linux mkdir function can't authorize full permission

Question

I am testing the mkdir function to create a new directory:

folder =  mkdir("./linux", 511);

or

 folder = mkdir("./linux", 0777);

or

folder = mkdir("./linux", S_IRWXU | S_IRWXG | S_IRWXO);

As you can see, I try to authorize the full permission to the directory but here's what comes up with ls -l | grep linux:

drwxr-xr-x 2 manuzhang manuzhang 4096 2012-01-04 06:53 linux

why can't I authorize write permission for group and others?

Updates:
weird thing, as you guys told me I tried umask. It works with either umask(S_IWGRP) or umask(S_IWOTH) but fails with umask(S_IWGRP | S_IWOTH), any ideas?

Answer 1

From man 2 mkdir:

The argument mode specifies the permissions to use. It is modified by the process's umask in the usual way: the permissions of the created directory are (mode & ~umask & 0777).

I suggest you look at your umask - it is probably set to 0022. Try a chmod post-mkdir.