&&与||符号

[dehua@teacher ~]$ [ "$(id -u)" -eq "0" ] && echo you are root || echo you must be root
you must be root
[dehua@teacher ~]$ id -u
501
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&& 与符号
|| 或符号
&&如果前面的命令执行成功则执行&&后的命令否则执行||后面的命令