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 <errno.h> 15#include <fcntl.h> 16#include <unistd.h> 17 18#define BADEXIT -1 19 20int 21dup2(int fd1, int fd2) 22{ 23 if (fd1 != fd2) { 24#ifdef F_DUPFD 25 if (fcntl(fd1, F_GETFL) < 0) 26 return BADEXIT; 27 if (fcntl(fd2, F_GETFL) >= 0) 28 close(fd2); 29 if (fcntl(fd1, F_DUPFD, fd2) < 0) 30 return BADEXIT; 31#else 32 errno = ENOTSUP; 33 return BADEXIT; 34#endif 35 } 36 return fd2; 37} 38