bsd/man/man2/getattrlistbulk.2

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  17 .\"     @(#)getattrlistbulk.2
  18 .
  19 .Dd November 15, 2013
  20 .Dt GETATTRLISTBULK 2
  21 .Os Darwin
  22 .Sh NAME
  23 .Nm getattrlistbulk
  24 .Nd get file system attributes for multiple directory entries
  25 .Sh SYNOPSIS
  26 .Fd #include <sys/attr.h>
  27 .Fd #include <unistd.h>
  28 .Pp
  29 .Ft int
  30 .Fn getattrlistbulk "int dirfd" "struct attrlist * attrList" "void * attrBuf" "size_t attrBufSize" "uint64_t options"
  31 .
  32 .
  33 .Sh DESCRIPTION
  34 The
  35 .Fn getattrlistbulk
  36 function iterates over the items in a directory and returns information about
  37 each directory entry like
  38 .Xr getattrlist 2 .
  39 Note: when
  40 .Fn getattrlistbulk
  41 returns information about a symbolic link, the information returned is about the link itself, not the target of the link.
  42 .Pp
  43 The function reads directory entries from the directory referenced by the file
  44 descriptor
  45 .Fa dirfd .
  46 The
  47 .Fa attrList
  48 parameter determines what attributes are returned for each entry.
  49 Attributes of those directory entries are placed into the buffer specified by
  50 .Fa attrBuf
  51 and
  52 .Fa attrBufSize .
  53 The
  54 .Fa options
  55 parameter allows you to modify the behaviour of the call.
  56 .Pp
  57 .
  58 .Pp
  59 .
  60 .\" dirfd parameter
  61 .
  62 The
  63 .Fa dirfd
  64 parameter must be a file descriptor that references a directory that you have opened for reading.
  65 .Pp
  66 .
  67 .\" attrList parameter
  68 .
  69 The
  70 .Fa attrList
  71 parameter is a pointer to an
  72 .Vt attrlist
  73 structure.
  74 All fields of this structure must be filled before calling the function.
  75 See the discussion of the
  76 .Xr getattrlist 2
  77 function for a detailed description of this structure.
  78 To get an attribute, the corresponding bit in the appropriate
  79 .Vt attrgroup_t
  80 field of the
  81 .Vt attrlist
  82 structure must be set.
  83 Volume attributes  cannot be requested but all other supported getattrlist attributes can be used. For this function,
  84 .Dv ATTR_CMN_NAME
  85 and
  86 .Dv ATRR_CMN_RETURNED_ATTRS
  87 are required and the absence of these attributes in the attrList parameter results in an error.
  88 .Pp
  89 .
  90 .\" attrBuf and attrBufSize parameters
  91 .
  92 The
  93 .Fa attrBuf
  94 and
  95 .Fa attrBufSize
  96 parameters specify a buffer into which the function places attribute values.
  97 The attributes for any given directory entry are grouped together and
  98 packed in exactly the same way as they are returned from
  99 .Xr getattrlist 2
 100 and are subject to exactly the same alignment specifications
 101 and restrictions. These groups are then placed into the buffer, one after another.
 102 .Xr getattrlist 2 should be consulted on details of the attributes that can be
 103 requested for and returned. The name of the entry itself is provided by the
 104 .Dv ATTR_CMN_NAME
 105 attribute.  Each group starts with a leading
 106 .Vt uint32_t
 107 , which will always be 8-byte aligned that contains the overall length of the group.
 108 You can step from one group to the next by simply adding this length to your pointer.
 109 The sample code (below) shows how to do this.
 110 The initial contents of this buffer are ignored.
 111 .Pp
 112 .
 113 .\" options parameter
 114 .
 115 The
 116 .Fa options
 117 parameter is a bit set that controls the behaviour of
 118 .Fn getattrlistbulk .
 119 The following option bits are defined.
 120 .
 121 .Bl -tag -width FSOPT_PACK_INVAL_ATTRS
 122 .
