Operating Systems — Assignments 2–4

Course: Operating Systems Semester: 3rd Main Attributor: Marinos Matthaiou — inf2023004

Overview

Three assignments exploring core Unix/Linux operating system concepts in C, developed and tested on Ubuntu 24.04.1.

#	Topic	Folder
2	File copying via standard I/O vs. low-level system calls (read/write) with custom buffer size	Ergasia2_mycp/
3	Inter-process communication via pipes, fork, and execlp	Ergasia3_pipe/
4	Process synchronization with semaphores and shared memory (mmap)	Ergasia4_processes/

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Assignment 2 — mycp: Custom File Copy Utility

A cp-like utility comparing two copy strategies:

• Standard I/O — byte-by-byte copy using fgetc/fputc
• Low-level system calls — read/write with a user-specified buffer size

Execution time for each approach is measured and logged to report.out.

Build & run:

cd Ergasia2_mycp
make
./mycp -b<buffer_size> file1 file2   # custom buffer size via system calls
./mycp file1 file2                    # standard I/O

Files:

• mycp.c — implementation
• Makefile — build script
• Manual_Ergasia2.pdf — usage manual
• Report_Ergasia2.pdf — full written report
• report.out — sample timing results from a run
• typescript — recorded terminal session demonstrating execution

Assignment 3 — Pipe-based Inter-Process Communication

Uses pipe(), fork(), dup2(), and execlp() to run the Unix cut -c5- command in a child process, redirect its output through a pipe, and read the result in the parent process.

Build & run:

cd Ergasia3_pipe
make
./helper file1

Files:

• helper.c — implementation
• Makefile — build script
• Manual_Ergasia3.pdf — usage manual
• Report_Ergasia3.pdf — full written report
• typescript — recorded terminal session demonstrating execution

Assignment 4 — Synchronized Multi-Process Printing

Spawns 4 child processes (P1–P4) that take turns printing characters (A–D) in a coordinated cyclic pattern, synchronized via a named semaphore and a shared memory segment (mmap). Output is written both to the console and to output.txt. Signal handlers (SIGINT/SIGTERM) ensure proper cleanup of the semaphore and shared memory on exit.

Build & run:

cd Ergasia4_processes
make
./process
# Press Ctrl+C to stop — the process runs in an infinite loop by design

Files:

• process.c — implementation
• Makefile — build script
• Manual_Ergasia4.pdf — usage manual
• Report_Ergasia4.pdf — full written report
• output_sample.txt — truncated sample of the output (the full run is unbounded)

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Tools / Language

• C (POSIX APIs: pipe, fork, exec, mmap, semaphore.h)
• GNU Make
• Developed and tested on Ubuntu 24.04.1, gcc