Linux

I encountered an interesting behavior the other day when trying to use HTTP and/or HTTPS proxy on a GNU/Linux machine. cURL and friends read environment variables called http_proxy and https_proxy. So, you are thinking, if one wants to have “global” proxy settings, one just has to create a new executable file that is only writable by root in /etc/profile.d with content like this: #!/bin/sh export http_proxy=”http://1.2.3.4” export https_proxy=”$http_proxy” However, you might just notice an confusing occurrence when trying to use hostnames like localhost to refer to your own machine. Unfortunately, the priority is given to the proxy setting regardless if the hostname is static (i.e. it is in /etc/hosts) and it resolves to a local IP like 127.0.0.1. It could happen that your proxy will be a bit stupid and resolve localhost to its own (or even a different) IP, and then you will get burned because you want to refer to your computer with it, not the proxy IP. It has potential to especially be confusing if the output will be very similar to what you are expecting. This can happen when e.g. you are trying to set up a simple web server on your machine and the proxy responds with a place holder page. I can confess that I fell into this trap but I will not anymore. ...