刚察县公司网站建设,深圳华企立方,采集1024图片到wordpress,静态网站开发课程模板可以在管道上进行非阻塞I / O吗#xff1f; fcntl无法设置O_NONBLOCK. Linux编程接口的页面918包括一个表’从管道读取n个字节或FIFO(p)’的语义.此表列出了管道和FIFO的行为,其中一列标题为O_NONBLOCK已启用#xff1f;这意味着您可以在管道上设置O_NONBLOCK标志.它是否正确…可以在管道上进行非阻塞I / O吗 fcntl无法设置O_NONBLOCK. Linux编程接口的页面918包括一个表’从管道读取n个字节或FIFO(p)’的语义.此表列出了管道和FIFO的行为,其中一列标题为O_NONBLOCK已启用这意味着您可以在管道上设置O_NONBLOCK标志.它是否正确以下代码无法设置标志,但fcntl(2)不报告错误.#include #include #include #include #include #define SLEEP 1intmain(int argc, char *argv[]) {pid_t childPid;int pfd[2];int nread, flags;int c a;setbuf(stdout, NULL);if (pipe(pfd) -1) {printf(error: pipe);exit(EXIT_FAILURE);}switch (childPid fork()) {case -1:printf(error: fork);exit(EXIT_FAILURE);case 0: /* child */if (close(pfd[0]) -1) {printf(child: close pfd read);exit(EXIT_FAILURE);}sleep(SLEEP);_exit(EXIT_SUCCESS);default:break;/* parent falls through */}if (close(pfd[1]) -1) {printf(parent: close pipe write);exit(EXIT_FAILURE);}flags fcntl(pfd[0], F_GETFD);flags | O_NONBLOCK;if (fcntl(pfd[0], F_SETFD, flags))perror(fcntl);/* verify flags set correctly */flags fcntl(pfd[0], F_GETFD);if (!(flags O_NONBLOCK)) {printf(failed to set O_NONBLOCK\n);exit(EXIT_FAILURE);}wait(NULL);exit(EXIT_SUCCESS);}解决方法:管道和O_NONBLOCK没有什么特别之处.以下示例按预期工作.我没有检查每次调用的每个retval,以使示例更具可读性.真实世界的应用程序必须进行检查.#include #include #include #include int main(){int fds[2];pid_t pid;char buf[100];pipe(fds);pid fork();if ( pid ){while (1 ){memcpy( buf, abcdefghi\0,10);write( fds[1], buf, 10);sleep(2);}}else{int retval fcntl( fds[0], F_SETFL, fcntl(fds[0], F_GETFL) | O_NONBLOCK);printf(Ret from fcntl: %d\n, retval);while (1){ssize_t rread( fds[0], buf, 10 );printf(read: %d\n, r);if ( r 0 ){printf(Buffer: %s\n, buf);}else{printf(Read nothing\n);perror(Error was);sleep(1);}}}}写完我的例子后,我检查你的代码,发现flags fcntl(pfd[0], F_GETFD);flags | O_NONBLOCK;if (fcntl(pfd[0], F_SETFD, flags))请将F_SETFD更改为F_SETFL以及get操作.您不会更改文件描述符标志,但文件描述符状态标志:-)来自man 3 fcntlFile descriptor flagsThe following commands manipulate the flags associated with a filedescriptor. Currently, only one such flag is defined: FD_CLOEXEC, theclose-on-exec flag. If the FD_CLOEXEC bit is 0, the file descriptorwill remain open across an execve(2), otherwise it will be closed.File status flagsEach open file description has certain associated status flags, ini‐tialized by open(2) and possibly modified by fcntl(). Duplicated filedescriptors (made with dup(2), fcntl(F_DUPFD), fork(2), etc.) refer tothe same open file description, and thus share the same file statusflags.F_SETFL (int)Set the file status flags to the value specified by arg. Fileaccess mode (O_RDONLY, O_WRONLY, O_RDWR) and file creation flags(i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC) in arg are ignored.On Linux this command can change only the O_APPEND, O_ASYNC,O_DIRECT, O_NOATIME, and O_NONBLOCK flags. It is not possibleto change the O_DSYNC and O_SYNC flags; see BUGS, below.标签linux,pipe,glibc来源 https://codeday.me/bug/20190727/1555320.html
