I ask experts to answer the question as a file lock mechanism.

I encountered many problems when writing scripts today. The following are typical examples:

CAT/etc/hosts | uniq>/etc/hosts

CAT/etc/hosts

We will find that the result is the first time there is no problem, but from the second time,/Etc/hosts fileStartBecomes emptyWhat is the specific reason? If you still don't understand it, you can ask the question. The experts say it is a file lock mechanism:

Pipeline commands are not passed to the following command after the previous command is fully executed...
It is executed while passing and reading and writing, and there will certainly be problems!

Solution:

CAT/etc/hosts | uniq>/etc/hosts. tmp

MV/etc/hosts. tmp/etc/hosts

CAT/etc/hosts

 

There are experts downstairs. If you have any supplements, you can also discuss O (strong _ strong) o ha here!