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Opening a Directory Stream

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 section 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 section Low-Level Input/Output. Directory streams and the underlying file descriptors are closed on exec (see section Executing a File).

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