VFS_GETOPT(9) MidnightBSD Kernel Developer’s Manual VFS_GETOPT(9)


vfs_getopt, vfs_getopts, vfs_flagopt, vfs_scanopt, vfs_copyopt, vfs_filteropt — manipulate mount options and their values


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


vfs_getopt(struct vfsoptlist *opts, const char *name, void **buf, int *len);

char *

vfs_getops(struct vfsoptlist *opts, const char *name, int *error);


vfs_flagopt(struct vfsoptlist *opts, const char *name, u_int *flags, u_int flag);


vfs_scanopt(struct vfsoptlist *opts, const char *name, const char *fmt, ...);


vfs_copyopt(struct vfsoptlist *opts, const char *name, void *dest, int len);


vfs_filteropt(struct vfsoptlist *opts, const char **legal);


The vfs_getopt() function sets buf to point to the value of the named mount option, and sets len to the length of the value if it is not NULL. The buf argument will point to the actual value, and does not need to be freed or released (and probably should not be modified).

The vfs_getopts() function returns the value of the specified option if it is a string (i.e., NUL terminated).

The vfs_flagopt() function determines if an option exists. If the option does exist, and flags is not NULL, flag is added to those already set in flags. If the option does not exist, and flags is not NULL, flag is removed from those already set in flags. An example of typical usage is:

if (vfs_flagopt(mp->mnt_optnew, "wormlike", NULL, 0))

vfs_flagopt(mp->mnt_optnew, "appendok", &(mp->flags), F_APPENDOK);

The vfs_scanopt() function performs a vsscanf(3) with the options value, using the given format, into the specified variable arguments. The value must be a string (i.e., NUL terminated).

The vfs_copyopt() function creates a copy of the options value. The len argument must match the length of the options value exactly (i.e., a larger buffer will still cause vfs_copyout() to fail with EINVAL).

The vfs_filteropt() function ensures that no unknown options were specified. A option is valid if its name matches one of the names in the list of legal names. An option may be prefixed with ’no’, and still be considered valid.


The vfs_getopt() function returns 0 if the option was found; otherwise, ENOENT is returned.

The vfs_getops() function returns the specified option if it is found, and is NUL terminated. If the option was found, but is not NUL terminated, error is set to EINVAL and NULL is returned. If the option was not found, error is set to 0, and NULL is returned.

The vfs_flagopt() function returns 1 if the option was found, and 0 if it was not.

The vfs_scanopt() function returns 0 if the option was not found, or was not NUL terminated; otherwise, the return value of vsscanf(3) is returned. If vsscanf(3) returns 0, it will be returned unchanged; therefore, a return value of 0 does not always mean the option does not exist, or is not a valid string.

The vfs_copyopt() function returns 0 if the copy was successful, EINVAL if the option was found but the lengths did not match, and ENOENT if the option was not found.

The vfs_filteropt() function returns 0 if all of the options are legal; otherwise, EINVAL is returned.


This manual page was written by Chad David 〈davidc@FreeBSD.org〉 and Ruslan Ermilov 〈ru@FreeBSD.org〉.

MidnightBSD 0.3 February 28, 2007 MidnightBSD 0.3