# Command: python3 sbx.py h-userns --srt -- 'cd /scratch && python /scratch/h.py /scratch/p5.py /scratch/p5.py' (two sequential runs)
## p5.py
import os
for d in ["/tmp","/var/tmp","/dev/shm","/dev/mqueue","/home/nonroot","/tmp/claude","/run","/sandbox","/code"]:
    p=os.path.join(d,"h_marker_x")
    try: prev=open(p).read().strip()
    except Exception as e: prev="none(%s)"%type(e).__name__
    try: open(p,"w").write("seen"); w="WRITABLE"
    except Exception as e: w="denied(%s)"%type(e).__name__
    print(d, "prev=",prev, w)
## output
unshare on PATH: /usr/bin/unshare
===== /scratch/p5.py
/tmp prev= none(FileNotFoundError) denied(OSError)
/var/tmp prev= none(FileNotFoundError) denied(OSError)
/dev/shm prev= none(FileNotFoundError) WRITABLE
/dev/mqueue prev= none(FileNotFoundError) denied(FileNotFoundError)
/home/nonroot prev= none(FileNotFoundError) denied(OSError)
/tmp/claude prev= none(FileNotFoundError) denied(FileNotFoundError)
/run prev= none(FileNotFoundError) denied(OSError)
/sandbox prev= none(FileNotFoundError) denied(OSError)
/code prev= none(FileNotFoundError) denied(OSError)
ERR: None
===== /scratch/p5.py
/tmp prev= none(FileNotFoundError) denied(OSError)
/var/tmp prev= none(FileNotFoundError) denied(OSError)
/dev/shm prev= none(FileNotFoundError) WRITABLE
/dev/mqueue prev= none(FileNotFoundError) denied(FileNotFoundError)
/home/nonroot prev= none(FileNotFoundError) denied(OSError)
/tmp/claude prev= none(FileNotFoundError) denied(FileNotFoundError)
/run prev= none(FileNotFoundError) denied(OSError)
/sandbox prev= none(FileNotFoundError) denied(OSError)
/code prev= none(FileNotFoundError) denied(OSError)
ERR: None
