17.15 Searching for Files by Permission

[If you aren't comfortable with octal numbers and the way UNIX uses them in file permissions, article 1.23in is good background reading. -JP]

find can look for files with specific permissions. It uses an octal number for these permissions. The string rw-rw-r-- indicates that you and members of your group have read and write permission, while the world has read-only privilege. The same permissions are expressed as an octal number as 664. To find all *.o files with the above permissions, use:

% find . -name \*.o -perm 664 -print

To see if you have any directories with write permission for everyone, use:

% find . -type d -perm 777 -print

The examples above only match an exact combination of permissions. If you wanted to find all directories with group write permission, you want to match the pattern --w--. There are several combinations that can match. You could list each combination, but find allows you to specify a pattern that can be bit-wise ANDed with the permissions of the file. Simply put a minus sign (-) before the octal value. The group write permission bit is octal 20, so the following negative value:

% find . -perm -20 -print

will match the following common permissions:

If you wanted to look for files that you can execute (i.e., shell scripts or programs), you want to match the pattern -x--- by typing:

% find . -perm -100 -print

When the -perm argument has a minus sign, all of the permission bits are examined, including the set user ID bits (1.23).