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NAME

       readdir, readdir_r - read a directory

SYNOPSIS

       #include <dirent.h>

       struct dirent *readdir(DIR *dirp);

       int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       readdir_r():
           _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE || _SVID_SOURCE || _POSIX_SOURCE

DESCRIPTION

       The  readdir()  function returns a pointer to a dirent structure representing the next directory entry in
       the directory stream pointed to by dirp.  It returns NULL on reaching the end of the directory stream  or
       if an error occurred.

       On Linux, the dirent structure is defined as follows:

           struct dirent {
               ino_t          d_ino;       /* inode number */
               off_t          d_off;       /* not an offset; see NOTES */
               unsigned short d_reclen;    /* length of this record */
               unsigned char  d_type;      /* type of file; not supported
                                              by all filesystem types */
               char           d_name[256]; /* filename */
           };

       The  only fields in the dirent structure that are mandated by POSIX.1 are: d_name[], of unspecified size,
       with at most NAME_MAX characters preceding the terminating null byte ('\0'); and (as  an  XSI  extension)
       d_ino.   The  other  fields  are unstandardized, and not present on all systems; see NOTES below for some
       further details.

       The data returned by readdir() may be overwritten by subsequent calls to readdir() for the same directory
       stream.

       The readdir_r() function is a reentrant version of readdir().  It reads the next directory entry from the
       directory stream dirp, and returns it in the caller-allocated buffer pointed to by entry.  (See NOTES for
       information  on allocating this buffer.)  A pointer to the returned item is placed in *result; if the end
       of the directory stream was encountered, then NULL is instead returned in *result.

RETURN VALUE

       On success, readdir() returns a pointer to  a  dirent  structure.   (This  structure  may  be  statically
       allocated;  do  not  attempt  to  free(3)  it.)   If  the end of the directory stream is reached, NULL is
       returned and errno is not changed.  If an error occurs, NULL is returned and errno is set appropriately.

       The readdir_r() function returns 0 on success.  On error, it returns  a  positive  error  number  (listed
       under ERRORS).  If the end of the directory stream is reached, readdir_r() returns 0, and returns NULL in
       *result.

ERRORS

       EBADF  Invalid directory stream descriptor dirp.

ATTRIBUTES

   Multithreading (see pthreads(7))
       The readdir() function is not thread-safe.

       The readdir_r() function is thread-safe.

CONFORMING TO

       SVr4, 4.3BSD, POSIX.1-2001.

NOTES

       Only the fields d_name and d_ino are specified in POSIX.1-2001.  The remaining fields  are  available  on
       many,  but  not  all  systems.   Under  glibc,  programs can check for the availability of the fields not
       defined  in  POSIX.1  by  testing  whether  the  macros   _DIRENT_HAVE_D_NAMLEN,   _DIRENT_HAVE_D_RECLEN,
       _DIRENT_HAVE_D_OFF, or _DIRENT_HAVE_D_TYPE are defined.

       The  value  returned  in  d_off  is  the  same  as would be returned by calling telldir(3) at the current
       position in the directory stream.  Be aware that despite its type and name, the d_off field is seldom any
       kind of directory offset on modern filesystems.  Applications should treat this field as an opaque value,
       making no assumptions about its contents; see also telldir(3).

       Other than Linux, the d_type field is available mainly only on BSD systems.  This field makes it possible
       to  avoid  the  expense  of  calling  lstat(2) if further actions depend on the type of the file.  If the
       _BSD_SOURCE feature test macro is defined, then glibc defines the following macro constants for the value
       returned in d_type:

       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.

       If the file type could not be determined, the value DT_UNKNOWN is returned in d_type.

       Currently,  only  some  filesystems  (among  them:  Btrfs,  ext2,  ext3,  and ext4) have full support for
       returning the file type in d_type.  All applications must properly handle a return of DT_UNKNOWN.

       Since POSIX.1 does not specify the size of the d_name field, and other  nonstandard  fields  may  precede
       that  field  within  the dirent structure, portable applications that use readdir_r() should allocate the
       buffer whose address is passed in entry as follows:

           name_max = pathconf(dirpath, _PC_NAME_MAX);
           if (name_max == -1)         /* Limit not defined, or error */
               name_max = 255;         /* Take a guess */
           len = offsetof(struct dirent, d_name) + name_max + 1;
           entryp = malloc(len);

       (POSIX.1 requires that d_name is the last field in a struct dirent.)

SEE ALSO

       getdents(2), read(2), closedir(3), dirfd(3), ftw(3), offsetof(3), opendir(3),  rewinddir(3),  scandir(3),
       seekdir(3), telldir(3)

COLOPHON

       This  page  is  part  of  release 3.54 of the Linux man-pages project.  A description of the project, and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

                                                   2013-06-21                                         READDIR(3)