ubunto查看tree时The program 'tree' is currently not installed. You can install it by typing: sudo apt i

执行tree时候出现如下错误： 一般apt-get出现这种情况： Reading package lists… Done Building dependency tree Reading state information… Done E: Unable to locate package **** 是没有更新APT库 执行如下代码更新一下就好了： udo apt-get update sudo

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