new "mountpoint" export option.

[nfs-utils.git] / support / misc / mountpoint.c

diff --git a/support/misc/mountpoint.c b/support/misc/mountpoint.c
new file mode 100644 (file)
index 0000000..6d0f34e
--- /dev/null
+++ b/support/misc/mountpoint.c
@@ -0,0 +1,34 @@
+
+/*
+ * check if a given path is a mountpoint 
+ */
+
+#include <string.h>
+#include <malloc.h>
+#include <sys/stat.h>
+
+int
+is_mountpoint(char *path)
+{
+       /* Check if 'path' is a current mountpoint.
+        * Possibly we should also check it is the mountpoint of the 
+        * filesystem holding the target directory, but there doesn't
+        * seem a lot of point.
+        *
+        * We deem it to be a mountpoint if appending a ".." gives a different
+        * device or the same inode number.
+        */
+       char *dotdot;
+       struct stat stb, pstb;
+
+       dotdot = malloc(strlen(path)+4);
+       strcat(strcpy(dotdot, path), "/..");
+       if (lstat(path, &stb) != 0 ||
+           lstat(dotdot, &pstb) != 0)
+               return 0;
+
+       if (stb.st_dev != pstb.st_dev
+           || stb.st_ino == pstb.st_ino)
+               return 1;
+       return 0;
+}