add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/update.c

@@ -0,0 +1,34 @@
+/* update - do sync periodically		Author: Andy Tanenbaum */
+
+#include <sys/types.h>
+#include <signal.h>
+
+main()
+{
+  int fd, buf[2];
+
+
+  /* Disable SIGTERM */
+  signal(SIGTERM, SIG_IGN);
+
+  /* Release all (?) open file descriptors. */
+  close(0);
+  close(1);
+  close(2);
+
+  /* Release current directory to avoid locking current device. */
+  chdir("/");
+
+  /* Open some files to hold their inodes in core. */
+/*open("/bin", 0);*/
+/*open("/lib", 0);*/
+/*open("/etc", 0);*/
+/*open("/tmp", 0);*/
+
+
+  /* Flush the cache every 30 seconds. */
+  while (1) {
+	sync();
+	sleep(30);
+  }
+}