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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 <errno.h> // errno
#include <fcntl.h> // fcntl()
#include <unistd.h> // close()
#define BADEXIT -1
int
dup2(int fd1, int fd2)
{
if (fd1 != fd2) {
#ifdef F_DUPFD
if (fcntl(fd1, F_GETFL) < 0)
return BADEXIT;
if (fcntl(fd2, F_GETFL) >= 0)
close(fd2);
if (fcntl(fd1, F_DUPFD, fd2) < 0)
return BADEXIT;
#else
errno = ENOTSUP;
return BADEXIT;
#endif
}
return fd2;
}
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