getattrlistbulk(2) BSD System Calls Manual getattrlistbulk(2)
NAME
getattrlistbulk -- get file system attributes for multiple directory
entries
SYNOPSIS
#include <sys/attr.h>
#include <unistd.h>
int
getattrlistbulk(int dirfd, struct attrlist * attrList, void * attrBuf,
size_t attrBufSize, uint64_t options);
DESCRIPTION
The getattrlistbulk() function iterates over the items in a directory and
returns information about each directory entry like getattrlist(2).
Note: when getattrlistbulk() returns information about a symbolic link,
the information returned is about the link itself, not the target of the
link.
The function reads directory entries from the directory referenced by the
file descriptor dirfd. The attrList parameter determines what attributes
are returned for each entry. Attributes of those directory entries are
placed into the buffer specified by attrBuf and attrBufSize. The options
parameter allows you to modify the behaviour of the call.
The dirfd parameter must be a file descriptor that references a directory
that you have opened for reading.
The attrList parameter is a pointer to an attrlist structure. All fields
of this structure must be filled before calling the function. See the
discussion of the getattrlist(2) function for a detailed description of
this structure. To get an attribute, the corresponding bit in the appro-
priate attrgroup_t field of the attrlist structure must be set. Volume
attributes cannot be requested but all other supported getattrlist
attributes can be used. For this function, ATTR_CMN_NAME and
ATRR_CMN_RETURNED_ATTRS are required and the absence of these attributes
in the attrList parameter results in an error. Note that not all
attributes supported by getattrlist() may be vended back by this call,
which is why the aforementioned flag must be supplied. In particular
ATTR_CMN_FULLPATH may not be valid on all directory entries whose infor-
mation is requested by this call.
The attrBuf and attrBufSize parameters specify a buffer into which the
function places attribute values. The attributes for any given directory
entry are grouped together and packed in exactly the same way as they are
returned from getattrlist(2) and are subject to exactly the same align-
ment specifications and restrictions. These groups are then placed into
the buffer, one after another. getattrlist(2) should be consulted on
details of the attributes that can be requested for and returned. The
name of the entry itself is provided by the ATTR_CMN_NAME attribute.
Each group starts with a leading uint32_t , which will always be 8-byte
aligned that contains the overall length of the group. You can step from
one group to the next by simply adding this length to your pointer. The
sample code (below) shows how to do this. The initial contents of this
buffer are ignored.
The options parameter is a bit set that controls the behaviour of
getattrlistbulk(). The following option bits are defined.
FSOPT_PACK_INVAL_ATTRS If this is bit is set, then all requested
attributes, even ones that are not supported by
the object or file file system, will be returned
the attrBuf. The attributes actually returned can
be determined by looking at the attribute_set_t
structure returned for the
ATTR_CMN_RETURNED_ATTRS attribute. Default values
will be returned for invalid attributes and
should be ignored.
Please see the discussion of this flag in
getattrlist(2)
If ATTR_CMN_ERROR has been requested and an error specific to a directory
entry occurs, an error will be reported. The ATTR_CMN_ERROR attribute is
a uint32_t which, if non-zero, specifies the error code that was encoun-
tered during the processing of that directory entry. The ATTR_CMN_ERROR
attribute will be after ATTR_CMN_RETURNED_ATTRS attribute in the returned
buffer.
It is typical to ask for a combination of common, file, and directory
attributes and then use the value of the ATTR_CMN_OBJTYPE attribute to
parse the resulting attribute buffer.
A directory which is a mount point for a file system, will have a value
of "DIR_MNTSTATUS_MNTPOINT" set for it's the ATTR_DIR_MOUNTSTATUS
attribute entry. However the attributes for the mount point will be those
from the (underlying) file system. The only way to get the attributes of
mounted root directory is to call getattrlist(2) on the mount point.
RETURN VALUES
Upon successful completion the numbers of entries successfully read is
returned. A value of 0 indicates there are no more entries. Once 0 is
returned, no further entries are returned even if new entries are added
to the directory. Directory iteration should be restarted either by
repostioning the offset to 0 by lseek() or by closing the file descriptor
and opening the directory again. On error, a value of -1 is returned and
errno is set to indicate the error.
When iterating all entries in a directory, getattrlistbulk() is called
repeatedly until a 0 is returned. In such a case if readdir() and
getattrlistbulk() calls on the same fd are mixed, the behavior is unde-
fined.
