subprocess — shell out safely

subprocess.run is the modern, safe entry point. Pass a **list** of args (no shell=True) to avoid shell injection.

import subprocess
r = subprocess.run(
    ["echo", "hello"],
    capture_output=True, text=True, check=True,
)
print(r.stdout.strip())  # hello

**Patterns**

• check=True raises on non-zero exit — fail fast.
• capture_output=True, text=True for string stdout/stderr.
• Long output → subprocess.Popen with streaming reads.

> 🧪 Concept-only here — the browser sandbox can't spawn processes.