06-29-2009
umask explanation
I thought to post the information related to umask which i have read it from sites so that it might be helpful to someone who comes across this thread ...
$ umask
022 (this is the default value in my system)
For files, the permission settings are 0666 and for directories it is 0777
Having known the umask value, try creating a directory and a file and check what the file settings are
$ mkdir tempdir1
$ ls -l
drwxr-xr-x 2 root root 4096 2009-06-29 10:42 tempdir1
$ touch tempfile1
$ ls -l
drwxr-xr-x 2 root root 4096 2009-06-29 10:42 tempdir1
-rw-r--r-- 1 root root 0 2009-06-29 10:43 tempfile1
Change the umask and again create a directory and a file and check the file permission settings
$ umask 027
$ umask
0027
$ mkdir tempdir2
$ ls -l
total 12
drwxr-x--- 2 root root 4096 2009-06-29 10:40 tempdir2
$ touch tempfile2
$ ls -l
drwxr-x--- 2 root root 4096 2009-06-29 10:40 tempdir2
-rw-r----- 1 root root 0 2009-06-29 10:40 tempfile2
Now, let us see how the file permission settings are calculated using boolean expression.
For the directories, you need to take the 1's complement of the umask value and perform a logical AND operation with 0777.
For e.g. consider the case where we have umask value of 027 - 0000 0000 0010 0111
1's complement of 027 - 1111 1101 1000
For directories perform logical AND operation with 0777 (0000 0111 0111 0111). So
1111 1101 1000 (1's complement of 027)
0111 0111 0111 (0777)
-------------------
0111 0101 0000 = 0750
For files, perfom logical AND operation with 0666 (0000 0110 0110 0110), so
1111 1101 1000 (1's complement of 027)
0110 0110 0110 (0666)
-------------------
0110 0100 0000 = 0640
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
in this unix book that i have, it says:
the statement:
filedes = open(pathname, O_CREAT, mode);
is actually
filedes = open(pathname, O_CREAT, (~mask)&mode); /* ~ is the negation symbol */
like it's doing some type of masking.
for example,
fd =... (1 Reply)
Discussion started by: bb00y
1 Replies
2. UNIX for Dummies Questions & Answers
the umask on solaris must return 022 or 0022
wich one is correct and why?
thanks,
pa (2 Replies)
Discussion started by: rsh
2 Replies
3. AIX
I changed the umask in /etc/security/user to 027.
I changed the umask in /etc/profile to 027.
My current shell is ksh.
My .profile doesn't make any changes to umask or call other scripts that change umask.
Running AIX 5.3
I still get a umask of 022 instead of the expected 027. I have no... (1 Reply)
Discussion started by: x96riley3
1 Replies
4. Linux
hai guys ,
i am having problem in getting the knowledge about umask.
actually when i am putting command as umask some value is coming like 0022 by defalut.
we can change its value also.
but the main thing is thye file permisiion actually depends upon umask.how is it depends upon umask i want to... (6 Replies)
Discussion started by: suvendu4urs
6 Replies
5. UNIX for Dummies Questions & Answers
Hi,
I have a doubt on the umask values.
Why is the UMASK value is different from file and directory?
Suppose if the umask value is 0022. The file permissions for a newly created file is 644 and the file permissions for a newly created directory is 755.
My doubt is why can't it be the... (1 Reply)
Discussion started by: praveen_b744
1 Replies
6. Solaris
Due to urgent requirement to resolve some permission issues , I wish
to set solaris 8 server so that any file written is on 777 .
I guess need to set umask , how to set it ?? (7 Replies)
Discussion started by: falcon16
7 Replies
7. UNIX for Dummies Questions & Answers
I need to set a umask of 022 for my ssh sessions, or within my profile.
I have set the umask in both bash_profile and bashrc.
and when i run umask i get 0022 but when i create a file i get,
# touch test.txt
# ls -l test.txt
-rw------- 1 root root 0 Apr 26 12:25 test.txt
it seems like... (1 Reply)
Discussion started by: felix001
1 Replies
8. AIX
How do I change the umask for a NIS user?
Thanks
steve (1 Reply)
Discussion started by: steve.lavoie
1 Replies
9. Shell Programming and Scripting
Hi,
I want to set umask value only for vi editor.
If I create new file using vi editor, then automatic permission should be 777.
I want to set umask 000.
Please help me.
Thanks in advance (2 Replies)
Discussion started by: mnmonu
2 Replies
10. UNIX for Dummies Questions & Answers
Hi guys,
I want all new files and directories created, or copy file give this permisson "rwxrwx---", with chmod i do this with octal value "770". If i execute "umask 770" the permissons is not the same with new or copy file. How can i configure this command? I do not understand the "man... (1 Reply)
Discussion started by: Xedrox
1 Replies