Linux 'grep' only highlights but doesn't filter

Question

question is in the title.

I'm trying to perform "du -sh * | grep '^[0-9]'" on my root dir to filter out any ... cannot access ..., but my console will just color matches and print out everything.

Thanks for any help

Answer 1

When you run a command, it will always open 3 files: stdin (keyboard input), stdout (command output) and stderr (command output for error messages), these are numbered from 0 to 2.

Those error messages from du are written to stderr, while the normal output is written to stdout. This allows you to redirect the error messages to /dev/null. This makes the error messages disappear, you don't need grep for that.

du -sh * 2>/dev/null