This section describes how to open a directory stream. All the symbols
are declared in the header file dirent.h.
— Data Type: DIR
The DIR data type represents a directory stream.
You shouldn't ever allocate objects of the struct dirent or
DIR data types, since the directory access functions do that for
you. Instead, you refer to these objects using the pointers returned by
the following functions.
— Function: DIR * opendir (const char *dirname)
The opendir function opens and returns a directory stream for
reading the directory whose file name is dirname. The stream has
type DIR *.
If unsuccessful, opendir returns a null pointer. In addition to
the usual file name errors (see File Name Errors), the
following errno error conditions are defined for this function:
Read permission is denied for the directory named by dirname.
The process has too many files open.
The entire system, or perhaps the file system which contains the
directory, cannot support any additional open files at the moment.
(This problem cannot happen on the GNU system.)
The DIR type is typically implemented using a file descriptor,
and the opendir function in terms of the open function.
See Low-Level I/O. Directory streams and the underlying
file descriptors are closed on exec (see Executing a File).
In some situations it can be desirable to get hold of the file
descriptor which is created by the opendir call. For instance,
to switch the current working directory to the directory just read the
fchdir function could be used. Historically the DIR type
was exposed and programs could access the fields. This does not happen
in the GNU C library. Instead a separate function is provided to allow
— Function: int dirfd (DIR *dirstream)
The function dirfd returns the file descriptor associated with
the directory stream dirstream. This descriptor can be used until
the directory is closed with closedir. If the directory stream
implementation is not using file descriptors the return value is
Published under the terms of the GNU General Public License