getfsstat.2

早期freebsd实现

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.\"	@(#)getfsstat.2	8.1 (Berkeley) 6/9/93
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.Dd June 9, 1993
.Dt GETFSSTAT 2
.Os
.Sh NAME
.Nm getfsstat
.Nd get list of all mounted filesystems
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/ucred.h>
.Fd #include <sys/mount.h>
.Ft int
.Fn getfsstat "struct statfs *buf" "long bufsize" "int flags"
.Sh DESCRIPTION
.Fn Getfsstat
returns information about all mounted filesystems.
.Fa Buf
is a pointer to
.Xr statfs
structures defined as follows:
.Bd -literal
typedef quad fsid_t;

#define MNAMELEN 32	/* length of buffer for returned name */

struct statfs {
    short   f_type;	/* type of filesystem (see below) */
    short   f_flags;	/* copy of mount flags */
    long    f_bsize;	/* fundamental filesystem block size */
    long    f_iosize;	/* optimal transfer block size */
    long    f_blocks;	/* total data blocks in filesystem */
    long    f_bfree;	/* free blocks in fs */
    long    f_bavail;	/* free blocks avail to non-superuser */
    long    f_files;	/* total file nodes in filesystem */
    long    f_ffree;	/* free file nodes in fs */
    fsid_t  f_fsid;	/* filesystem id */
    long    f_spare[6];	/* spare for later */
    char    f_mntonname[MNAMELEN]; /* directory on which mounted */
    char    f_mntfromname[MNAMELEN]; /* mounted filesystem */
};
/*
 * File system types.
 */
#define	MOUNT_UFS	1
#define	MOUNT_NFS	2
#define	MOUNT_PC	3
.Ed
.Pp
Fields that are undefined for a particular filesystem are set to -1.
The buffer is filled with an array of
.Fa fsstat
structures, one for each mounted filesystem
up to the size specified by
.Fa bufsize .
.Pp
If
.Fa buf
is given as NULL,
.Fn getfsstat
returns just the number of mounted filesystems.
.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 filesystem.
Thus, some of the information will be out of date, but
.Fn getfsstat
will not block waiting for information from a filesystem that is
unable to respond.
.Sh RETURN VALUES
Upon successful completion, the number of 
.Fa fsstat
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 EFAULT
.Fa Buf
points to an invalid address.
.It EIO
An
.Tn I/O
error occurred while reading from or writing to the filesystem.
.El
.Sh SEE ALSO
.Xr statfs 2 ,
.Xr fstab 5 ,
.Xr mount 8
.Sh HISTORY
The
.Nm getfsstat
function first appeared in 4.4BSD.