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* Public domain dup2() lookalike
* by Curtis Jackson @ AT&T Technologies, Burlington, NC
* electronic address: burl!rcj
* dup2 performs the following functions:
* Check to make sure that fd1 is a valid open file descriptor.
* Check to see if fd2 is already open; if so, close it.
* Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
* Return fd2 if all went well; return BADEXIT otherwise.
#include "config.h"
#if defined(HAVE_FCNTL)
# include <fcntl.h>
#if !defined(HAVE_FCNTL) || !defined(F_DUPFD)
# include <errno.h>
#define BADEXIT -1
dup2(fd1, fd2)
int fd1, fd2;
#if defined(HAVE_FCNTL) && defined(F_DUPFD)
if (fd1 != fd2) {
#ifdef F_GETFL
if (fcntl(fd1, F_GETFL) < 0)
return BADEXIT;
if (fcntl(fd2, F_GETFL) >= 0)
if (fcntl(fd1, F_DUPFD, fd2) < 0)
return BADEXIT;
return fd2;
extern int errno;
int i, fd, fds[256];
if (fd1 == fd2) return 0;
for (i=0; i<256; i++) {
fd = fds[i] = dup(fd1);
if (fd == fd2) break;
while (i) {
if (fd == fd2) return 0;
errno = EMFILE;
return BADEXIT;
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