Reading

      char buf[20];
      int br = read(3, buf, 20);

• Then the kernel does something real interesting to figure out which disk block to read

• It reads the block

• It extracts the right number of bytes ( number_read ) from the block

• It sticks the bytes into buf

• It advances the offset in the file pointer by number_read

• It arranges that number_read will be returned into br

• Writing is exactly the same, only backwards

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Copyright © 2007 M. J. Dominus