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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  (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.

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)

COLOPHON

       This page is part of release 3.35 of the Linux man-pages project.  A  description  of  the
       project,  and information about reporting bugs, can be found at http://man7.org/linux/man-
       pages/.

                                            2010-09-10                                 READDIR(3)