Why can I not use an exclamation mark in bash' echo, not even when it is escaped?

Question

My question is simple:

$ echo "Hello!"
sh: !": event not found

What is ! in this case? I then tried echo "Match\\!" , but that resolves to Match\\! . How do I have to write the statement?

Answer 1

You can use single quotes:

echo 'Hello!'
Hello!

Otherwise in double quotes shell attempts to expand ! to an event from the history..

Answer 2

您可以使用set +H关闭历史记录扩展，并使用set -H重新启用它