检测是否root身份运行

#!/bin/bash
isRoot()
{
    if [ "$UID" -ne 0 ]
    return 1
    else
    return 0
    fi
}
isRoot
if ["$?" -ne 0 ]
then
    echo "Must be root to run this script"
    exit 1
else
    echo "welcome root user"
    #do something
fi