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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;       /* 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
       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: ext2, etx3, 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
       non-standard 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 3.21 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/.

                                  2009-03-30                        READDIR(3)