Man Pages – Linux Manual Pages

dup, dup2 – duplicate a file descriptor
USAGE
#include <unistd.h>

int dup(int oldfd);
int dup2(int oldfd, int newfd);

DESCRIPTION
dup() and dup2() create a copy of the file descriptor oldfd.

[...]

closedir – close a directory
USAGE
#include <sys/types.h>

#include <dirent.h>

int closedir(DIR *dir);

DESCRIPTION
The closedir() function closes the directory stream associated with
[...]

open, creat – open and possibly create a file or device
USAGE
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int open(const char *pathname, int flags);
int open(const [...]

close – close a file descriptor
USAGE
#include <unistd.h>

int close(int fd);

DESCRIPTION
close() closes a file descriptor, so that it no longer refers to any
file and may be [...]