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. Once 0 is returned,
 158 no further entries are returned even if new entries are added to the directory.
 159 Directory iteration should be restarted either by repostioning the offset to 0 by
 160 .Fn lseek
 161 or by closing the file descriptor and opening the directory again. On error,
 162 a value of -1 is returned and
 163 .Va errno
 164 is set to indicate the error.
 165 .Pp
 166 When iterating all entries in a directory,
 167 .Fn getattrlistbulk
 168 is called repeatedly until a 0 is returned. In such a case if
 169 .Fn readdir
 170 and
 171 .Fn getattrlistbulk
 172 calls on the same fd are mixed, the behavior is undefined.
 173
 174 .Pp
 175 .Sh ERRORS
 176 .Fn getattrlistbulk
 177 will fail if:
 178 .Bl -tag -width Er
 179 .
 180 .It Bq Er EBADF
 181 .Fa dirfd
 182 is not a valid file descriptor for a directory open for reading.
 183 .
 184 .It Bq Er ENOTDIR
 185 The File descriptor
 186 .Fa dirfd
 187 is not a directory.
 188 .
 189 .It Bq Er EACCES
 190 Search permission is denied on the directory whose descriptor is given
 191 as input.
 192 .
 193 .It Bq Er EFAULT
 194 .Fa attrList
 195 or
 196 .Em attrBuf
 197 points to an invalid address.
 198 .
 199 .It Bq Er ERANGE
 200 The buffer was too small.
 201 .
 202 .It Bq Er EINVAL
 203 The
 204 .Fa bitmapcount
 205 field of
 206 .Fa attrList
 207 is not
 208 .Dv ATTR_BIT_MAP_COUNT .
 209 .
 210 .It Bq Er EINVAL
 211 An invalid attribute was requested.
 212 .
 213 .It Bq Er EINVAL
 214 Volume attributes were requested.
 215 .
 216 .It Bq Er EINVAL
 217 .Dv ATTR_CMN_NAME
 218 or
 219 .Dv ATTR_CMN_RETURNED_ATTRS
 220 was not requested in the attrList parameter.
 221 .
 222 .It Bq Er EIO
 223 An I/O error occurred while reading from or writing to the file system.
 224 .El
 225 .Pp
 226 .
 227 .Sh EXAMPLES
 228 .
 229 The following code lists the contents of a directory using
 230 .Fn getattrlistbulk .
 231 The listing includes the file type.
 232 .
 233 .Bd -literal
 234 #include <sys/syscall.h>
 235 #include <sys/attr.h>
 236 #include <sys/errno.h>
 237 #include <sys/vnode.h>
 238 #include <unistd.h>
 239 #include <fcntl.h>
 240 #include <stdio.h>
 241 #include <assert.h>
 242 #include <stddef.h>
 243 #include <string.h>
 244 #include <stdbool.h>
 245
 246 typedef struct val_attrs {
 247     uint32_t          length;
 248     attribute_set_t   returned;
 249     uint32_t          error;
 250     attrreference_t   name_info;
 251     char              *name;
 252     fsobj_type_t      obj_type;
 253 } val_attrs_t;
 254
 255
 256 void demo(const char *dirpath)
 257 {
 258     int error;
 259     int dirfd;
 260     struct attrlist attrList;
 261     char *entry_start;
 262     char attrBuf[256];
 263
 264     memset(&attrList, 0, sizeof(attrList));
 265     attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
 266     attrList.commonattr  = ATTR_CMN_RETURNED_ATTRS |
 267                            ATTR_CMN_NAME |
 268                            ATTR_CMN_ERROR |
 269                            ATTR_CMN_OBJTYPE;
 270
 271     error = 0;
 272     dirfd = open(dirpath, O_RDONLY, 0);
 273     if (dirfd < 0) {
 274         error = errno;
 275         printf("Could not open directory %s", dirpath);
 276         perror("Error was ");
 277     } else {
 278         for (;;) {
 279             int retcount;
 280
 281             retcount = getattrlistbulk(dirfd, &attrList, &attrBuf[0],
 282                                sizeof(attrBuf), 0);
 283             printf("\engetattrlistbulk returned %d", retcount);
 284             if (retcount == -1) {
 285                 error = errno;
 286                 perror("Error returned : ");
 287                 printf("\en");
 288                 break;
 289             } else if (retcount == 0) {
 290                 /* No more entries in directory */
 291                 error = 0;
 292                 break;
 293             } else {
 294                 int    index;
 295                 uint32_t total_length;
 296                 char   *field;
 297
 298                 entry_start = &attrBuf[0];
 299                 total_length = 0;
 300                 printf(" -> entries returned");
 301                 for (index = 0; index < retcount; index++) {
 302                     val_attrs_t    attrs = {0};
 303
 304                     printf("\en Entry %d", index);
 305                     printf("  --  ");
 306                     field = entry_start;
 307                     attrs.length = *(uint32_t *)field;
 308                     printf(" Length %d ", attrs.length);
 309                     total_length += attrs.length;
 310                     printf(" Total Length %d ", total_length);
 311                     field += sizeof(uint32_t);
 312                     printf("  --  ");
 313
 314                     /* set starting point for next entry */
 315                     entry_start += attrs.length;
 316
 317                     attrs.returned = *(attribute_set_t *)field;
 318                     field += sizeof(attribute_set_t);
 319
 320                     if (attrs.returned.commonattr & ATTR_CMN_ERROR) {
 321                         attrs.error = *(uint32_t *)field;
 322                         field += sizeof(uint32_t);
 323                     }
 324
 325                     if (attrs.returned.commonattr & ATTR_CMN_NAME) {
 326                         attrs.name =  field;
 327                         attrs.name_info = *(attrreference_t *)field;
 328                         field += sizeof(attrreference_t);
 329                         printf("  %s ", (attrs.name +
 330                             attrs.name_info.attr_dataoffset));
 331                     }
 332
 333                     /* Check for error for this entry */
 334                     if (attrs.error) {
 335                         /*
 336                          * Print error and move on to next
 337                          * entry
 338                          */
 339                         printf("Error in reading attributes for directory \
 340                                entry %d", attrs.error);
 341                         continue;
 342                     }
 343
 344                     printf("  --  ");
 345                     if (attrs.returned.commonattr & ATTR_CMN_OBJTYPE) {
 346                         attrs.obj_type = *(fsobj_type_t *)field;
 347                         field += sizeof(fsobj_type_t);
 348
 349                         switch (attrs.obj_type) {
 350                             case VREG:
 351                                 printf("file  ");
 352                                 break;
 353                             case VDIR:
 354                                 printf("directory    ");
 355                                 break;
 356                             default:
 357                                 printf("obj_type = %-2d  ", attrs.obj_type);
 358                                 break;
 359                         }
 360                     }
 361                     printf("  --  ");
 362                 }
 363             }
 364         }
 365         (void)close(dirfd);
 366     }
 367 }
 368 .Ed
 369 .Pp
 370 .
 371 .Sh SEE ALSO
 372 .
 373 .Xr getattrlist 2 ,
 374 .Xr lseek 2
 375 .
 376 .Sh HISTORY
 377 A
 378 .Fn getattrlistbulk
 379 function call appeared in OS X version 10.10
 380 .