docs: update README

.gitignore

@@ -56,3 +56,4 @@ dkms.conf
 
 # Nix related things
 .direnv/
+result*/

README.md

@@ -0,0 +1,3 @@
+# CS 3502 Operating Systems Assignments
+
+This repository contains my work for CS 3502: Operating Systems.

assignment1/default.nix

@@ -0,0 +1,22 @@
+let
+  basic-c = name: { stdenv }:
+    stdenv.mkDerivation {
+      inherit name;
+      src = ./.;
+      buildPhase = ''
+        runHook preBuild
+        gcc part2/${name}.c -o ${name}
+        runHook postBuild
+      '';
+      installPhase = ''
+        runHook preInstall
+        mkdir -p $out/bin
+        install ${name} $out/bin/
+        runHook postInstall
+      '';
+    };
+in {
+  a1-hello = basic-c "hello";
+  a1-employee = basic-c "employee";
+  a1-logwriter = basic-c "logwriter";
+}

assignment1/part2/employee.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <string.h>
+
+int main() {
+  // Character array to store name
+  // In C, strings are arrays of characters ending with '\0'
+  char name[50];
+  int employee_id;
+  float hours_worked;
+
+  printf("OwlTech Employee Registration\n");
+  printf("=============================\n");
+
+  printf("Enter your name: ");
+  // fgets reads a line including spaces
+  // stdin means "standard input" (keyboard)
+  fgets(name, sizeof(name), stdin);
+
+  // Remove newline that fgets includes
+  name[strcspn(name, "\n")] = '\0';
+
+  printf("Enter your employee ID: ");
+  // & means "address of" - scanf needs to know where to store the value
+  scanf("%d", &employee_id);
+  printf("Hours worked this week: ");
+  scanf("%f", &hours_worked);
+
+  printf("\nEmployee Summary:\n");
+  printf("Name: %s\n", name); // %s for string
+  printf("ID: %d\n", employee_id); // %d for integer
+  printf("Hours: %.2f\n", hours_worked); // %.2f for float with 2 decimals
+
+  return 0;
+}

assignment1/part2/hello.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int main() {
+  printf("Welcome to OwlTech Industries!\n");
+  printf("Systems Programming Division\n");
+
+  return 0;
+}

assignment1/part2/logwriter.c

@@ -0,0 +1,39 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+int main() {
+  FILE *logfile; // Pointer to file structure
+  char message[100];
+  time_t current_time;
+
+  // Open file for appending ("a" mode)
+  // "w" would overwrite, "r" would read
+  logfile = fopen("owltech.log", "a");
+
+  // Always check if file opened successfully
+  if (logfile == NULL) {
+    printf("Error: Could not open log file\n");
+    return 1; // Return non-zero to indicate error
+  }
+
+  printf("Enter log message: ");
+  fgets(message, sizeof(message), stdin);
+
+  // Get current time
+  time(&current_time);
+
+  // Write to file with timestamp
+  // fprintf works like printf but writes to a file
+  fprintf(logfile, "[%s] %s", ctime(&current_time), message);
+
+  // Always close files when done
+  fclose(logfile);
+  printf("Log entry saved successfully!\n");
+
+  // Display the log file contents
+  printf("\n--- Current Log Contents ---\n");
+  system("cat owltech.log");
+
+  return 0;
+}

assignment1/test.nix

@@ -0,0 +1 @@
+{}

assignment2/default.nix

@@ -0,0 +1,26 @@
+let
+  basic-c = subdir: name: { stdenv }:
+    stdenv.mkDerivation {
+      inherit name;
+      src = ./.;
+      buildPhase = ''
+        runHook preBuild
+        gcc ${subdir}/${name}.c -o ${name}
+        runHook postBuild
+      '';
+      installPhase = ''
+        runHook preInstall
+        mkdir -p $out/bin
+        install ${name} $out/bin/
+        runHook postInstall
+      '';
+    };
+in {
+  a2-p1-producer = basic-c "part1" "producer";
+  a2-p1-consumer = basic-c "part1" "consumer";
+
+  a2-p2-bidirectional = basic-c "part2" "bidirectional";
+
+  a2-p3-producer = basic-c "part3" "producer";
+  a2-p3-consumer = basic-c "part3" "consumer";
+}

