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       getdents - get directory entries


       int getdents(unsigned int fd, struct linux_dirent *dirp,
                    unsigned int count);


       This is not the function you are interested in.  Look at readdir(3) for
       the POSIX conforming C library interface.  This page documents the bare
       kernel system call interface.

       The  system  call getdents() reads several linux_dirent structures from
       the directory referred to by the  open  file  descriptor  fd  into  the
       buffer pointed to by dirp.  The argument count is specifies the size of
       that buffer.

       The linux_dirent structure is declared as follows:

           struct linux_dirent {
               unsigned long  d_ino;     /* Inode number */
               unsigned long  d_off;     /* Offset to next linux_dirent */
               unsigned short d_reclen;  /* Length of this linux_dirent */
               char           d_name[];  /* Filename (null-terminated) */
                                   /* length is actually (d_reclen - 2 -
                                      offsetof(struct linux_dirent, d_name) */
               char           pad;       // Zero padding byte */
               char           d_type;    // File type (only since Linux 2.6.4;
                                         // offset is (d_reclen - 1))


       d_ino is an inode number.  d_off is the distance from the start of  the
       directory  to the start of the next linux_dirent.  d_reclen is the size
       of this entire linux_dirent.  d_name is a null-terminated filename.

       d_type is a byte at the end of the structure that  indicates  the  file
       type.  It contains one of the following values (defined in <dirent.h>):

       DT_BLK      This is a block device.

       DT_CHR      This is a character device.

       DT_DIR      This is a directory.

       DT_FIFO     This is a named pipe (FIFO).

       DT_LNK      This is a symbolic link.

       DT_REG      This is a regular file.

       DT_SOCK     This is a Unix domain socket.

       DT_UNKNOWN  The file type is unknown.

       Currently, only some file systems (among them: ext2,  etx3,  and  ext4)
       have  full support returning the file type in d_type.  All applications
       must properly handle a return of DT_UNKNOWN.


       On success, the number of bytes read is returned.  On end of directory,
       0   is   returned.   On  error,  -1  is  returned,  and  errno  is  set


       EBADF  Invalid file descriptor fd.

       EFAULT Argument points outside the calling process’s address space.

       EINVAL Result buffer is too small.

       ENOENT No such directory.

              File descriptor does not refer to a directory.




       Glibc does not provide a wrapper for this system call;  call  it  using
       syscall(2).   You  will  need  to  define  the  linux_dirent  structure

       This call supersedes readdir(2).


       The program below demonstrates the use of  getdents().   The  following
       output  shows an example of what we see when running this program on an
       ext2 directory:

           $ ./a.out /testfs/
           --------------- nread=120 ---------------
           i-node#  file type  d_reclen  d_off   d_name
                  2  directory    16         12  .
                  2  directory    16         24  ..
                 11  directory    24         44  lost+found
                 12  regular      16         56  a
             228929  directory    16         68  sub
              16353  directory    16         80  sub2
             130817  directory    16       4096  sub3

   Program source

       #define HAVE_D_TYPE     /* Remove for kernels < 2.6.4 */
       #define _GNU_SOURCE
       #include <dirent.h>     /* Defines DT_* constants */
       #include <fcntl.h>
       #include <stdio.h>
       #include <unistd.h>
       #include <stdlib.h>
       #include <sys/stat.h>
       #include <sys/syscall.h>

       #define handle_error(msg) \
               do { perror(msg); exit(EXIT_FAILURE); } while (0)

       struct linux_dirent {
           long           d_ino;
           off_t          d_off;
           unsigned short d_reclen;
           char           d_name[];

       #define BUF_SIZE 1024

       main(int argc, char *argv[])
           int fd, nread;
           char buf[BUF_SIZE];
           struct linux_dirent *d;
           int bpos;
       #ifdef HAVE_D_TYPE
           char d_type;

           fd = open(argc > 1 ? argv[1] : ".", O_RDONLY | O_DIRECTORY);
           if (fd == -1)

           for ( ; ; ) {
               nread = syscall(SYS_getdents, fd, buf, BUF_SIZE);
               if (nread == -1)

               if (nread == 0)

               printf("--------------- nread=%d ---------------\n", nread);
               printf("i-node#  file type  d_reclen  d_off   d_name\n");
               for (bpos = 0; bpos < nread;) {
                   d = (struct linux_dirent *) (buf + bpos);
                   printf("%8ld  ", d->d_ino);
       #ifdef HAVE_D_TYPE
                   d_type = *(buf + bpos + d->d_reclen - 1);
                   printf("%-10s ", (d_type == DT_REG) ?  "regular" :
                                    (d_type == DT_DIR) ?  "directory" :
                                    (d_type == DT_FIFO) ? "FIFO" :
                                    (d_type == DT_SOCK) ? "socket" :
                                    (d_type == DT_LNK) ?  "symlink" :
                                    (d_type == DT_BLK) ?  "block dev" :
                                    (d_type == DT_CHR) ?  "char dev" : "???");
                   printf("%4d %10lld  %s\n", d->d_reclen,
                           (long long) d->d_off, (char *) d->d_name);
                   bpos += d->d_reclen;



       readdir(2), readdir(3)


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