Help with file editing in Linux? (Without a text editor)

Hi all,
I am currently trying to edit a conf file within a docker container, however, the people that have made it have not preinstalled any text editors with it. When I get into the container, I am logged in as root, however, apt does not find any packages from the typical repositories. So here is the dilema. I need to add a couple of IPs within the file (each on a separate line), but can't find a way to do it. I thought that using the echo "ip_address" >> file_name.php would work, but I don't know if it is possible to specify the row on which the IP should be added.

Here is the snipped from the file I am talking about:

'trusted_domains' =>
array (
0 => '192.168.88.62:8080',
),

 

Vi is normally available but I am not used to it. Nano is easier but it may not be installed. Anyway, try installing nano or learn to use vi.

 

Make sure there really is no text editor. Try commands

Code:

editor
vi
vim

If there are no editors, I suspect what @Jesse Norell wrote is true.
You are correct that >> appends to the end of the file, so you can add new last line, but not in the middle. You could get creative with commands head and tail and snip each line to it's own file, then combine them to one (with cat for example). There is also cut to get parts of a line.
If you have terminal where you can cut and paste, edit on your workstation editor and paste back.

 

I normally want to know what inside my conf file before editing them (cat), back them up (cp), use proper editor and won't take a risk of overriding it with such commands. In any event, I found this topic which teach on how to install app inside docker: How to Install, Run and Delete Applications Inside Docker Containers. I hope it is useful to you.

 

Thank you for the answers, everyone. To be honest, the answer was extremely simple :-D. It turns out the repositories are not updated inside the container, so in order to install an editor I had to update the repositories with apt update. Though it took me 5 hours to find that in a random video on YouTube ... ( I feel so dumb). Anyway, on topic, I tried using the traditional GNU commands (cat, cp, head, tail, etc.) but either I am not creative enough or don't know them well enough. Can anyone give an example of the way they can be used to achieve the goal?

 

sed '# i text string to be inserted' file_name.php

# is the line number you want the text inserted on.
i is the instruction to insert text.

so to insert an ip and port number on line 15 of the file connection.txt:

sed '15 i 192.168.1.13:443' connection.txt