Give a QProcess Child Its Proxy Environment

For a downloader launched through QProcess, build the child's environment before starting it:

auto* download = new QProcess(parent);
QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
env.insert("https_proxy", "http://proxy.example:8080");
download->setProcessEnvironment(env);
download->start("curl", {"--head", "https://www.example.com/"});

This Qt fragment assumes an existing parent object, an event loop and curl available to the child. Keep the QProcess alive while it runs, and handle its completion and error signals in the application. For this public-site check with no proxy credentials configured, the HTTP proxy list offers candidate HTTP endpoints for the child’s proxy value.

Starting with systemEnvironment preserves inherited values such as PATH. Constructing an otherwise empty environment and adding one proxy variable would omit those other entries.

The variable name is the key. export is a shell command, not part of that key and not an executable QProcess must launch first. Passing the environment directly also avoids building a shell command around the URL.

setProcessEnvironment applies to the process started afterward. It does not change the environment of an already-running child or the shell that launched the Qt application.

The selected downloader must understand the variable. This example uses lowercase https_proxy for curl's HTTPS request and preserves inherited bypass inputs. Another child program can have another proxy interface.