Parameter Expansion: Split a Path Without External Tools

Every call to basename, dirname, cut, or sed forks a process — Bash can slice strings itself with parameter expansion, no subprocess required. Your input is in /root/case/assignment.env as PATHSPEC (a full file path).

Write /root/scripts/parse.sh. It takes a path as its first argument and, with no argument, falls back to PATHSPEC from the assignment. Using only parameter expansion, it prints:

`

DIR=<directory part>

BASE=<filename, no directory>

STEM=<filename with its last extension removed>

EXT=<the last extension only>

UPPER=<filename uppercased>

`

The extension is whatever follows the last dot in the filename, so report.2025.tgz has STEM=report.2025 and EXT=tgz.

The tools: ${var%pattern} and ${var%%pattern} strip the shortest and longest matching suffix; ${var#pattern} and ${var##pattern} do the same from the front; ${var^^} uppercases. Working out which one gives which field is the exercise.

Grading runs your script on your PATHSPEC and on a path you haven't seen, so it has to compute the parts, not print them. /root/case/brief.txt restates the task.