Can multiple processes open a named pipe?

Question

I'm creating a process that is going to publish data via a named pipe and I envision there being multiple subscribers. Is there some way my process can Tee off the named pipe it is wring too each time a new subscriber attempts to open the pipe?

Edit for Clarity I am trying use a broadcast model.

• I'll make no distinction if there are 1 or N subscribers.
• I do care if there are no subscribers. If no one is listening I'll turn part of the system off.
• I don't care about addressing the data. As soon as someone subscribes I want them to get the complete set of data.
• Subscribers shouldn't get any old data. As soon as they open the pipe they should be seeing new data like a stream.

Answer 1

First, the question in title:

Can multiple processes open a named pipe?

The answer is yes. I mean, more than one reader and more than one writer simultaneously.

Now your actual question:

Is there some way my process can Tee off the named pipe it is writing too each time a new subscriber attempts to open the pipe?

I'm not sure what you mean by "tee off" but here is a general answer:

• Because opening the pipe for writing is a blocking operation, until someone else opens it for reading, and because writing to a pipe with no reader triggers a SIGPIPE, your writer (the publisher) can know for sure that there is at least one reader (subscriber).
  On the other hand, the writer cannot know whether there are multiple readers at a given time (you can mitigate this by spying the fifo activity with inotify, though)
• The messages the publisher will send cannot be aimed at a specific reader.
• The content of the message that the publisher writes won't be duplicated among readers (i.e. each reader gets the same message the writer sent). Instead, each reader will read a part of it. For example, if you write "HELLO WORLD" into a pipe with three subscribers (readers), then the first one may receive "HELL", the second one "LORD" and the last one "O W"

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[edit] Now that you have clarified your question, what I have written above still applies and we can come to a conclusion: named pipes are clearly not the right tool for your needs. You probably need broadcast/multicast UDP sockets, or a dedicated messaging system like D-Bus, AMQP brokers, etc.