while :; echo 'wtf'; done;

line 1: syntax error near unexpected token 'done'

well i certainly have no idea what's wrong with this line. I don't think is the while : part, it's supposed to be a while true loop.

CodePudding user response：

The syntax of while allows multiple commands to be executed to test the condition. Those commands are separated from the commands which are conditionally executed by the keyword do. Consider the line:

while true; echo 'wtf'; echo foo; do echo bar; done

The "do" is essential. In the above, 3 commands are unconditionally executed. If echo foo succeeds, then echo bar will be executed and the loop repeats. If echo foo fails, the loop terminates. If done is seen before do, it is a syntax error.