awk帮忙解释 已解决

ncache

data：
Guy Quigley916) 343-6410:250:100:175
Dan Savage406) 298-7744:450:300:275
Nancy McNeil206) 548-1278:250:80:75
John Goldenrod916) 348-4278:250:100:175
Chet Main510) 548-5258:50:95:135
Tom Savage40 926-3456:250:168:200

awk -F: '{m3=($3 >= 200) ? $3 : 0;m4=($4 >= 200) ? $4 : 0;m5=($5 >= 200) ? $5 : 0;  print $1":",m3,m4,m5 }'

打印后面三个月 某个月捐款超过200的就打印  低于200的显示为0
结果

Susan Dalsass: 250 0 0
Archie McNichol: 250 0 0
Jody Savage: 0 0 0
Guy Quigley: 250 0 0
Dan Savage: 450 300 275

之前学习awk的时候做的练习题目,今天翻出来看,发现看不懂了.
请帮忙解释下.

? $3 : 0 什么意思?

[ 本帖最后由 ncache 于 2009-9-1 12:05 编辑 ]

waker

1. 
   
2. 5.12 Conditional Expressions
   
3. 
   
4. A conditional expression is a special kind of expression that has three operands. It allows you to use one expression's value to select one of two other expressions. The conditional expression is the same as in the C language, as shown here:
   
5. 
   
6.      selector ? if-true-exp : if-false-exp
   
7. 
   
8. There are three subexpressions. The first, selector, is always computed first. If it is “true” (not zero or not null), then if-true-exp is computed next and its value becomes the value of the whole expression. Otherwise, if-false-exp is computed next and its value becomes the value of the whole expression. For example, the following expression produces the absolute value of x:
   
9. 
   
10.      x >= 0 ? x : -x
    

复制代码

blackold

条件赋值啰。

ncache

明白了 满足前面的条件就赋值 不满足就赋：后面的值
我都不知道当时是在哪里看的   一点印象都没了

无声无息

你在C中看过吧？或者什么编程基础的书，呵呵