others)  we give the args as:

chmod(myfile,0664) .

Each operation is represented by discrete values 

'r' is 4

'w' is 2

'x' is 1

Therefore, for 'rw' the value is 6(4+2).

Example 2:

To change mode of myfile to 'rwxr--r--' we give the args as:

chmod(myfile,0744).