ERRORS
getattrlistbulk() will fail if:
[EBADF] dirfd is not a valid file descriptor for a directory
open for reading.
[ENOTDIR] The File descriptor dirfd is not a directory.
[EACCES] Search permission is denied on the directory whose
descriptor is given as input.
[EFAULT] attrList or attrBuf points to an invalid address.
[ERANGE] The buffer was too small.
[EINVAL] The bitmapcount field of attrList is not
ATTR_BIT_MAP_COUNT.
[EINVAL] An invalid attribute was requested.
[EINVAL] Volume attributes were requested.
[EINVAL] ATTR_CMN_NAME or ATTR_CMN_RETURNED_ATTRS was not
requested in the attrList parameter.
[EIO] An I/O error occurred while reading from or writing to
the file system.
EXAMPLES
The following code lists the contents of a directory using
getattrlistbulk(). The listing includes the file type.
#include <sys/syscall.h>
#include <sys/attr.h>
#include <sys/errno.h>
#include <sys/vnode.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <assert.h>
#include <stddef.h>
#include <string.h>
#include <stdbool.h>
typedef struct val_attrs {
uint32_t length;
attribute_set_t returned;
uint32_t error;
attrreference_t name_info;
char *name;
fsobj_type_t obj_type;
} val_attrs_t;
void demo(const char *dirpath)
{
int error;
int dirfd;
struct attrlist attrList;
char *entry_start;
char attrBuf[256];
memset(&attrList, 0, sizeof(attrList));
attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
attrList.commonattr = ATTR_CMN_RETURNED_ATTRS |
ATTR_CMN_NAME |
ATTR_CMN_ERROR |
ATTR_CMN_OBJTYPE;
error = 0;
dirfd = open(dirpath, O_RDONLY, 0);
if (dirfd < 0) {
error = errno;
printf("Could not open directory %s", dirpath);
perror("Error was ");
} else {
for (;;) {
int retcount;
retcount = getattrlistbulk(dirfd, &attrList, &attrBuf[0],
sizeof(attrBuf), 0);
printf("\ngetattrlistbulk returned %d", retcount);
if (retcount == -1) {
error = errno;
perror("Error returned : ");
printf("\n");
break;
} else if (retcount == 0) {
/* No more entries in directory */
error = 0;
break;
} else {
int index;
uint32_t total_length;
char *field;
entry_start = &attrBuf[0];
total_length = 0;
printf(" -> entries returned");
for (index = 0; index < retcount; index++) {
val_attrs_t attrs = {0};
printf("\n Entry %d", index);
printf(" -- ");
field = entry_start;
attrs.length = *(uint32_t *)field;
printf(" Length %d ", attrs.length);
total_length += attrs.length;
printf(" Total Length %d ", total_length);
field += sizeof(uint32_t);
printf(" -- ");
/* set starting point for next entry */
entry_start += attrs.length;
attrs.returned = *(attribute_set_t *)field;
field += sizeof(attribute_set_t);
if (attrs.returned.commonattr & ATTR_CMN_ERROR) {
attrs.error = *(uint32_t *)field;
field += sizeof(uint32_t);
}
if (attrs.returned.commonattr & ATTR_CMN_NAME) {
attrs.name = field;
attrs.name_info = *(attrreference_t *)field;
field += sizeof(attrreference_t);
printf(" %s ", (attrs.name +
attrs.name_info.attr_dataoffset));
}
/* Check for error for this entry */
if (attrs.error) {
/*
* Print error and move on to next
* entry
*/
printf("Error in reading attributes for directory entry %d", attrs.error);
continue;
}
printf(" -- ");
if (attrs.returned.commonattr & ATTR_CMN_OBJTYPE) {
attrs.obj_type = *(fsobj_type_t *)field;
field += sizeof(fsobj_type_t);
switch (attrs.obj_type) {
case VREG:
printf("file ");
break;
case VDIR:
printf("directory ");
break;
default:
printf("obj_type = %-2d ", attrs.obj_type);
break;
}
}
printf(" -- ");
}
}
}
(void)close(dirfd);
}
}
SEE ALSO
getattrlist(2), lseek(2)
HISTORY
A getattrlistbulk() function call appeared in OS X version 10.10
Darwin November 15, 2013 Darwin
Mac OS X 10.12.6 - Generated Sun Oct 29 10:52:43 CDT 2017