AWK的替换函数

1、sub替换函数

[xiaomo@Arch-XIAOMO shell]$ cat awkfile
a b c d
b d l o
j a b v l i w
w v l w e r v l
a w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{sub("a","A",$0);print $0}' awkfile
A b c d
b d l o
j A b v l i w
w v l w e r v l
A w v e a f a w

[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{sub("a","A");print $0}' awkfile
A b c d
b d l o
j A b v l i w
w v l w e r v l
A w v e a f a w

[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{sub(/a/,"A");print $0}' awkfile A b c d
b d l o
j A b v l i w
w v l w e r v l
A w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{sub(/^a/,"A");print $0}' awkfile
A b c d
b d l o
j a b v l i w
w v l w e r v l
A w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

默认替换第一列匹配到的字符串

语法是:sub(替换前的内容(可以使用正则表达式),替换后的内容,替换范围)

下面来替换第五列的字符串

[xiaomo@Arch-XIAOMO shell]$ awk '{sub("a","A",$5);print $0}' awkfile
a b c d
b d l o
j a b v l i w
w v l w e r v l
a w v e A f a w
[xiaomo@Arch-XIAOMO shell]$

2、gsub替换函数

[xiaomo@Arch-XIAOMO shell]$ awk '{gsub("a","A",$0);print $0}' awkfile
A b c d
b d l o
j A b v l i w
w v l w e r v l
A w v e A f A w
[xiaomo@Arch-XIAOMO shell]$
[xiaomo@Arch-XIAOMO shell]$ awk '{gsub("a","A",$1);print $0}' awkfile
A b c d
b d l o
j a b v l i w
w v l w e r v l
A w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{gsub(/a/,"A",$1);print $0}' awkfile
A b c d
b d l o
j a b v l i w
w v l w e r v l
A w v e a f a w

[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{gsub(/^a/,"A");print $0}' awkfile
A b c d
b d l o
j a b v l i w
w v l w e r v l
A w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

看到它们之间的区别没有？

sub是局部替换，也就是替换一行之中第一个匹配到的字符串

gsub是全局替换，所有匹配到的字符串都会替换

下面来点好玩的。

[xiaomo@Arch-XIAOMO shell]$

[xiaomo@Arch-XIAOMO shell]$ awk '{sub($1,"A");print $0}' awkfile
A b c d
A d l o
A a b v l i w
A v l w e r v l
A w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

这样匹配也是局部的。

[xiaomo@Arch-XIAOMO shell]$ awk '{sub($1,"A",$2);print $0}' awkfile
a b c d
b d l o
j a b v l i w
w v l w e r v l
a w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

这里没有匹配到，因为你选择了在第二列进行替换规则，但是匹配的内容在第一列，这样是匹配不到的，记住喔～～～

[xiaomo@Arch-XIAOMO shell]$ awk '{gsub($1,"A");print $0}' awkfile
A b c d
A d l o
A a b v l i w
A v l A e r v l
A w v e A f A w
[xiaomo@Arch-XIAOMO shell]$ awk '{gsub($1,"A",$2);print $0}' awkfile
a b c d
b d l o
j a b v l i w
w v l w e r v l
a w v e a f a w
[xiaomo@Arch-XIAOMO shell]$

当然了，awk还有很多玩法，自己去摸索去吧，我实力也就这点了。

转载于:https://blog.51cto.com/xiaofengmo/1751004