STATFS(2) System Calls Manual STATFS(2)

statfs, statfs64, fstatfs, fstatfs64 — get file system statistics

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

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

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

int
(const char *path, struct statfs64 *buf);

int
(int fd, struct statfs64 *buf);

The () routine returns information about a mounted file system. The path argument is the path name of any file or directory within the mounted file system. The buf argument is a pointer to a statfs structure. When the macro _DARWIN_FEATURE_64_BIT_INODE is not defined (see stat(2) for more information on this macro), the statfs structure is defined as:

typedef struct { int32_t val[2]; } fsid_t;

#define MFSNAMELEN      15 /* length of fs type name, not inc. nul */
#define MNAMELEN        90 /* length of buffer for returned name */

struct statfs { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
    short   f_otype;	/* type of file system (reserved: zero) */
    short   f_oflags;	/* copy of mount flags (reserved: zero) */
    long    f_bsize;	/* fundamental file system block size */
    long    f_iosize;	/* optimal transfer block size */
    long    f_blocks;	/* total data blocks in file system */
    long    f_bfree;	/* free blocks in fs */
    long    f_bavail;	/* free blocks avail to non-superuser */
    long    f_files;	/* total file nodes in file system */
    long    f_ffree;	/* free file nodes in fs */
    fsid_t  f_fsid;	/* file system id */
    uid_t   f_owner;	/* user that mounted the file system */
    short   f_reserved1;	/* reserved for future use */
    short   f_type;	/* type of file system (reserved) */
    long    f_flags;	/* copy of mount flags */
    long    f_reserved2[2];	/* reserved for future use */
    char    f_fstypename[MFSNAMELEN]; /* fs type name */
    char    f_mntonname[MNAMELEN];    /* directory on which mounted */
    char    f_mntfromname[MNAMELEN];  /* mounted file system */
    char    f_reserved3;	/* reserved for future use */
    long    f_reserved4[4];	/* reserved for future use */
};

However, when the macro _DARWIN_FEATURE_64_BIT_INODE is defined, the statfs structure is defined as:

#define MFSTYPENAMELEN  16 /* length of fs type name including null */
#define MAXPATHLEN      1024
#define MNAMELEN        MAXPATHLEN

struct statfs { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
    uint32_t    f_bsize;        /* fundamental file system block size */
    int32_t     f_iosize;       /* optimal transfer block size */
    uint64_t    f_blocks;       /* total data blocks in file system */
    uint64_t    f_bfree;        /* free blocks in fs */
    uint64_t    f_bavail;       /* free blocks avail to non-superuser */
    uint64_t    f_files;        /* total file nodes in file system */
    uint64_t    f_ffree;        /* free file nodes in fs */
    fsid_t      f_fsid;         /* file system id */
    uid_t       f_owner;        /* user that mounted the filesystem */
    uint32_t    f_type;         /* type of filesystem */
    uint32_t    f_flags;        /* copy of mount exported flags */
    uint32_t    f_fssubtype;    /* fs sub-type (flavor) */
    char        f_fstypename[MFSTYPENAMELEN];   /* fs type name */
    char        f_mntonname[MAXPATHLEN];        /* directory on which mounted */
    char        f_mntfromname[MAXPATHLEN];      /* mounted filesystem */
    uint32_t    f_reserved[8];  /* For future use */
};

Note that the f_fstypename, f_mntonname, and f_mntfromname fields are also wider in this variant.

Fields that are undefined for a particular file system are set to -1. The () routine returns the same information about an open file referenced by descriptor fd.

These are some of the flags that may be present in the f_flags field.

A read-only filesystem
File system is written to synchronously
Can't exec from filesystem
Setuid bits are not honored on this filesystem
Don't interpret special files
Union with underlying filesysten
File system written to asynchronously
File system is exported
File system is stored locally
Quotas are enabled on this file system
This file system is the root of the file system
File system supports volfs
File system is not appropriate path to user data
VFS will ignore ownership information on filesystem objects
File system was mounted by automounter
File system is journaled
File system should defer writes
MAC support for individual labels
File system supports per-file encrypted data protection

In Mac OS X versions before 10.4, f_iosize is 4096. On these older systems, use MAXBSIZE instead.

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

The statfs() routine fails if one or more of the following are true:

[]
A component of the path prefix of Path is not a directory.
[]
The length of a component of path exceeds {NAME_MAX} characters, or the length of path exceeds {PATH_MAX} characters.
[]
The file or directory 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.

The fstatfs() routine 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.

The statfs64 and fstatfs64 routines are equivalent to their corresponding non-64-suffixed routine, when 64-bit inodes are in effect. They were added before there was support for the symbol variants, and so are now deprecated. Instead of using these, set the _DARWIN_USE_64_BIT_INODE macro before including header files to force 64-bit inode support.

The statfs64 structure used by these deprecated routines is the same as the statfs structure when 64-bit inodes are in effect (see above).

stat(2), getfsstat(2)

The statfs() function first appeared in 4.4BSD. The statfs64() and fstatfs64() first appeared in Max OS X 10.5 (Leopard) and are now deprecated in favor of the corresponding symbol variants.

August 14, 2008 macOS 15.6