assignment2/part1/consumer.c

@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <getopt.h>
+#include <time.h>
+
+int main(int argc, char *argv[]) {
+  int max_lines = -1; // -1 means unlimited
+  int verbose = 0;
+
+  // Parse arguments (-n max_lines, -v verbose)
+  char opt;
+  while ((opt = getopt(argc, argv, "n:v")) != -1) {
+    switch (opt) {
+    case 'n':
+      max_lines = atoi(optarg); break;
+    case 'v':
+      verbose = 1; break;
+    default:
+      printf("Usage: %s [-n max_lines] [-v]\n", argv[0]);
+      return 1;
+    }
+  }
+
+  // Read from stdin line by line
+  // Count lines and characters
+  // If verbose, echo lines to stdout
+  char buffer[256];
+  int lines = 0;
+  int chars = 0;
+  while (fgets(buffer, sizeof(buffer), stdin) != NULL) {
+    int size = strlen(buffer);
+    if (verbose)
+      fwrite(buffer, sizeof(char), size, stdout);
+    chars += size;
+    if (size > 0 && buffer[size - 1] == '\n')
+      lines++;
+    if (lines == max_lines)
+      break;
+  }
+
+  // Print statistics to stderr
+  fprintf(stderr, "Lines: %d\n", lines);
+
+  return 0;
+}

assignment2/part1/producer.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <getopt.h>
+
+int main(int argc, char *argv[]) {
+  FILE *input = stdin;
+  int buffer_size = 4096;
+
+  // Parse command line arguments
+  // -f filename (optional)
+  // b buffer_size (optional)
+  char opt;
+  while ((opt = getopt(argc, argv, "f:b:")) != -1) {
+    switch (opt) {
+    case 'f':
+      input = fopen(optarg, "r");
+      if (input == NULL) {
+        fprintf(stderr, "Error: Could not open input file\n");
+        return EXIT_FAILURE;
+      }
+      break;
+    case 'b':
+      buffer_size = atoi(optarg); break;
+    default:
+      printf("Usage: %s [-f filename] [-b buffer_size]\n", argv[0]);
+      return 1;
+    }
+  }
+
+  // Allocate buffer
+  char *buffer = malloc(buffer_size);
+
+  // Read from input and write to stdout
+  while (fgets(buffer, buffer_size, input) != NULL) {
+    fwrite(buffer, sizeof(char), strlen(buffer), stdout);
+  }
+
+  // Cleanup
+  free(buffer);
+
+  return 0;
+}

assignment2/part1/test

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+
+echo "Building executables..."
+
+cd "${FLAKE:-$(dirname $0)}"
+if command -v nix; then
+    producer="$(nix build --no-link --print-out-paths .#a2-p1-producer)/bin/producer"
+    consumer="$(nix build --no-link --print-out-paths .#a2-p1-consumer)/bin/consumer"
+else
+    gcc producer.c -o producer
+    gcc consumer.c -o consumer
+    producer="./producer"
+    consumer="./consumer"
+fi
+
+echo -e "\nTEST - Sanity Check"
+
+out="$(seq -s " " 1 10 | "$producer" | "$consumer" -v)"
+if test "$out" = "$(seq -s " " 1 10)"; then
+    echo "SUCCESS"
+fi
+
+echo -e "\nTEST - Smaller Buffer Size"
+
+out="$(seq -s " " 1 10 | "$producer" -b 16 | "$consumer" -v)"
+if test "$out" = "$(seq -s " " 1 10)"; then
+    echo "SUCCESS"
+fi
+
+echo -e "\nTEST - Large External File"
+
+head -c 10000 </dev/urandom | od -An -tx >random.txt
+out="$("$producer" -f random.txt | "$consumer" -v)"
+if test "$out" = "$(cat random.txt)"; then
+    echo "SUCCESS"
+fi
+rm random.txt
+
+
+echo -e "\nTEST - Maximum Lines (5)"
+
+head -c 1000 </dev/urandom | od -An -tx >random.txt
+out="$("$producer" -f random.txt | "$consumer" -v -n 5)"
+if test "$out" = "$(cat random.txt | head -n 5)"; then
+    echo "SUCCESS"
+fi
+rm random.txt

