/* * 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 #include #define BADEXIT -1 int dup2(int fd1, int fd2) { if (fd1 != fd2) { 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; } return fd2; }