Lab2: add quiz solution

lab2/solution_2.c

@@ -0,0 +1,73 @@
+/*
+ * This code is identical to running
+ * cat $1 | sort | uniq
+ * in bash
+ */
+#include <stdio.h>
+#include <unistd.h>
+
+
+void run_cat(char* filename, int pfd[2]) {
+    dup2(pfd[1], STDOUT_FILENO);
+    close(pfd[0]);
+    close(pfd[1]);
+
+    char cmd[] = "/usr/bin/cat";
+    char *args[] = {"cat", filename, NULL};
+    execve(cmd, args, NULL);
+}
+
+void run_sort(int pfd1[2], int pfd2[2]) {
+    dup2(pfd1[0], STDIN_FILENO);
+    dup2(pfd2[1], STDOUT_FILENO);
+    close(pfd1[0]);
+    close(pfd1[1]);
+    close(pfd2[0]);
+    close(pfd2[1]);
+
+    char cmd[] = "/usr/bin/sort";
+    char *args[] = {"sort", NULL};
+    execve(cmd, args, NULL);
+}
+
+void run_uniq(int pfd[2]) {
+    dup2(pfd[0], STDIN_FILENO);
+    close(pfd[0]);
+    close(pfd[1]);
+
+    char cmd[] = "/usr/bin/uniq";
+    char *args[] = {"uniq", NULL};
+    execve(cmd, args, NULL);
+}
+
+void check_args(int argc, char** argv) {
+    if (argc != 2) {
+        printf("Usage: %s <filename>\n", argv[0]);
+        _exit(1);
+    }
+}
+
+int main(int argc, char** argv) {
+    int pfd1[2];
+    pipe(pfd1);
+
+    int pid = fork();
+
+    if (pid == 0) {
+        run_cat(argv[1], pfd1);
+    } else {
+        close(pfd1[1]);
+
+        int pfd2[2];
+        pipe(pfd2);
+
+        int pid2 = fork();
+
+        if (pid2 == 0) {
+            run_sort(pfd1, pfd2);
+        } else {
+            close(pfd1[0]);
+            run_uniq(pfd2);
+        }
+    }
+}