Operating Systems – Shell Scripting

Walks $HOME: the ten largest files (asks before deleting), a duplicate-file helper using MD5 (defined in the script, left commented in the default run), cache cleanup, and files not accessed in the last 10 days. The cache clean does not ask first. Do not run this on a machine you care about until you have read the script.

• q01-disk-cleanup.sh

A menu: invert a file’s permissions, search a file (a dot in the pattern means any character), stitch the first N lines of even-positioned files and the last N lines of odd-positioned files into dummy_file.txt, and touch a file if its modification time is more than 24 hours old. Messages are also written to text_file.txt.

• q02-file-utilities.sh

Every 10 seconds it reads the focused X11 window with xdotool, appends a line to ~/app_usage.log, and prints a minutes-and-seconds report. After one minute on a listed app it sends a notification and runs pkill. Needs xdotool (and notify-send for the warning).

• q03-app-usage.sh

You type one word. The parent writes it to input.txt, then for each task it double-forks and the grandchild runs a worker with execlp. Workers append to output.txt (task, PID, result). Option 6 prints that file. Run make so all six binaries sit in the same folder.

• main_file.c
• reverse_str.c
• length_str.c
• ascii_add_2_str.c
• sort_str.c
• capitalize_str.c
• Makefile

A ledger in expenses.csv (date,category,amount). You can add a row, print per-category totals and savings (income minus expenses), print the file, plot spending with gnuplot, and set a budget. A warning appears if expenses go over the budget.

• q05-expense-tracker.sh

A terminal game. The parent is the game manager. Each player and each zombie is a child process and talks through a pipe. After five turns the higher score wins. The zombie count comes from my roll number: (2327 * 3) % 20 + 1, which is 2.

• zombie-survival.cpp
• Makefile

A professor thread and one student thread per person. Students take turns asking a question; the professor waits, answers, and only then is the next student let through. Shared flags are std::atomic — no mutexes or semaphores, as the brief asked.

• office-hours.cpp
• Makefile

You enter batsmen and bowlers. For batting, SJF orders by strike rate and SRTF by average, then a predicted team score is printed. For bowling, SJF uses economy, SRTF uses wickets, and Round Robin rotates bowlers over a number of overs.

• cricket-scheduling.cpp
• Makefile

Four processes, A → B → C → D → A, connected by unnamed pipes. Process A starts a message. Each of B, C and D appends a note, writes its own log file (log_A.txt … log_D.txt), and passes the result on. A prints the fully modified message when it comes back.

• circular-pipes.c
• Makefile

Three queues: Round Robin with quantum 4, Round Robin with quantum 8, then FCFS to completion. You enter each process’s PID, arrival time and burst time. The program prints turnaround time and waiting time.

• mfq-scheduler.cpp
• Makefile