Add namespace demo

Signed-off-by: Prashant P Shah <[email protected]>

namespaces/namespaces.c

@@ -0,0 +1,89 @@
+/*
+ * namespace - Namespace demo 
+ *
+ * Written in 2012 by Prashant P Shah <[email protected]>
+ *
+ * To the extent possible under law, the author(s) have dedicated
+ * all copyright and related and neighboring rights to this software
+ * to the public domain worldwide. This software is distributed
+ * without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication
+ * along with this software.
+ * If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#define _GNU_SOURCE
+#include <sys/utsname.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sched.h>
+#include <signal.h>
+#include <wait.h>
+
+#define STACK_SIZE 4096
+
+static char child_stack[STACK_SIZE];
+
+static char newhostname[] = "rambo";
+
+/* Child function */
+static int childFunc(void *arg)
+{
+	struct utsname uts;
+
+	/* Change the hostname in chid namespace */
+	if (sethostname(newhostname, sizeof(newhostname)) == -1) {
+		perror("sethostname in child");
+		return 0;
+	}
+
+	/* Read the hostname in child process */
+	if (uname(&uts) == -1) {
+		perror("uname child");
+		return 0;
+	}
+
+	printf("hostname in child: %s\n", uts.nodename);
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	struct utsname uts;
+	pid_t child_pid;
+
+	/* Create a child process */
+	child_pid = clone(childFunc, child_stack + STACK_SIZE,
+			CLONE_NEWUTS | SIGCHLD, &newhostname);
+
+	/* Check if clone() succeded */
+	if (child_pid == -1) {
+		perror("clone");
+		exit(EXIT_FAILURE);
+	}
+	printf("PID of child created by clone is %ld\n", (long)child_pid);
+
+	sleep(10);
+
+	/* Read the hostname of parent process */
+	if (uname(&uts) == -1) {
+		perror("uname parent");
+		exit(EXIT_FAILURE);
+	}
+
+	printf("hostname in parent: %s\n", uts.nodename);
+
+	/* Wait for child */
+	if (waitpid(child_pid, NULL, 0) == -1) {
+		perror("wait for child");
+		exit(EXIT_FAILURE);
+	}
+
+	printf("child has terminated\n");
+
+	exit(EXIT_SUCCESS);
+}
+