du command output

charles@ZentyalCJ:/$ sudo du -sk [a-lo-z]* | sort -n
[sudo] password for charles:

du: cannot access `proc/5574/task/5574/fd/4': No such file or directory
du: cannot access `proc/5574/task/5574/fdinfo/4': No such file or directory
du: cannot access `proc/5574/fd/4': No such file or directory
du: cannot access `proc/5574/fdinfo/4': No such file or directory
0       initrd.img
0       initrd.img.old
0       lib64
0       proc
0       sys
0       vmlinuz
0       vmlinuz.old
4       asterisk
4       cdrom
4       selinux
4       ubuntu
8       Files
12      aquota.group
12      aquota.user
16      build
16      lost+found
52      tmp
256     dev
7932    bin
9868    sbin
12456   lib32
15468   etc
98440   root
136836  opt
148073  boot
1115140 lib
1768404 var
2561856 usr
7239368 srv
11382740        home