Question: I need help with comparing two files in makefile.
I need something like this:

```
if [cmp $(FILE1) $(FILE2)] !=0; than 
 echo "OK" 
else 
 echo "WRONG" 
fi

```

But I am not sure how exactly to do that,
Thanks

Answer: 
**Edit: corrected mistaken use of `-z` to `-eq 0` and added Makefile context help.**

It's really a shell question, not specific to makefiles, but this code would work:

```
cmp -s $(FILE1) $(FILE2)
RETVAL=$?
if [ $RETVAL -eq 0 ]; then 
    echo "SAME" 
else 
    echo "NOT SAME" 
fi

```

In a makefile rule, that would look like:

```
my_compare:
    cmp -s $(FILE1) $(FILE2); \
    RETVAL=$$?; \
    if [ $$RETVAL -eq 0 ]; then \
            echo "SAME"; \
    else \
            echo "NOT SAME"; \
    fi

```
Return code from `diff` command will be 0 if files are identical, and 1 if files differs.