Converting Access Permissions

The statements below match access permission bits in alphabetic format to their corresponding octal numeric format:

1. r--r----- is 440
2. r-xr-xr-x is 555
3. rwxr-xr-x is 755
4. r-------- is 400

You can change file permissions using the chmod command. In Unix, file permissions, which establish who may have different types of access to a file, are specified by means of

1. access classes and
2. access types.

Access classes are groups of users, and each may be assigned specific access types.
The access classes are

1. user,
2. group,
3. other, and
4. all.

These refer, respectively, to the user who owns the file, a specific group of users, the other remaining users who are not in the group, and all three sets of users. Access types (read, write, and execute) determine what may be done with the file by each access class.