DUP and dup2 Functions

DUP and dup2 Functions

Function prototype:

Int DUP (int fd)

Int dup2 (INT oldfd, int newfd)

The DUP and dup2 functions can copy file descriptors.

1. DUP

DUP copies the file descriptor FD and returns the new descriptor, which points to the same file. The new descriptor is the smallest available file descriptor in the system.

2. dup2
Dup2 copies the file descriptor oldfd and can specify newfd as the new descriptor value. If newfd has already pointed to a file, disable it first, and then
Copying.

File descriptors replicated by the DUP and dup2 functions share all file identifiers except the fd_cloexec identifiers.

Return Value:
A new file descriptor is returned. If the file descriptor fails,-1 is returned;