/Python/dup2.c

 1/*
 2 * Public domain dup2() lookalike
 3 * by Curtis Jackson @ AT&T Technologies, Burlington, NC
 4 * electronic address:  burl!rcj
 5 *
 6 * dup2 performs the following functions:
 7 *
 8 * Check to make sure that fd1 is a valid open file descriptor.
 9 * Check to see if fd2 is already open; if so, close it.
10 * Duplicate fd1 onto fd2; checking to make sure fd2 is a valid fd.
11 * Return fd2 if all went well; return BADEXIT otherwise.
12 */
13
14#include <fcntl.h>
15
16#define BADEXIT -1
17
18int
19dup2(int fd1, int fd2)
20{
21	if (fd1 != fd2) {
22		if (fcntl(fd1, F_GETFL) < 0)
23			return BADEXIT;
24		if (fcntl(fd2, F_GETFL) >= 0)
25			close(fd2);
26		if (fcntl(fd1, F_DUPFD, fd2) < 0)
27			return BADEXIT;
28	}
29	return fd2;
30}