plan9 man page for dup

DUP(2)								System Calls Manual							    DUP(2)

NAME
       dup - duplicate an open file descriptor

SYNOPSIS
       #include <u.h>
       #include <libc.h>

       int dup(int oldfd, int newfd)

DESCRIPTION
       Given  a  file  descriptor, oldfd, referring to an open file, dup returns a new file descriptor referring to the same file.  If newfd is in
       the range of legal file descriptors dup will use that for the new file descriptor (closing any old file associated with newfd); if newfd is
       -1 the system chooses the lowest available file descriptor.

SOURCE
       /sys/src/libc/9syscall

SEE ALSO
       intro(2), dup(3)

DIAGNOSTICS
       Sets errstr.

																	    DUP(2)