The syntax on the shell is basically a glance and then used directly

What made me crazy at that time was the comparison of shells. I didn’t expect that there was a problem here

bash: [y: command not found…

After configuring environment variables

 source .bashrc

Bash: [y: command not found…

Check the syntax. The main reason is that there is no ” between [] and the judgment logic in the middle. After adding a space, there is no problem