 123 .It FSOPT_PACK_INVAL_ATTRS
 124 If this is bit is set, then all requested  attributes,
 125 even ones that are not supported by the object or file
 126 file system, will be returned the attrBuf. The attributes
 127 actually returned can be determined by looking at the
 128 attribute_set_t structure returned for the
 129 .Dv ATTR_CMN_RETURNED_ATTRS
 130 attribute. Default values will be returned for invalid
 131 attributes and should be ignored.
 132 .Pp
 133 Please see the discussion of this flag in
 134 .Xr getattrlist 2
 135 .
 136 .El
 137 .Pp
 138 If
 139 .Dv ATTR_CMN_ERROR
 140 has been requested and an error specific to a directory entry occurs,
 141 an error will be reported. The
 142 .Dv ATTR_CMN_ERROR
 143 attribute is a uint32_t which, if non-zero, specifies the error code
 144 that was encountered during the processing of that directory entry. The
 145 .Dv ATTR_CMN_ERROR
 146 attribute will be after
 147 .Dv ATTR_CMN_RETURNED_ATTRS
 148 attribute in the returned buffer.
 149 .Pp
 150 It is typical to ask for a combination of common, file, and directory
 151 attributes and then use the value of the
 152 .Dv ATTR_CMN_OBJTYPE
 153 attribute to parse the resulting attribute buffer.
 154 .
 155 .Sh RETURN VALUES
 156 Upon successful completion the numbers of entries successfully read
 157 is returned. A value of 0 indicates there are no more entries. On error,
 158 a value of -1 is returned and
 159 .Va errno
 160 is set to indicate the error.
 161 .Pp
 162 When iterating all entries in a directory,
 163 .Fn getattrlistbulk
 164 is called repeatedly until a 0 is returned. In such a case if
 165 .Fn readdir
 166 and
 167 .Fn getattrlistbulk
 168 calls on the same fd are mixed, the behavior is undefined.
 169
 170 .Pp
 171 .Sh ERRORS
 172 .Fn getattrlistbulk
 173 will fail if:
 174 .Bl -tag -width Er
 175 .
 176 .It Bq Er EBADF
 177 .Fa dirfd
 178 is not a valid file descriptor for a directory open for reading.
 179 .
 180 .It Bq Er ENOTDIR
 181 The File descriptor
 182 .Fa dirfd
 183 is not a directory.
 184 .
 185 .It Bq Er EACCES
 186 Search permission is denied on the directory whose descriptor is given
 187 as input.
 188 .
 189 .It Bq Er EFAULT
 190 .Fa attrList
 191 or
 192 .Em attrBuf
 193 points to an invalid address.
 194 .
 195 .It Bq Er ERANGE
 196 The buffer was too small.
 197 .
 198 .It Bq Er EINVAL
 199 The
 200 .Fa bitmapcount
 201 field of
 202 .Fa attrList
 203 is not
 204 .Dv ATTR_BIT_MAP_COUNT .
 205 .
 206 .It Bq Er EINVAL
 207 An invalid attribute was requested.
 208 .
 209 .It Bq Er EINVAL
 210 Volume attributes were requested.
 211 .
 212 .It Bq Er EINVAL
 213 .Dv ATTR_CMN_NAME
 214 or
 215 .Dv ATTR_CMN_RETURNED_ATTRS
 216 was not requested in the attrList parameter.
 217 .
 218 .It Bq Er EIO
 219 An I/O error occurred while reading from or writing to the file system.
 220 .El
 221 .Pp
 222 .
 223 .Sh EXAMPLES
 224 .
 225 The following code lists the contents of a directory using
 226 .Fn getattrlistbulk .
 227 The listing includes the file type.
 228 .
