Added common library file.

Author: optiklab

multithreading/Common.h

@@ -0,0 +1,30 @@
+#include <sys/wait.h>
+
+#define EXIT_FAILURE 1
+
+void kill_child_handler(int sig)
+{
+    int status;
+    pid_t done = waitpid(-1, // Any child
+                         &status,
+                         0); // Blocked mode.
+    if (done == -1)
+    {
+        printf("No more child processes.\n");
+    }
+    else
+    {
+        short isNormalTermination = WIFEXITED(status);
+        if (!isNormalTermination ||
+            // WEXITSTATUS should be used only if normal termination = true.
+            (isNormalTermination && WEXITSTATUS(status) != 0))
+        {
+            printf("Zombie for PID -- %d failed.\n", done);
+            exit(EXIT_FAILURE);
+        }
+        else
+        {
+            printf("Zombie for PID -- %d successfully removed.\n", done);
+        }
+    }
+}