Awk gsub and the mysterious “1”

问题

I think it is a more general understanding problem but here is my question: If I run the following command in the terminal:

awk '{gsub("a","H")}1'

on the file marks.txt:

1) Amit Physics 80
2) Rahul Maths 90
3) Shyam Biology 87
4) Kedar English 85
5) Hari History 89

I get the following result:

1) Amit Physics 80
2) RHhul MHths 90
3) ShyHm Biology 87
4) KedHr English 85
5) HHri History 89

But if I run it without that "1", I get nothing.

awk '{gsub("a","H")}'

Why is this one so important and what does it stand for?

Thank you in advance!

回答1:

Awk works on condition { action } expressions where the default action is print $0. When you write 1 as a condition then that is a true condition and so invokes the default action of printing the current record.

来源：https://stackoverflow.com/questions/52502311/awk-gsub-and-the-mysterious-1