Nucleus

diff --git a/task/wait.c b/task/wait.c
new file mode 100644
index 0000000..35ee29a
--- /dev/null
+++ b/task/wait.c
@@ -0,0 +1,36 @@
+/*
+ * This file implements task waiting.  A task may wait for another task to
+ * change state.  While waiting, the current task is blocked.  When the target
+ * process changes state the current task is unblocked and gets any relevant
+ * information from it before releasing it.
+ */
+
+#include <errno.h>
+#include <nucleus/task.h>
+
+/* Wait for a child process to change state */
+pid_t
+waitpid(pid_t pid, int *wstatus, int options)
+{
+	if (wstatus && !verify_access(wstatus, sizeof(int), PROT_WRITE))
+		return -EFAULT;
+
+	Task *task = find_task(pid);
+	if (!task)
+		return -ECHILD;
+	current->target = get(task);
+
+	if (task->state != TERMINATED) {
+		if (!task->wait)
+			task->wait = create_list(&taskType, LIST_NORMAL);
+		block_task(WAITING, task->wait);
+	}
+
+	if (wstatus)
+		*wstatus = task->status;
+
+	put(current->target);
+	current->target = NULL;
+
+	return task->tid;
+}