opendir - open a directory
DIR *opendir(const char *name));
The opendir() function opens a directory stream correspond-
ing to the directory name, and returns a pointer to the
directory stream. The stream is positioned at the first
entry in the directory.
The opendir() function returns a pointer to the directory
stream or NULL if an error occurred.
Too many file descriptors in use by process.
Too many files are currently open in the system.
Directory does not exist, or name is an empty string.
Insufficient memory to complete the operation.
name is not a directory.
SVID 3, POSIX, BSD 4.3
open(2), readdir(3), closedir(3), seekdir(3), telldir(3),