"Escaping" $ when executing a remote bash command from python fabric

Question

So I am trying to automate the set up of an arch linux instance via a python fabric script like this:

from fabric.api import run, sudo

def server_setup_communityrepo():
    run('echo \'echo "[archlinuxfr]" >> /etc/pacman.conf\' | sudo -s')
    run('echo \'echo "Server = http://repo.archlinux.fr/$arch" >> /etc/pacman.conf\' | sudo -s')
    run('echo \'echo " " >> /etc/pacman.conf\' | sudo -s')
    sudo('pacman -Syy yaourt --noconfirm')

The problem occurs on the second run() call because of the $ sign in the $arch. This fabric function fails in line 2 because $ followed by a string is recognized by fabric as a config variable. But I actually want $arch to be understood as a literal in the

echo 'echo "Server = http://repo.archlinux.fr/$arch" >> /etc/pacman.conf' call in bash shell.

How do I "escape" from this fabric quirk and designate the $arch as a literal to be written into my pacman.conf file?

Answer 1

use echo with single quotes. That will prevent the shell from expanding $arch.

run('echo \'Server = http://repo.archlinux.fr/$arch\' | sudo -s tee -a /etc/pacman.conf')

this should be equivalent to

echo 'Server = http://repo.archlinux.fr/$arch' | sudo -s tee -a /etc/pacman.conf

---

quick testing:

>>> import os
>>> os.system('echo \'Server = /foo/$arch\' ')
Server = /foo/$arch
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