OS Labs

Exercises for a Betriebssysteme (Operating Systems) course: Bash scripting, process/thread simulation in Java, and a small Kubernetes client in Rust.

Contents

Shell scripts (Bash)

Script	Purpose
calc.sh	Command-line integer calculator. Usage: calc.sh <int> <operator> <int> where operator is one of ADD, SUB, MULT, DIV, MOD, EXP.
nxls.sh	Lists all non-executable regular files in a given directory. Usage: nxls.sh <dir>.
premv.sh	Renames every file starting with a given prefix to use a new prefix instead. Usage: premv.sh <old-prefix> <new-prefix>.
backup.sh	Interactively backs up files matching a suffix into a backup/ folder, asking j/n (yes/no) for each file before copying. Usage: backup.sh <suffix>.
quiz.sh	Simple two-choice quiz loop: asks a question and repeats until one of two accepted answers is given. Usage: quiz.sh "Frage" A1 A2. Exit code 0 if A1 was chosen, 1 if A2 was chosen.

processSimulator/ (Java)

A single-CPU process-scheduling simulator using READY, RUNNING, and BLOCKED states.

• Process.java — represents a process: id, accumulated runtime, and current state.
• ProsessState.java — enum of the three process states.
• Simulator.java — drives a 50-tick simulation with ready, blocked, and one running process, moving processes between the three states each tick (assign, resign, block, unblock) and printing the system state at every step.

ThreadSimulator/ (Java)

A two-thread traffic-light simulation demonstrating Java's wait()/notifyAll() coordination.

• Controller.java — shared, synchronized controller tracking which direction (NORTH_SOUTH / EAST_WEST) has the green light and the phase (RED/YELLOW/GREEN) of each direction.
• LightThread.java — a Thread per direction that waits for its turn to go green, switches phases, sleeps, then hands the green light to the other direction.
• TrafficLightSim.java — entry point; starts both direction threads.

kube-pod-list/ (Rust)

A minimal Kubernetes client that lists pods in the current namespace.

• Reads the local kubeconfig (~/.kube/config) or in-cluster config.
• Uses the kube and k8s-openapi crates (async, via tokio) to list pods and print each pod's name and status phase.
• Build/run with cargo run from inside kube-pod-list/ (requires a reachable Kubernetes cluster/context).

Requirements

• Bash (for the .sh scripts)
• JDK (for processSimulator/ and ThreadSimulator/) — compile with javac *.java inside each folder, then run the file containing main.
• Rust/Cargo (for kube-pod-list/)