Custom File Descriptors: An Audit Channel with exec

Every process gets stdin(0), stdout(1), stderr(2) — but you can open more. Use a custom file descriptor to keep an audit log separate from normal output, in one script.

Write /root/scripts/run.sh (assignment in /root/case/assignment.env — TAG, LOG) that:

1. opens fd 3 to the log — exec 3> "$LOG",

2. writes START $TAG to fd 3 (>&3),

3. prints ran $TAG to stdout,

4. writes END $TAG to fd 3,

5. closes fd 3 — exec 3>&-.

The audit lines land in the log; the ran line goes to the terminal — two separate channels. Grading runs the script with your assignment and a held-out one (different TAG and LOG), reads the log, and confirms the audit lines are not on stdout. See /root/case/brief.txt.