Why is umask setting a different permission for a directory and file I have created?

Question

Consider:

[user@server1 ~]$ umask
0770
[user@server1 ~]$ mkdir TEST2; touch TEST2.txt;
[user@server1 ~]$ ls -l
d------rwx 2 user group_name 4096 Mar  5 05:16 TEST2
-------rw- 1 user group_name    0 Mar  5 05:16 TEST2.txt

Now shouldn't the file TEST2.txt have the permission 007 as umask is set to 0770 ?

Thanks.

Answer 1

umask doesn't enforce rights, it forbids them. Have a look at strace:

file:
open("newfile", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = 3
directory:
mkdir("newdir", 0777)                   = 0

touch doesn't ask for execution rights for a file (which wouldn't make sense).

Answer 2

The umask value is permissions to deny, taken off whatever permissions would be given by default. A directory requires search permission, so unless overriden its permissions are 0777 (rwxrwxrwx), with the typical umask of 0002 it leaves 0775 (rwxrwxr-x). For an executable the same (x means execute here); for a regular file default permissions are no execute, rw-rw-rw- (0666), with the above umask 0664 (rwxrwxr--).

Answer 3

umask is a value that is basically the complement of the default permission value. So, if umask shows 002, that means the default permission is 775. Other examples for better understanding include umask=000 => perms=777 or umask=777 => perms=000 .