assignment2/part2/bidirectional.c

@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/wait.h>
+
+int main () {
+  int pipe1[2]; // Parent to child
+  int pipe2[2]; // Child to parent
+
+  // Create both pipes
+  if (pipe(pipe1) == -1 || pipe(pipe2) == -1) {
+    fprintf(stderr, "Could not open pipes");
+    return 1;
+  }
+
+  // Fork process
+  pid_t pid = fork();
+
+  if (pid == 0) {
+    // Child process
+
+    // Close unused pipe ends
+    close(pipe1[1]) ; // Close write end of pipe1
+    close(pipe2[0]) ; // Close read end of pipe2
+
+    // Read message, send response
+    char *message = malloc(100);
+    read(pipe1[0], message, 100);
+    printf("%s", message);
+    free(message);
+
+    char response[] = "Response from child to parent\n";
+    write(pipe2[1], response, sizeof(response));
+  } else {
+    // Parent process
+
+    // Close unused pipe ends
+    close(pipe1[0]) ; // Close read end of pipe1
+    close(pipe2[1]) ; // Close write end of pipe2
+
+    // Send message, read response
+    char message[] = "Sending message from parent to child\n";
+    write(pipe1[1], message, sizeof(message));
+
+    char *response = malloc(100);
+    read(pipe2[0], response, 100);
+    printf("%s", response);
+    free(response);
+
+    // Wait for child process to terminate
+    waitpid(pid, NULL, 0);
+  }
+
+  return 0;
+}

assignment2/part2/test

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+echo "Building executable..."
+
+cd "${FLAKE:-$(dirname $0)}"
+if command -v nix; then
+    bidirectional="$(nix build --no-link --print-out-paths .#a2-p2-bidirectional)/bin/bidirectional"
+else
+    gcc bidirectional.c -o bidirectional
+    bidirectional="./bidirectional"
+fi
+
+out="$("$bidirectional")"
+read -r -d '' expected <<EOF
+Sending message from parent to child
+Response from child to parent
+EOF
+if test "$out" = "$expected"; then
+    echo "SUCCESS"
+fi

assignment2/part3/consumer.c

@@ -0,0 +1,88 @@
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <getopt.h>
+#include <time.h>
+
+volatile sig_atomic_t shutdown_flag = 0;
+volatile sig_atomic_t stats_flag = 0;
+
+void handle_sigint(int sig) {
+  shutdown_flag = 1;
+}
+
+void handle_sigusr1(int sig) {
+  stats_flag = 1;
+}
+
+int main(int argc, char *argv[]) {
+  struct sigaction sa_sigint;
+  sa_sigint.sa_handler = handle_sigint;
+  sigemptyset(&sa_sigint.sa_mask);
+  sa_sigint.sa_flags = 0;
+  sigaction(SIGINT, &sa_sigint, NULL);
+
+  struct sigaction sa_sigusr1;
+  sa_sigusr1.sa_handler = handle_sigusr1;
+  sigemptyset(&sa_sigusr1.sa_mask);
+  sa_sigusr1.sa_flags = 0;
+  sigaction(SIGUSR1, &sa_sigusr1, NULL);
+
+  int max_lines = -1; // -1 means unlimited
+  int verbose = 0;
+
+  // Parse arguments (-n max_lines, -v verbose)
+  char opt;
+  while ((opt = getopt(argc, argv, "n:v")) != -1) {
+    switch (opt) {
+    case 'n':
+      max_lines = atoi(optarg); break;
+    case 'v':
+      verbose = 1; break;
+    default:
+      printf("Usage: %s [-n max_lines] [-v]\n", argv[0]);
+      return 1;
+    }
+  }
+
+  clock_t start = clock();
+
+  // Read from stdin line by line
+  // Count lines and characters
+  // If verbose, echo lines to stdout
+  char buffer[256];
+  int lines = 0;
+  int chars = 0;
+  while (fgets(buffer, sizeof(buffer), stdin) != NULL) {
+    int size = strlen(buffer);
+    if (verbose)
+      fwrite(buffer, sizeof(char), size, stdout);
+    chars += size;
+    if (size > 0 && buffer[size - 1] == '\n')
+      lines++;
+    if (lines == max_lines)
+      break;
+
+    // Handle shutdown
+    if (shutdown_flag) {
+      fprintf(stderr, "Cancelled\n");
+      return 1;
+    }
+  }
+
+  // Print statistics to stderr (handle SIGUSR1)
+  if (stats_flag) {
+    clock_t end = clock();
+    double time = ((double)(end - start)) / CLOCKS_PER_SEC;
+    double throughput = (double)chars / 1024.0 / 1024.0 / time;
+    printf("Stats:\n");
+    printf("File Size: %d bytes\n", chars);
+    printf("Total Time: %.3f secs\n", time);
+    printf("Throughput: %.3f MB/s\n", throughput);
+  }
+  fprintf(stderr, "Lines: %d\n", lines);
+
+  return 0;
+}