 229 .Bd -literal
 230 #include <sys/syscall.h>
 231 #include <sys/attr.h>
 232 #include <sys/errno.h>
 233 #include <sys/vnode.h>
 234 #include <unistd.h>
 235 #include <fcntl.h>
 236 #include <stdio.h>
 237 #include <assert.h>
 238 #include <stddef.h>
 239 #include <string.h>
 240 #include <stdbool.h>
 241
 242 typedef struct val_attrs {
 243     uint32_t          length;
 244     attribute_set_t   returned;
 245     uint32_t          error;
 246     attrreference_t   name_info;
 247     char              *name;
 248     fsobj_type_t      obj_type;
 249 } val_attrs_t;
 250
 251
 252 void demo(const char *dirpath)
 253 {
 254     int error;
 255     int dirfd;
 256     struct attrlist attrList;
 257     char *entry_start;
 258     char attrBuf[256];
 259
 260     memset(&attrList, 0, sizeof(attrList));
 261     attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
 262     attrList.commonattr  = ATTR_CMN_RETURNED_ATTRS |
 263                            ATTR_CMN_NAME |
 264                            ATTR_CMN_ERROR |
 265                            ATTR_CMN_OBJTYPE;
 266
 267     error = 0;
 268     dirfd = open(dirpath, O_RDONLY, 0);
 269     if (dirfd < 0) {
 270         error = errno;
 271         printf("Could not open directory %s", dirpath);
 272         perror("Error was ");
 273     } else {
 274         for (;;) {
 275             int retcount;
 276
 277             retcount = getattrlistbulk(dirfd, &attrList, &attrBuf[0],
 278                                sizeof(attrBuf), 0);
 279             printf("\engetattrlistbulk returned %d", retcount);
 280             if (retcount == -1) {
 281                 error = errno;
 282                 perror("Error returned : ");
 283                 printf("\en");
 284                 break;
 285             } else if (retcount == 0) {
 286                 /* No more entries in directory */
 287                 error = 0;
 288                 break;
 289             } else {
 290                 int    index;
 291                 uint32_t total_length;
 292                 char   *field;
 293
 294                 entry_start = &attrBuf[0];
 295                 total_length = 0;
 296                 printf(" -> entries returned");
 297                 for (index = 0; index < retcount; index++) {
 298                     val_attrs_t    attrs = {0};
 299
 300                     printf("\en Entry %d", index);
 301                     printf("  --  ");
 302                     field = entry_start;
 303                     attrs.length = *(uint32_t *)field;
 304                     printf(" Length %d ", attrs.length);
 305                     total_length += attrs.length;
 306                     printf(" Total Length %d ", total_length);
 307                     field += sizeof(uint32_t);
 308                     printf("  --  ");
 309
 310                     /* set starting point for next entry */
 311                     entry_start += attrs.length;
 312
 313                     attrs.returned = *(attribute_set_t *)field;
 314                     field += sizeof(attribute_set_t);
 315
 316                     if (attrs.returned.commonattr & ATTR_CMN_ERROR) {
 317                         attrs.error = *(uint32_t *)field;
 318                         field += sizeof(uint32_t);
 319                     }
 320
 321                     if (attrs.returned.commonattr & ATTR_CMN_NAME) {
 322                         attrs.name =  field;
 323                         attrs.name_info = *(attrreference_t *)field;
 324                         field += sizeof(attrreference_t);
 325                         printf("  %s ", (attrs.name +
 326                             attrs.name_info.attr_dataoffset));
 327                     }
 328
 329                     /* Check for error for this entry */
 330                     if (attrs.error) {
 331                         /*
 332                          * Print error and move on to next
 333                          * entry
 334                          */
 335                         printf("Error in reading attributes for directory \
 336                                entry %d", attrs.error);
 337                         continue;
 338                     }
 339
 340                     printf("  --  ");
 341                     if (attrs.returned.commonattr & ATTR_CMN_OBJTYPE) {
 342                         attrs.obj_type = *(fsobj_type_t *)field;
 343                         field += sizeof(fsobj_type_t);
 344
 345                         switch (attrs.obj_type) {
 346                             case VREG:
 347                                 printf("file  ");
 348                                 break;
 349                             case VDIR:
 350                                 printf("directory    ");
 351                                 break;
 352                             default:
 353                                 printf("obj_type = %-2d  ", attrs.obj_type);
 354                                 break;
 355                         }
 356                     }
 357                     printf("  --  ");
 358                 }
 359             }
 360         }
 361         (void)close(dirfd);
 362     }
 363 }
 364 .Ed
 365 .Pp
 366 .
 367 .Sh SEE ALSO
 368 .
 369 .Xr getattrlist 2 ,
 370 .Xr lseek 2
 371 .
 372 .Sh HISTORY
 373 A
 374 .Fn getattrlistbulk
 375 function call appeared in OS X version 10.10
 376 .