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Unix kernel represents open files using three data structures: Descriptor table , File table , and v-node table . When a process opens a file twice, it gets two different descriptors in the descriptor table , two entries in the file table (so that they have different positions in the same file), and they both point to one entry in the v-node table . And child process inherits parent process's descriptor table , so kernel maintains one descriptor table for each process respectively. But two descriptor from different processes point to the same entry in open file table . So When child process does some read on the file, would the offset of the same file change in parent process? If 1 is true, for two processes, is there a convenient way that I can get the same effect of fork on same file? That means two processes share a position(offset) information on the same file. Is there a way to fork so that both processes have totally unrelated tables, like two unrelated processes only that they opened same files.

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