最后的结果是5吧

length函数和变量的length属性是两回事，只是恰巧用可一个单词而已
length函数返回字符串去尾部空格后的长度
变量的length属性是该变量存储时需要多少字节(这个记不清了，希望高人指正......)

字符变量的长度属性取决与SAS第一次遇到该变量时所分配给该变量的长度，即SAS构建PDV时给该变量的长度，之后该长度属性不能再变。
而数值型变量在PDV中的长度是一定的（8位），只是输出到数据集中时可以用不同的长度，因此可以在程序的任意位置声明数值型变量的长度。
TRIM函数：If the TRIM function returns a value to a variable that has not yet been assigned a length, by default the variable length is determined by the length of the first argument.

data work.test;
   length city $20; /*Length of variable CITY: 20*/
   city = 'Paris ';
   city2 = trim(city);  /*Length of variable CITY2: 20*/
   city3="paris";  /*Length of variable CITY3: 5*/
   x=3;            /*Length of variable X: 8(default)*/
   y=4;
   length y 4;
   length y 5;   /*Length of variable Y: 5*/
run;

The length statement vs. length function.

The length statement provides descriptive information about variables and use in program compiling phase. It is one of a few non-executable statement.

Length function is just a char function. But the example below deserves to remember,

101  data _null_;
102    x='           ';
103    y=length(x);
104    put x= y=;
105    x='1          ';
106    y=length(x);
107    put x= y=;
108    run;

x=  y=1
x=1 y=1

真正的大牛