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 −1 the system chooses the lowest available file descriptor.  Otherwise, ­dup will use ­newfd for the new file descriptor (closing any old file associated with newfd). File descriptors are allocated dynamically, so to prevent unwarranted growth of the file descriptor table, ­dup requires that ­newfd be no greater than 20 more than the highest file descriptor ever used by the program. 

SOURCE

­/sys/src/libc/9syscall

SEE ALSO

intro(2), dup(3)

DIAGNOSTICS

Sets errstr.

Plan 9  —  February 14, 2000