Updating GetPid.c, because for pid_t you need #include <sys/types.h>

GetPid.c

@@ -1,8 +1,9 @@
 #include <unistd.h>
 #include <stdio.h>
+#include <sys/types.h>
 
 void main(void) {
-  __pid_t id_actual, id_padre;
+  pid_t id_actual, id_padre;
   id_actual = getpid();
   id_padre  = getppid();