Shell - Suppress output of a single command

Question

I have a rm *.o command in Makefile to remove all the object files generated during compilation. However some error information will be output if some .o file does not exist. So how can I suppress the error information output?

Answer 1

In the context of make, more importantly than the output, you don't want make to treat the result of rm as failure. There are two ways to deal with it:

clean:
    -rm *.o    2> /dev/null
    rm -f *.o  2> /dev/null

The first way is to prefix the command with a minus sign, which tells make to ignore the return code. This is the preferred, make-specific way. The second is to use the -f flag, which is specific only to rm.

On top of that, you can choose to suppress the output with 2> /dev/null or not.

Answer 2

In rare instances, it may also be necessary to redirect the output to /dev/null. You probably want to do rm *.o > /dev/null 2>&1. The > /dev/null part sends stdout to /dev/null and the 2>&1 says to send stderr to wherever stdout is going.