[SOLVED] How can use invert grep after pipe?

Issue

I want to list directory disk usage in a fileserver. I also want to ignore the error messages. Here is my command:

du -sh * | grep -v "Permission denied" | sort -n

The result still contains the permission denied lines:

du: cannot access './myFile1/': Permission denied
du: cannot access './myFile2/': Permission denied
du: cannot access './myFile3/': Permission denied

What am I doing wrong?

Solution

This is because the "Permission denied" is sent through standard error, not through standard output.

If you don't want this information, just silence it by redirecting stderr to /dev/null:

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

This happens with all these error messages:

$ touch a
$ ls a asfasd
ls: cannot access asfasd: No such file or directory
a
$ ls a asfasd | grep cannot
ls: cannot access asfasd: No such file or directory
$ ls a asfasd 2>/dev/null  
a

Answered By - fedorqui 'SO stop harming'

Answer Checked By - Robin (WPSolving Admin)