狂欢 "not": inverting the exit status of a command

Question

我知道我能做到...

if diff -q $f1 $f2
then
    echo "they're the same"
else
    echo "they're different"
fi

但是如果我想否定我正在检查的条件怎么办？即像这样的东西(这显然不起作用)

if not diff -q $f1 $f2
then
    echo "they're different"
else
    echo "they're the same"
fi

我可以做这样的事情......

diff -q $f1 $f2
if [[ $? > 0 ]]
then
    echo "they're different"
else
    echo "they're the same"
fi

这里我检查的是上一条命令的退出状态是否大于0。不过这样感觉有点别扭。有没有更惯用的方法来做到这一点？

Answer 1

if ! diff -q "$f1" "$f2"; then ...