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GETDIRENTRIESATTR(2)        BSD System Calls Manual       GETDIRENTRIESATTR(2)

NAME
     getdirentriesattr -- get file system attributes for multiple directory
     entries

SYNOPSIS
     #include <sys/attr.h>
     #include <unistd.h>

     int
     getdirentriesattr(int fd, struct attrlist * attrList, void * attrBuf,
         size_t attrBufSize, unsigned long * count, unsigned long * basep,
         unsigned long * newState, unsigned long options);

DESCRIPTION
     The getdirentriesattr() function reads directory entries and returns
     their attributes (that is, metadata).  You can think of it as a combina-tion combination
     tion of getdirentries(2) and getattrlist(2).  The function reads direc-tory directory
     tory entries from the directory referenced by the file descriptor fd.
     Attributes of those directory entries are placed into the buffer speci-fied specified
     fied by attrBuf and attrBufSize.  The attrList parameter determines what
     attributes are returned for each entry.  The count parameter contains the
     number of directory entries requested and returned.  The basep parameter
     returns the directory offset in a manner similar to getdirentries(2).
     The newState parameter allows you to check whether the directory has been
     modified while you were reading it.  The options parameter lets you con-trol control
     trol specific aspects of the function's behaviour.

     The getdirentriesattr() function is only supported by certain volume for-mat format
     mat implementations.  For maximum compatibility, client programs should
     use high-level APIs (such as the Carbon File Manager) to access file sys-tem system
     tem attributes.  These high-level APIs include logic to emulate file sys-tem system
     tem attributes on volumes that don't support getdirentriesattr().

     The fd 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.  You are
     responsible for filling out all fields of this structure before calling
     the function.  See the discussion of the getattrlist(2) function for a
     detailed description of this structure.  To get an attribute you must set
     the corresponding bit in the appropriate attrgroup_t field of the
     attrlist structure.  You must not request volume attributes.

     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).  These groups are then placed into the
     buffer, one after another.  As each group starts with a leading unsigned
     long 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 sam-ple sample
     ple code (below) shows how to do this.  The initial contents of this
     buffer are ignored.

     The count parameter points to a unsigned long variable.  You should ini-tialise initialise
     tialise this variable to be the number of directory entries for which you
     wish to get attributes.  On return, this variable contains the number of
     directory entries whose attributes have been placed into the attribute
     buffer.  This may be smaller than the number that you requested.

     The basep parameter returns the offset of the last directory entry read,
     in a manner identical to getdirentries(2).  You can use this value to
     reset a directory iteration to a known position using lseek(2).  The ini-tial initial
     tial value of the variable is ignored.

     The newState parameter returns a value that changes if the directory has
     been modified.  If you're iterating through the directory by making
     repeated calls to getdirentriesattr(), you can compare subsequent values
     of newState to determine whether the directory has been modified (and
     thus restart your iteration at the beginning).  The initial value of the
     variable is ignored.

     The options parameter is a bit set that controls the behaviour of
     getdirentriesattr().  The following option bits are defined.

     FSOPT_NOINMEMUPDATE  This tells getdirentriesattr() to return the direc-tory directory
                          tory entries from disk rather than taking the extra
                          step of looking at data structures in-memory which
                          may contain changes that haven't been flushed to
                          disk.

                          This option allowed for specific performance opti-mizations optimizations
                          mizations for specific clients on older systems.  We
                          currently recommend that clients not set this option
                          and that file system implementations ignore it.

     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.

RETURN VALUES
     Upon successful completion a value of 0 or 1 is returned.  The value 0
     indicates that the routine completed successfully.  The value 1 indicates
     that the routine completed successfully and has returned the last entry
     in the directory.  On error, a value of -1 is returned and errno is set
     to indicate the error.

COMPATIBILITY
     Not all volumes support getdirentriesattr().  You can test whether a vol-ume volume
     ume supports getdirentriesattr() by using getattrlist(2) to get the vol-ume volume
     ume capabilities attribute ATTR_VOL_CAPABILITIES, and then testing the
     VOL_CAP_INT_READDIRATTR flag.

     The getdirentriesattr() function has been undocumented for more than two
     years.  In that time a number of volume format implementations have been
     created without a proper specification for the behaviour of this routine.
     You may encounter volume format implementations with slightly different
     behaviour than what is described here.  Your program is expected to be
     tolerant of this variant behaviour.

