The ustat() function returns information about a mounted file system. The dev argument is a device number identifying a device containing a mounted file system (see makedev(3C)). The buf argument is a pointer to a ustat structure that includes the following members:

daddr_t  f_tfree;      /* Total free blocks */
ino_t    f_tinode;     /* Number of free inodes */
char     f_fname[6];   /* Filsys name */
char     f_fpack[6];   /* Filsys pack name */

The f_fname and f_fpack members may not contain significant information on all systems; in this case, these members will contain the null character as the first character.

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The ustat() function will fail if:

ECOMM

The dev argument is on a remote machine and the link to that machine is no longer active.

EFAULT

The buf argument points to an illegal address.

EINTR

A signal was caught during the execution of the ustat() function.

EINVAL

The dev argument is not the device number of a device containing a mounted file system.

ENOLINK

The dev argument refers to a device on a remote machine and the link to that machine is no longer active.

EOVERFLOW

One of the values returned cannot be represented in the structure pointed to by buf.

The statvfs(2) function should be used in favor of ustat().

stat(2), statvfs(2), makedev(3C), lfcompile(5)

The NFS revision 2 protocol does not permit the number of free files to be provided to the client; therefore, when ustat() has completed on an NFS file system, f_tinode is always -1.