.\"	$OpenBSD: getfsstat.2,v 1.10 1999/06/29 14:09:58 aaron Exp $
.\"	$NetBSD: getfsstat.2,v 1.6 1995/06/29 11:40:44 cgd Exp $
.\"
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.\"	@(#)getfsstat.2	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt GETFSSTAT 2
.Os
.Sh NAME
.Nm getfsstat
.Nd get list of all mounted file systems
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/mount.h>
.Ft int
.Fn getfsstat "struct statfs *buf" "size_t bufsize" "int flags"
.Sh DESCRIPTION
.Fn getfsstat
returns information about all mounted file systems.
.Fa buf
is a pointer to an array of
.Xr statfs 2
structures defined as follows:
.Bd -literal
typedef struct { int32_t val[2]; } fsid_t;

#define MFSNAMELEN   16 /* length of fs type name, including NUL */
#define MNAMELEN     32	/* length of buffer for returned name */

struct statfs {
    u_int32_t  f_flags;       /* copy of mount flags */
    u_int32_t  f_bsize;       /* fundamental file system block size */
    u_int32_t  f_iosize;      /* optimal transfer block size */
    u_int32_t  f_blocks;      /* total data blocks in file system */
    u_int32_t  f_bfree;       /* free blocks in fs */
    u_int32_t  f_bavail;      /* free blocks avail to non-superuser */
    u_int32_t  f_files;       /* total file nodes in file system */
    u_int32_t  f_ffree;       /* free file nodes in fs */
    fsid_t     f_fsid;        /* file system id */
    uid_t      f_owner;       /* user that mounted the file system */
    u_int32_t  f_syncwrites;  /* count of sync writes since mount */
    u_int32_t  f_asyncwrites; /* count of async writes since mount */
    u_int32_t  f_spare[4];    /* spare for later */
    char       f_fstypename[MFSNAMELEN]; /* fs type name */
    char       f_mntonname[MNAMELEN];    /* directory on which mounted */
    char       f_mntfromname[MNAMELEN];  /* mounted file system */
    union mount_info mount_info;         /* per-filesystem mount options */
};
.Ed
.Pp
The buffer is filled with an array of
.Fa statfs
structures, one for each mounted file system
up to the size specified by
.Fa bufsize .
.Pp
If
.Fa buf
is
.Dv NULL ,
.Fn getfsstat
returns just the number of mounted file systems.
.Pp
Normally
.Fa flags
should be specified as
.Dv MNT_WAIT .
If
.Fa flags
is set to
.Dv MNT_NOWAIT ,
.Fn getfsstat
will return the information it has available without requesting
an update from each file system.
Thus, some of the information will be out of date, but
.Fn getfsstat
will not block waiting for information from a file system that is
unable to respond.
.Sh RETURN VALUES
Upon successful completion, the number of
.Fa statfs
structures is returned.
Otherwise, \-1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn getfsstat
fails if one or more of the following are true:
.Bl -tag -width Er
.It Bq Er EFAULT
.Fa buf
points to an invalid address.
.It Bq Er EIO
An
.Tn I/O
error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr statfs 2 ,
.Xr fstab 5 ,
.Xr mount 8
.Sh HISTORY
The
.Fn getfsstat
function first appeared in
.Bx 4.4 .