int mydup2(int oldfd, int newfd) { int tfd = 0; if (newfd < 0) { err_sys("newfd < 0"); } if (newfd == oldfd) { return oldfd; } while(1) { tfd = dup(ol ...
int mydup2(int oldfd, int newfd) { int tfd = 0; if (newfd < 0) { err_sys("newfd < 0"); } if (newfd == oldfd) { return oldfd; } while(1) { tfd = dup(oldfd); if (tfd == newfd) { return newfd; } else if (tfd > newfd) { close(newfd); } } } 測試： #include "apue.h" #include <fcntl.h> int mydup2(int oldfd, int newfd); int main(void) { int fd = 0; fd = open("testdup2.dat", O_RDWR | O_CREAT | O_TRUNC); if (fd < 0) { printf("open error.\n"); return -1; } if (mydup2(fd, STDOUT_FILENO) < 0) { printf("mydup2 error\n"); return -1; } printf("slk\n"); return 0; } int mydup2(int oldfd, int newfd) { int tfd = 0; if (newfd < 0) { err_sys("newfd < 0"); } if (newfd == oldfd) { return oldfd; } while(1) { tfd = dup(oldfd); if (tfd == newfd) { return newfd; } else if (tfd > newfd) { close(newfd); } } } 可以把輸出重定向到testdup2.dat，成功
