How to escape $ in sed over ssh command?

Question

I am trying to create a patch that users can use to remotely edit a file in a pre-defined way using sed, and I could do this manually on each computer, but it would take a long time.

The line I am struggling with is as follows:

host=[hostname]
port=[portnum]
ssh -t $host -p $port "cp ~/file1 ~/file1.bak ; sed -i \"s/fcn1('param1', $2)\n/fcn2('param2'):$zoom\n/g\" ~/file1"

This makes a backup of file1 and then edits a line in the file. I actually want to edit more than one line, but this line demonstrates the problems: The command works, provided no $ signs are used within the sed command.

I have tried a number of ways of escaping these $ signs but cannot seem to find one that works. I can use a . wildcard in the find, but obviously not in the replace string.

I would use single quotes for the sed command, in order to avoid expanding the $2, but single quotes are already used inside the command.

Does anyone have any ideas of how to overcome this problem? Thanks in advance for any suggestions!

Answer 1

This should work as well:

ssh -t $host -p $port "cp ~/file1 ~/file1.bak && sed -i \"s/fcn1('param1', \\\$2)/fcn2('param2'):\\\$zoom/g\" file1"

You need 3 back slashes as you have to escape the $ sign in the string passed in the remote bash to sed. And you have to escape that back slash and the $ sign when sending it over via ssh.