How to change column data in Linux, that starts from a specific line

Question

I want to replace the content of my Column 1 with "chr" added into it. But I want this to be added from the 15th line onwards, otherwise it changes the header information.

I used this command:

awk '{$1 = "chr"$1; print}' sample81a.vcf > sample81A.vcf

but like I mentioned,` it is changing the header too.

How to ensure that the "chr" starts only from line 15 of column 1.

Thanks

Answer 1

您可以使用NR>=15条件从第15行开始在{...}内部执行代码：

awk 'NR>=15 {$1 = "chr" $1} 1' sample81a.vcf > sample81A.vcf

Answer 2

尝试以下代码：

$ awk 'BEGIN{count=0}{++count;if(count >= 15)$1="char"$1;print}' sample81a.vcf > sample81A.vcf