sed is not showing exit status as other linux commands

Question

$ cat file 
aa
Baa
CaaD
$ sed -i -e 's/aa/AA/' file
$ echo $?
0
$ cat file
AA
BAA
CAAD
$ sed -i -e 's/aa/AA/' file
$ echo $?
0

This sed command exit status in both the cases whether it modifies or not is same and it is returning the same exit status as 0. I would like to have it as 0 if it changes and 1 in case if haven't modified anything.

If grep command return 0 if it found some string and return 1 if it does not , Same way if sed command modifies the file it has to return 0 and sed command doesn't modify anything then it has to return 1

I tried to use sed internal 'q' command but it didn't helped. Please help me.

Answer 1

The answer is "because that's how sed is implemented"

If you want to see if any changes were made

sed -i.bak -e 's/aa/AA/' file
if diff -q file file.bak >/dev/null; then
    echo no changes
else
    echo something changed
fi