     If you're implementing a volume format that supports getdirentriesattr(),
     you should be careful to support the behaviour specified by this docu-ment. document.
     ment.

ERRORS
     getdirentriesattr() will fail if:

     [ENOTSUP]          The volume does not support getdirentriesattr().

     [EBADF]            fd is not a valid file descriptor for a directory open
                        for reading.

     [EFAULT]           attrList or attrBuf points to an invalid address.

     [EINVAL]           The bitmapcount field of attrList is not
                        ATTR_BIT_MAP_COUNT.

     [EINVAL]           You requested an invalid attribute.

     [EINVAL]           You requested volume attributes.

     [EINVAL]           The options parameter contains an invalid flag.

     [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
     getdirentriesattr().  The listing includes the file type and creator for
     files.

     #include <assert.h>
     #include <stdio.h>
     #include <stddef.h>
     #include <string.h>
     #include <sys/attr.h>
     #include <sys/errno.h>
     #include <unistd.h>
     #include <sys/vnode.h>
     #include <stdbool.h>
     #include <fcntl.h>

     typedef struct attrlist attrlist_t;

     struct FInfoAttrBuf {
         unsigned long   length;
         attrreference_t name;
         fsobj_type_t    objType;
         char            finderInfo[32];
     };
     typedef struct FInfoAttrBuf FInfoAttrBuf;

     enum {
         kEntriesPerCall = 10
     };

     static int FInfoDemo(const char *dirPath)
     {
         int             err;
         int             junk;
         int             dirFD;
         attrlist_t      attrList;
         unsigned long   index;
         unsigned long   count;
         unsigned long   junkBaseP;
         bool            oldStateValid;
         unsigned long   oldState;
         unsigned long   newState;
         bool            done;
         FInfoAttrBuf *  thisEntry;
         char            attrBuf[kEntriesPerCall * (sizeof(FInfoAttrBuf) + 64)];

         // attrBuf is big enough for kEntriesPerCall entries, assuming that
         // the average name length is less than 64.

         memset(&attrList, 0, sizeof(attrList));
         attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
         attrList.commonattr  =    ATTR_CMN_NAME
                                 | ATTR_CMN_OBJTYPE
                                 | ATTR_CMN_FNDRINFO;

         err = 0;
         dirFD = open(dirPath, O_RDONLY, 0);
         if (dirFD < 0) {
             err = errno;
         }
         if (err == 0) {
             oldStateValid = false;
             done = false;
             do {
                 count = kEntriesPerCall;

                 err = getdirentriesattr(
                     dirFD,
                     &attrList,
                     &attrBuf,
                     sizeof(attrBuf),
                     &count,
                     &junkBaseP,
                     &newState,
                     0
                 );
                 if (err < 0) {
                     err = errno;
                 } else {
                     done = err;
                     err = 0;
                 }

                 if (err == 0) {
                     if (oldStateValid) {
                         if (newState != oldState) {
                             printf("*** Directory has changed\n");
                             oldState = newState;
                         }
                     } else {
                         oldState = newState;
                         oldStateValid = true;
                     }

                     thisEntry = (FInfoAttrBuf *) attrBuf;

                     for (index = 0; index < count; index++) {
                         switch (thisEntry->objType) {
                             case VREG:
                                 printf(
                                     "'%4.4s' '%4.4s' ",
                                     &thisEntry->finderInfo[0],
                                     &thisEntry->finderInfo[4]
                                 );
                                 break;
                             case VDIR:
                                 printf("directory     ");
                                 break;
                             default:
                                 printf(
                                     "objType = %-2d  ",
                                     thisEntry->objType
                                 );
                                 break;
                         }
                         printf(
                             "%s\n",
                             ((char *) &thisEntry->name)
                                 + thisEntry->name.attr_dataoffset
                         );

                         // Advance to the next entry.

                         ((char *) thisEntry) += thisEntry->length;
                     }
                 }
             } while ( err == 0 && ! done );
         }

         if (dirFD != -1) {
             junk = close(dirFD);
             assert(junk == 0);
         }

         return err;
     }

SEE ALSO
     getattrlist(2), getdirentries(2), lseek(2)

HISTORY
     A getdirentriesattr() function call appeared in Darwin 1.3.1 (Mac OS X
     version 10.0).

Darwin                         December 15, 2003                        Darwin