Not sure why I am not able to suppress the error message after using /dev/null 2>&1
$ ll /home/harry/workbook/smoel | grep xyz > /dev/null 2>&1 ls: cannot access /home/harry/workbook/smoel: No such file or directory
Answer
The error comes from ls, not grep.
ll /home/harry/workbook/smoel 2>/dev/null | grep xyz