https://bugzilla.kernel.org/show_bug.cgi?id=95191 Bug ID: 95191 Summary: document behavior of open(2) when path names a fifo with no readers Product: Documentation Version: unspecified Hardware: All OS: Linux Status: NEW Severity: normal Priority: P1 Component: man-pages Assignee: documentation_man-pages@xxxxxxxxxxxxxxxxxxxx Reporter: jason.vas.dias@xxxxxxxxx Regression: No linux 3.13 open() , if the path refers to a fifo, and O_WRONLY is set in its flags , but not O_NONBLOCK, then it does not return until a reader has connected to the output end of the pipe. This fact is not documented anywhere in the open(2) manual page - in fact, it only mentions : ENXIO O_NONBLOCK | O_WRONLY is set, the named file is a FIFO and no process has the file open for reading. Or, the file is a device special file and no corresponding device exists. You can easily verify this behaviour with bash : $ mkfifo /tmp/a.fifo $ strace -f bash -c 'echo 1 >/tmp/a.fifo' & ... open("/tmp/a.fifo", O_WRONLY|O_CREAT|O_TRUNC, 0666 $ read res </tmp/a.fifo ) = 3 fcntl(1, F_GETFD) = 0 fcntl(1, F_DUPFD, 10) = 10 fcntl(1, F_GETFD) = 0 fcntl(10, F_SETFD, FD_CLOEXEC) = 0 dup2(3, 1) = 1 close(3) = 0 write(1, "1\n", 2) = 2 dup2(10, 1) = 1 fcntl(10, F_GETFD) = 0x1 (flags FD_CLOEXEC) close(10) = 0 rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 exit_group(0) = ? +++ exited with 0 +++ Please add words to the effect : "If the path refers to a named pipe (FIFO), and O_NONBLOCK is not set, open() will block until a reader is connected to the write end of the pipe. " to the open(2) manual page. -- You are receiving this mail because: You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
