How can I know the postion of reading in fstream

This is a discussion on How can I know the postion of reading in fstream within the C++ Programming forums, part of the General Programming Boards category; Please , If I have a read_file object of fstream, and I want to read the postion that I am ...

  1. #1
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    How can I know the postion of reading in fstream

    Please , If I have a read_file object of fstream, and I want to read the postion that I am standing on without reading it . do I ise peek() ? I tried to use it , the first read returned 91 and the next returned 81 .

    Code:
    #include <iostream.h>
    #include <fstream.h>
    
    int main(){
       int x=0;
       ifstream bin_file("c:\\compiler_test\\bin.txt");
       x = bin_file.peek();
       cout << "the first read = " << x << endl;
      bin_file.get();
      x = bin_file.peek();
      cout << "the second read = " << x;
    
      return 0;
    
    }
    thank you.

  2. #2
    Cat without Hat CornedBee's Avatar
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    "read the position without reading it"? You mean changing.

    http://msdn2.microsoft.com/en-us/lib...17(VS.80).aspx
    peek reads a character without advancing the read position. But the bin_file.get() that you have between the two peeks does.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  3. #3
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    yes, exactly !

    but how can I advance the postion ?

  4. #4
    Cat without Hat CornedBee's Avatar
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    Well, get(), getline(), read(), they all advance the position. ignore() does it without returning the data. seek() (or seekg() and seekp(), to move read and write position separately for those streams that support it) can be used too; it's especially good for large jumps.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  5. #5
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    good , but if I want to return the read postion back one char ?
    Last edited by GSalah; 11-09-2006 at 06:43 AM.

  6. #6
    Cat without Hat CornedBee's Avatar
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    tell() to save the current position, seek() to restore it. Don't you have a reference to look this stuff up?
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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