fork() call in c

I have used fork() to create 2 different processes operating开发者_开发百科 on 2 different address spaces. Now, in parent process I need the value of a variable from child's address space or if the child process can modify the variable in parent's address space. Is this possible?

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No, once you've forked, each process gets its own address space and you'll have to look into either:

• some form of IPC between the processes to access each others data (such as shared memory or message queues).
• some more lighweight variant of fork that allows sharing of data (including possibly threading).

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Once you have two processes, sharing data needs interprocess communication: file, pipe or shared memory.

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If you mean exchanging data between these two processes you can not. You can do it by system APIs like SharedMemory, Message Passing, Pipeline, Socket, ...

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As you have created two process using fork command Both Process will be in different address space so they will only communicate by IPC, message passing ,Piping , Shared Memory etc. otherwise one process can't access other process data as thay do have Process specific data and similarly threads also have thread specific data