sed to remove lines starting with 'du`

Question

I intent to check the diskspace with du -s

[root@iz2ze9wve43n2nyuvmsfx5z /]# du -s /* | sort -k 1|sed "/du/d"
du: cannot access ‘/proc/31265/task/31265/fd/4’: No such file or directory
du: cannot access ‘/proc/31265/task/31265/fdinfo/4’: No such file or directory
du: cannot access ‘/proc/31265/fd/4’: No such file or directory
du: cannot access ‘/proc/31265/fdinfo/4’: No such file or directory
0   /bin
0   /dev
0   /lib
0   /lib64
0   /proc
0   /sbin
0   /sys
158784  /boot
16  /lost+found
2458148 /usr
37500   /etc
496 /run
4   /home
4   /media
4   /mnt
4   /opt
4   /srv
534680  /root
568 /tmp
935544  /var

So I start to delete lines containing du

1, sed "/du/d"

[root@iz2ze9wve43n2nyuvmsfx5z /]# du -s /* | sort |sed "/du/d" | head -n 6
du: cannot access ‘/proc/31563/task/31563/fd/4’: No such file or directory
du: cannot access ‘/proc/31563/task/31563/fdinfo/4’: No such file or directory
du: cannot access ‘/proc/31563/fd/4’: No such file or directory
du: cannot access ‘/proc/31563/fdinfo/4’: No such file or directory
0   /bin
0   /dev
0   /lib
0   /lib64
0   /proc
0   /sbin

2,Remove the lines not starting with number sed "/[^\d]*/d"

    [root@iz2ze9wve43n2nyuvmsfx5z /]# du -s /* | sort -k 1|sed "/[^\d]*/d" | head -n 6
    du: cannot access ‘/proc/31612/task/31612/fd/4’: No such file or directory
    du: cannot access ‘/proc/31612/task/31612/fdinfo/4’: No such file or directory
    du: cannot access ‘/proc/31612/fd/4’: No such file or directory
    du: cannot access ‘/proc/31612/fdinfo/4’: No such file or directory

but return the lines I want to delete

3,sed "/\d*/d"

[root@iz2ze9wve43n2nyuvmsfx5z /]# du -s /* | sort -k 1|sed "/\d*/d" | head -n 6
du: cannot access ‘/proc/31703/task/31703/fd/4’: No such file or directory
du: cannot access ‘/proc/31703/task/31703/fdinfo/4’: No such file or directory
du: cannot access ‘/proc/31703/fd/4’: No such file or directory
du: cannot access ‘/proc/31703/fdinfo/4’: No such file or directory

How could I remove the lines containing "du"?

Answer 1

As steeldriver commented, the lines beginning with du: cannot access ... and ending with :No such file or directory are error messages from du; it had enumerated those directories in /proc, but the corresponding process(es) had exited before du got around to summing their "disk" space, causing an error when it tried to access those now non-existent directories.

Thankfully, du emits those errors, as it should, to stderr, so you can intercept them and drop them with:

du -s /* 2>/dev/null | sort -n

I also changed your sort command, on the assumption that you want to sort numerically, with the largest sizes at the end.