Linux--shell errors: syntax error near unexpected token ' ('

Several simple shell programs were written these days, and then all appeared syntax error near unexpected token ' ('

Error, and then it is not possible to check the error, the reason behind Baidu was found:

The previous error program fragment is as follows:

usr=$ (WhoAmI)

dr=$ (PWD)

The following errors are indicated:

Syntax error near unexpected token ' ('

Later only to know that the original is a space between the $ and the left parenthesis, correct the program after the normal operation.

In fact above usr=$ (WhoAmI) equivalent to usr= ' WhoAmI '

Linux--shell errors: syntax error near unexpected token ' ('