This section describes how to open a directory stream. All the symbols are declared in the header file `dirent.h'.
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.
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 section File Name Errors), the
following errno
error conditions are defined for this function:
EACCES
dirname
.
EMFILE
ENFILE
The DIR
type is typically implemented using a file descriptor,
and the opendir
function in terms of the open
function.
See section Low-Level Input/Output. Directory streams and the underlying
file descriptors are closed on exec
(see section 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
access.
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
-1
.
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