MirOS Manual: getdirentries(2)

GETDIRENTRIES(2)           BSD Programmer's Manual            GETDIRENTRIES(2)

NAME

     getdirentries - get directory entries in a filesystem independent format

SYNOPSIS

     #include <dirent.h>

     int
     getdirentries(int fd, char *buf, int nbytes, long *basep);

DESCRIPTION

     getdirentries() reads directory entries from the directory referenced by
     the file descriptor fd into the buffer pointed to by buf, in a filesystem
     independent format. Up to nbytes of data will be transferred. nbytes must
     be greater than or equal to the block size associated with the file (see
     stat(2)). Some filesystems may not support getdirentries() with buffers
     smaller than this size.

     The data in the buffer is a series of dirent structures each containing
     the following entries:

           u_int32_t       d_fileno;
           u_int16_t       d_reclen;
           u_int8_t        d_type;
           u_int8_t        d_namlen;
           char            d_name[MAXNAMLEN + 1]; /* see below */

     The d_fileno entry is a number which is unique for each distinct file in
     the filesystem. Files that are linked by hard links (see link(2)) have
     the same d_fileno. The d_reclen entry is the length, in bytes, of the
     directory record.

     The d_type is the type of file, where the following are possible types:
     DT_UNKNOWN, DT_FIFO, DT_CHR, DT_DIR, DT_BLK, DT_REG, DT_LNK, and DT_SOCK.

     The d_namlen entry specifies the length of the file name excluding the
     NUL byte. Thus the actual size of d_name may vary from 1 to MAXNAMLEN +
     1.

     The d_name entry contains a NUL-terminated file name.

     Entries may be separated by extra space. The d_reclen entry may be used
     as an offset from the start of a dirent structure to the next structure,
     if any.

     Invalid entries with d_fileno set to 0 may be returned among regular en-
     tries.

     The actual number of bytes transferred is returned. The current position
     pointer associated with fd is set to point to the next block of entries.
     The pointer may not advance by the number of bytes returned by getdiren-
     tries().

     getdirentries() writes the position of the block read into the location
     pointed to by basep. Alternatively, the current position pointer may be
     set and retrieved by lseek(2). The current position pointer should only
     be set to a value returned by lseek(2), a value returned in the location
     pointed to by basep, or zero.

RETURN VALUES

     If successful, the number of bytes actually transferred is returned. A
     value of zero is returned when the end of the directory has been reached.
     Otherwise, -1 is returned and the global variable errno is set to indi-
     cate the error.

EXAMPLES

     The following code may be used to iterate on all entries in a directory:

           char *buf, *ebuf, *cp;
           long base;
           size_t bufsize;
           int fd, nbytes;
           char *path;
           struct stat sb;
           struct dirent *dp;

           if ((fd = open(path, O_RDONLY)) < 0)
                   err(2, "cannot open %s", path);
           if (fstat(fd, &sb) < 0)
                   err(2, "fstat");
           bufsize = sb.st_size;
           if (bufsize < sb.st_blksize)
                   bufsize = sb.st_blksize;
           if ((buf = malloc(bufsize)) == NULL)
                   err(2,  "cannot malloc %lu bytes", (unsigned long)bufsize);
           while ((nbytes = getdirentries(fd, buf, bufsize, &base)) > 0) {
                   ebuf = buf + nbytes;
                   cp = buf;
                   while (cp < ebuf) {
                           dp = (struct dirent *)cp;
                           printf("%s\n", dp->d_name);
                           cp += dp->d_reclen;
                   }
           }
           if (nbytes < 0)
                   err(2, "getdirentries");
           free(buf);

ERRORS

     getdirentries() will fail if:

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

     [EFAULT]      Either buf or basep points outside the allocated address
                   space.

     [EINVAL]      The file referenced by fd is not a directory, or nbytes is
                   too small for returning a directory entry or block of en-
                   tries, or the current position pointer is invalid.

     [EIO]         An I/O error occurred while reading from or writing to the
                   file system.

SEE ALSO

     lseek(2), open(2), opendir(3), dirent(5)

HISTORY

     The getdirentries() function first appeared in 4.4BSD.

MirOS BSD #10-current            June 9, 1993                                1

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