import os
import sys
import subprocess

class DiskMonitor:
    def __init__(self, path="/"):
        self.path = path

    def get_free_gb(self):
        try:
            st = os.statvfs(self.path)
            free_bytes = st.f_bavail * st.f_frsize
            return round(free_bytes / (1024**3), 1)
        except Exception:
            return 0.0

    def push_update(self):
        sys.stdout.write(f"{self.get_free_gb()}\n")
        sys.stdout.flush()

if __name__ == "__main__":
    DiskMonitor().push_update()