READDIR(3)                                          Linux Programmer's Manual                                         READDIR(3)



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;       /* offset to the next dirent */
               unsigned short d_reclen;    /* length of this record */
               unsigned char  d_type;      /* type of file; not supported
                                              by all file system 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; and (as an XSI extension) d_ino.  The other fields are unstan-
       dardized, 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.  If the end of the direc-
       tory stream is reached, readdir_r() returns 0, and returns NULL in *result.

ERRORS
       EBADF  Invalid directory stream descriptor dirp.

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.

       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 file systems (among them: Btrfs, ext2, ext3, and ext4) have full support 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:

           len = offsetof(struct dirent, d_name) +
                     pathconf(dirpath, _PC_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), feature_test_macros(7)

COLOPHON
       This page is part of release 3.25 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/.



                                                           2009-07-04                                                 READDIR(3)