如何用sed或awk匹配summer后修改对应行的cotton为light color

原始文件内容 #

$ cat sample1.txt
this is about weather. 
this is summer.   
I drink cold coffee 
I eat Ice-cream
I wear cotton clothes.
this is winter
I drink hot coffee
I eat cake
I wear warm clothes.
this is summer.
I wear cotton sleeveless.
I drink juice.

使用sed实现 #

直接利用sed的区间匹配+替换功能，精准覆盖summer之后到下一个季节之前的内容：

sed '/this is summer\./,/this is /s/cotton/light color/' sample1.txt

逻辑说明 #

• /this is summer\./,/this is /：定义匹配区间——从包含this is summer.的行开始，到下一个以this is 开头的季节行结束
• s/cotton/light color/：在上述区间内，将所有cotton替换为light color

使用awk实现 #

通过标志位控制替换开关，逻辑更灵活，可适配更复杂的场景：

awk '/this is summer\./ {flag=1} /this is / && !/summer/ {flag=0} flag {gsub(/cotton/, "light color")} 1' sample1.txt

逻辑说明 #

1. 匹配到this is summer.时，设置flag=1（开启替换模式）
2. 匹配到其他季节行（this is 开头但非summer）时，设置flag=0（关闭替换模式）
3. 只要flag=1，就用gsub替换当前行的cotton为light color
4. 最后的1表示打印所有行（无论是否修改）

替换后效果 #

执行上述命令后，文件内容会变成：

this is about weather. 
this is summer.   
I drink cold coffee 
I eat Ice-cream
I wear light color clothes.
this is winter
I drink hot coffee
I eat cake
I wear warm clothes.
this is summer.
I wear light color sleeveless.
I drink juice.

内容的提问来源于stack exchange，提问作者meg