feat(lab2): unix lab2 done

Lab 2 is in fact the first lab in the set of ones we actually do. It's
not particularly hard, but consumed some time for me

OSs/lab2/unix/part-A/Makefile

@@ -0,0 +1,17 @@
+targets = father son
+all: $(targets)
+
+father: father.o
+	$(CC) -o $@ $^ $(CFLAGS)
+
+son: son.o
+	$(CC) -o $@ $^ $(CFLAGS)
+
+%.o: %.c
+	$(CC) -c $^ -o $@ $(CFLAGS)
+
+clean:
+	rm -f $(targets)
+	rm -f *.o
+	rm -f task_dump*
+	rm -f task*

OSs/lab2/unix/part-A/README.txt

@@ -0,0 +1,4 @@
+Чтобы продемонстрировать работу лабораторки достаточно запустить lab.sh как
+скрипт. Он соберет проект и запустит его для трех пунктов задания. При этом он
+сложит вывод программы в файлы task0, task1 и task2, а вывод `ps xf` в
+task_dump-0, task_dump-1 и task_dump-2 соотвественно

OSs/lab2/unix/part-A/common.h

@@ -0,0 +1,16 @@
+/*
+ * "THE CHEESE-WARE LICENSE" (Revision 1):
+ * <ElectronixTM> wrote this file. As long as you retain this notice
+ * you can do whatever you want with this stuff. If we meet some day,
+ * and you think this stuff is worth it, you can buy me some cheese
+ * in return
+ */
+
+#ifndef COMMON_H_
+#define COMMON_H_
+
+#define WAIT_FOR_CHILD          0
+#define DONT_WAIT_FOR_CHILD     1
+#define ZOMBIE_PROCESS          2
+
+#endif

OSs/lab2/unix/part-A/father.c

@@ -0,0 +1,56 @@
+/*
+ * "THE CHEESE-WARE LICENSE" (Revision 1):
+ * <ElectronixTM> wrote this file. As long as you retain this notice
+ * you can do whatever you want with this stuff. If we meet some day,
+ * and you think this stuff is worth it, you can buy me some cheese
+ * in return
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <assert.h>
+
+#include "common.h"
+
+#define PROG_PREFIX "father: "
+#define log(fmt, args...) printf(PROG_PREFIX fmt "\n", ##args)
+
+#define CMD_SIZE 256
+
+int main(int argc, const char **argv)
+{
+    if (argc != 2) {
+        log("Wrong program usage. 1 argument shuld be passed - program mode");
+        log("%d - wait for child", WAIT_FOR_CHILD);
+        log("%d - father doesn't wait for child", DONT_WAIT_FOR_CHILD);
+        log("%d - father doesn't wait for child, but child finishes",
+             ZOMBIE_PROCESS);
+        return EXIT_FAILURE;
+    }
+    long mode = strtol(argv[1], NULL, 10);
+    if (fork() == 0) {
+        execl("son", "son", argv[1], NULL);
+    }
+    char cmd[CMD_SIZE] = {0};
+    snprintf(cmd, CMD_SIZE, "ps fx > task_dump-%ld", mode);
+    if (mode == WAIT_FOR_CHILD) {
+        system(cmd);
+        int status = 0;
+        int ret = wait(&status);
+        if (ret < 0) {
+            log("waiting for son ended with error code %d", ret);
+            return EXIT_FAILURE;
+        }
+    } else if (mode == DONT_WAIT_FOR_CHILD) {
+        system(cmd);
+    } else if (mode == ZOMBIE_PROCESS) {
+        sleep(2);
+        system(cmd);
+    } else {
+        log("Invalid argument. No mode correspoiding to %ld", mode);
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}

OSs/lab2/unix/part-A/lab.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+make -j$(nproc)
+
+./father 0 > task0
+./father 1 > task1
+./father 2 > task2

OSs/lab2/unix/part-A/son.c

@@ -0,0 +1,47 @@
+/*
+ * "THE CHEESE-WARE LICENSE" (Revision 1):
+ * <ElectronixTM> wrote this file. As long as you retain this notice
+ * you can do whatever you want with this stuff. If we meet some day,
+ * and you think this stuff is worth it, you can buy me some cheese
+ * in return
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "common.h"
+
+#define PROG_PREFIX "son: "
+#define log(fmt, args...) printf(PROG_PREFIX fmt "\n", ##args)
+
+int main(int argc, const char **argv)
+{
+    log("\n"
+        "HEEEEEY, father\n"
+        "There's an endless road to rediscover\n"
+        "HEEEEEY, sister\n"
+        "Do you still belive in love I wonder");
+    if (argc != 2) {
+        log("Ooops, wrong amount of args, %d", argc);
+        return EXIT_FAILURE;
+    }
+    long mode = strtol(argv[1], NULL, 10);
+    log("mode: %ld", mode);
+    switch(mode) {
+    case WAIT_FOR_CHILD:
+        log("pid %d ppid %d", getpid(), getppid());
+        sleep(5);
+        break;
+    case DONT_WAIT_FOR_CHILD:
+        log("before parent die: pid %d ppid %d", getpid(), getppid());
+        sleep(5);
+        log("after parent die: pid %d ppid %d", getpid(), getppid());
+        break;
+    case ZOMBIE_PROCESS:
+        break;
+    default:
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}