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 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.  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.

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  fol-
       lowing 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  struc-
       ture, 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), fea-
       ture_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)