Sed：只修改一些行

Question

In my /etc/apt/sources.list I want to append to all non-comment lines "contrib non-free" using sed.

Here is my expression:

sed -n -i '/^\([^#].*main\)/{s/main/main contrib non-free/p}' /etc/apt/sources.list

It does what I want but it also removes all other lines.

What am I doing wrong?

Answer 1

Problem is with the option -n in your command that suppresses normal output. You need to remove -n and also remove p option from substitution to avoid double printing of matching lines.

This command should work for you:

sed -i '/^\([^#].*main\)/s/main/& contrib non-free/' /etc/apt/sources.list

Answer 2

The accepted answer from @anubhava (thanks for your code, as it pointed me in the right direction) would add contrib non-free even if it already exists in the line. Try the following:

sed -i '/^\([^#].*main\)*$/s/main/& contrib non-free/' /etc/apt/sources.list