Manual Pages  — VFS_GETOPT

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 option's 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 option's value. The len argument must match the length of the option's 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_setopt() and vfs_setopt_part() functions copy new data into the option's value. In vfs_setopt(), the len argument must match the length of the option's value exactly (i.e., a larger buffer will still cause vfs_copyout() to fail with EINVAL).

The vfs_setopts() function copies a new string into the option's value. The string, including NUL byte, must be no longer than the option's length.

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() and vfs_setopt() functions return 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.

The vfs_setopts() function returns 0 if the copy was successful, EINVAL if the option was found but the string was too long, and ENOENT if the option was not found.