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STATFS(2) System Calls Manual STATFS(2)

statfs, fstatfs
get file system statistics

#include <sys/types.h>
#include <sys/mount.h>

int
statfs(const char *path, struct statfs *buf);

int
fstatfs(int fd, struct statfs *buf);

statfs() returns information about a mounted file system. path is the path name of any file within the mounted file system. buf is a pointer to a statfs structure defined as follows:
typedef struct { int32_t val[2]; } fsid_t;

#define MFSNAMELEN   16 /* length of fs type name, including nul */
#define MNAMELEN     90	/* length of buffer for returned name */

struct statfs {
   u_int32_t       f_flags;        /* copy of mount flags */
   u_int32_t       f_bsize;        /* file system block size */
   u_int32_t       f_iosize;       /* optimal transfer block size */

                                   /* unit is f_bsize */
   u_int64_t       f_blocks;       /* total data blocks in file system */
   u_int64_t       f_bfree;        /* free blocks in fs */
   int64_t         f_bavail;       /* free blocks avail to non-superuser */

   u_int64_t       f_files;        /* total file nodes in file system */
   u_int64_t       f_ffree;        /* free file nodes in fs */
   int64_t         f_favail;       /* free file nodes avail to non-root */

   u_int64_t       f_syncwrites;   /* count of sync writes since mount */
   u_int64_t       f_syncreads;    /* count of sync reads since mount */
   u_int64_t       f_asyncwrites;  /* count of async writes since mount */
   u_int64_t       f_asyncreads;   /* count of async reads since mount */

   fsid_t          f_fsid;         /* file system id */
   u_int32_t       f_namemax;      /* maximum filename length */
   uid_t           f_owner;        /* user that mounted the file system */
   u_int64_t       f_ctime;        /* last mount [-u] time */

   char f_fstypename[MFSNAMELEN];  /* fs type name */
   char f_mntonname[MNAMELEN];     /* directory on which mounted */
   char f_mntfromname[MNAMELEN];   /* mounted file system */
   char f_mntfromspec[MNAMELEN];   /* special for mount request */
   union mount_info mount_info;    /* per-filesystem mount options */
};

fstatfs() returns the same information about an open file referenced by descriptor fd.

Note that f_fsid will be empty unless the user is the superuser.

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

statfs() fails if one or more of the following are true:
[]
A component of the path prefix of path is not a directory.
[]
A component of a pathname exceeded NAME_MAX characters, or an entire pathname (including the terminating NUL) exceeded PATH_MAX bytes.
[]
The file referred to by path does not exist.
[]
Search permission is denied for a component of the path prefix of path.
[]
Too many symbolic links were encountered in translating path.
[]
buf or path points to an invalid address.
[]
An I/O error occurred while reading from or writing to the file system.

fstatfs() fails if one or more of the following are true:

[]
fd is not a valid open file descriptor.
[]
buf points to an invalid address.
[]
An I/O error occurred while reading from or writing to the file system.

df(1), getfsstat(2), mount(2), stat(2)

The statfs() function first appeared in 4.4BSD.
April 27, 2018 OpenBSD-current