fork and pipe

I need to use fork and pipe to read a text file. This is an assignment for a class.

Basically, I need to make 4 subprocesses to each read a portion of the input file, do some processing and return a result to the parent process so it can aggregate the children's results.

From what I understand, I should use fork to create the children, then pipe to tell each child which part of the file to do.

My question is, how do I use pipe. How do I know which child process I am talking to?

Quote:

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Originally Posted by tbarsness

My question is, how do I use pipe. How do I know which child process I am talking to?

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You create a pipe by calling pipe(). You do this before you fork(). You know which process you are talking to, because each process has its own pipe.

Thanks, I will try fork() before pipe()

Quote:

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Originally Posted by tbarsness

Thanks, I will try fork() before pipe()

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No no, pipe() before fork(). After the fork() it is too late.

And you actually need two pipes per process. Pipes are one-way, but you need two-way communication. So each process needs two pipes, one for reading, one for writing.