为什么"1"在awk中打​​印当前行? [英] Why does "1" in awk print the current line?

问题描述

在此答案，

awk '$2=="no"{$3="N/A"}1' file

被接受.注意AWK脚本末尾的1.在评论中，答案的作者说

was accepted. Note the 1 at the end of the AWK script. In the comments, the author of the answer said

[1是]显示当前行的一种神秘方式.

[1 is] a cryptic way to display the current line.

我很困惑.怎么运作的?

I'm puzzled. How does that work?

推荐答案

在awk，

由于1始终求值为 true ，因此它将执行默认操作{print $0}，因此打印存储在$0

Since 1 always evaluates to true, it performs default operation {print $0}, hence prints the current line stored in $0

因此，awk '$2=="no"{$3="N/A"}1' file等效于和

awk '$2=="no"{$3="N/A"} {print $0}' file

再次$0是 print 的默认参数，因此您也可以编写

Again $0 is default argument to print, so you could also write

awk '$2=="no"{$3="N/A"} {print}' file

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实际上，您也可以使用任何非零数字或始终评估为 true 的任何条件代替 1

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In-fact you could also use any non-zero number or any condition which always evaluates to true in place of 1

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