assignment2/part3/producer.c

@@ -0,0 +1,63 @@
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <getopt.h>
+
+volatile sig_atomic_t shutdown_flag = 0;
+
+void handle_sigint(int sig) {
+  shutdown_flag = 1;
+}
+
+int main(int argc, char *argv[]) {
+  struct sigaction sa;
+  sa.sa_handler = handle_sigint;
+  sigemptyset(&sa.sa_mask);
+  sa.sa_flags = 0;
+  sigaction(SIGINT, &sa, NULL);
+
+  FILE *input = stdin;
+  int buffer_size = 4096;
+
+  // Parse command line arguments
+  // -f filename (optional)
+  // b buffer_size (optional)
+  char opt;
+  while ((opt = getopt(argc, argv, "f:b:")) != -1) {
+    switch (opt) {
+    case 'f':
+      input = fopen(optarg, "r");
+      if (input == NULL) {
+        fprintf(stderr, "Error: Could not open input file\n");
+        return EXIT_FAILURE;
+      }
+      break;
+    case 'b':
+      buffer_size = atoi(optarg); break;
+    default:
+      printf("Usage: %s [-f filename] [-b buffer_size]\n", argv[0]);
+      return 1;
+    }
+  }
+
+  // Allocate buffer
+  char *buffer = malloc(buffer_size);
+
+  // Read from input and write to stdout
+  while (fgets(buffer, buffer_size, input) != NULL) {
+    fwrite(buffer, sizeof(char), strlen(buffer), stdout);
+
+    // Handle shutdown
+    if (shutdown_flag) {
+      fprintf(stderr, "Cancelled\n");
+      return 1;
+    }
+  }
+
+  // Cleanup
+  free(buffer);
+
+  return 0;
+}

assignment2/part3/test

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+echo "Building executables..."
+
+cd "${FLAKE:-$(dirname $0)}"
+if command -v nix; then
+    producer="$(nix build --no-link --print-out-paths .#a2-p3-producer)/bin/producer"
+    consumer="$(nix build --no-link --print-out-paths .#a2-p3-consumer)/bin/consumer"
+else
+    gcc producer.c -o producer
+    gcc consumer.c -o consumer
+    producer="./producer"
+    consumer="./consumer"
+fi
+
+seq 1 10000000 >large.txt
+
+echo -e "\nTEST - Buffer size 1024"
+"$producer" -b 1024 -f large.txt | "$consumer" &
+kill -USR1 "$(pidof consumer)"
+wait "$(jobs -rp)"
+
+echo -e "\nTEST - Buffer size 4096"
+"$producer" -b 4096 -f large.txt | "$consumer" &
+kill -USR1 "$(pidof consumer)"
+wait "$(jobs -rp)"
+
+echo -e "\nTEST - Buffer size 16384"
+"$producer" -b 16384 -f large.txt | "$consumer" &
+kill -USR1 "$(pidof consumer)"
+wait "$(jobs -rp)"
+
+rm large.txt

assignment2/test.nix

@@ -0,0 +1,12 @@
+let
+  bash-test = subdir: { runCommandLocal }:
+    runCommandLocal "${subdir}-test" { FLAKE = ../.; }
+      ''
+        mkdir -p $out/bin
+        install ${subdir}/test $out/bin/
+      '';
+in {
+  a2-p1 = bash-test "part1";
+  a2-p2 = bash-test "part2";
+  a2-p3 = bash-test "part3";
+}

flake.nix

@@ -7,11 +7,25 @@
   };
 
   outputs = { self, nixpkgs, systems, ... }:
-    let eachSystem = nixpkgs.lib.genAttrs (import systems);
+    let
-    in {
+      subdirs = [
-      packages = eachSystem (system:
+        "assignment1"
+        "assignment2"
+      ];
+
+      eachSystem = nixpkgs.lib.genAttrs (import systems);
+
+      importFromSubdirs = file: eachSystem (system:
         let pkgs = nixpkgs.legacyPackages.${system};
-        in {});
+        in pkgs.lib.mergeAttrsList
+          (builtins.map (d:
+            builtins.mapAttrs
+              (_: v: pkgs.callPackage v {})
+              (import ./${d}/${file}))
+            subdirs));
+    in {
+      packages = importFromSubdirs "default.nix";
+      checks = importFromSubdirs "test.nix";
 
       devShells = eachSystem (system:
         let pkgs = nixpkgs.legacyPackages.${system};

shell.nix

@@ -1,2 +1,4 @@
-{ pkgs }:
+{ mkShell }:
-pkgs.mkShell {}
+
+# GCC is provided by default
+mkShell {}