请教一个 shell 问题

[SmartDancer]

为何当变量 var 为空时，命令 [ -e $var ] 状态码是 0 ？
thanks

[SoloCompany]

加引号

http://www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html#index-test

The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments.

0 arguments
The expression is false.

1 argument
The expression is true if and only if the argument is not null.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[SmartDancer]

@SoloCompany thank you! 请教一下这个问题如何 google 关键词！