使用C中的管道传递多个数据块

Question

我需要向子进程发送3个char缓冲区，我想将它们视为3个独立的数据块。我想过使用read()和write()系统调用，但在阅读man之后我无法看到分离数据的方法 - 如果我理解正确，如果我逐个编写3个缓冲区父进程，然后一个read()的调用将读取所有数据。当然我可以在输入缓冲区中放置一些像'\0'这样的分隔符并将子数据分开，但我正在寻找一些更优雅的方法来实现这一点。那么，是否存在某种能够顺序传递数据的系统调用？

Answer 1

One possibility is to use what stdio.h already gives you: fdopen() the respective ends of the pipes and use fgets()/fputs() with the FILE pointers. This assumes your data doesn't contain newlines.

Some alternatives could be to use fixed sizes with read()/write() or to use some other delimiter and parse the received data with strtok(). You could also send the size first so the child knows how many bytes to read in the next read() call. There are really lots of options.

Answer 2

If you have it, you can use O_DIRECT to get a "packet-oriented" pipe, but there are limitations of course.

In general for a text-based streamed protocol having separators is cleaner in my opinion.

Answer 3

You have two choices

1. Put delimiters in the data (as you mentioned in the question).
2. Provide feedback from the child. In other words, after writing a chunk of data to the pipe, the parent waits for a response from the child, e.g. on a second pipe, or using a semaphore.

Answer 4

您可以在每个数据块之前添加标题，如果数据块可以是可变长度，则包括长度字段。读者可以读取标题，然后读取块内容。