reading saved file

This is a discussion on reading saved file within the C++ Programming forums, part of the General Programming Boards category; ok i am making a game and i wont to save it. like with file inout and output so when ...

  1. #1
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    reading saved file

    ok i am making a game and i wont to save it. like with file inout and output so when the program ends it will be able to use the data.
    so what i was thinking hay lets have it make a .txt file and have it save the numbers ther.
    but how do i get is to read specific lines of the file and output only that here is a kind of example of what i wanna do:
    the file says this:
    Code:
    50
    30
    60
    hello
    ok that was me example text file now how would i get it to output from that file somehting like this:
    Code:
    30
    or
    Code:
    hello
    like that with just and output of one line.
    for the numbers i wont to be able to store and assign them.
    ps thanx in advance for however can help me.

  2. #2
    VA National Guard The Brain's Avatar
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    1) attempt to open the file. if file does not exist, handle the error.

    2) ok.. file exists. read in the entire file, loading each word into a vector of strings. (if you know for certain your file will be a fixed number of words, feel free to use a static array of strings instead of vector)

    3) your file is now in an easily accessable data structure. access your vector just like you would a normal array.




    The two most popular methods for reading from a file: use getline( ) in a loop to read in an entire line from the file at a time. -or- use (ifstreamObject >> stringObject) in a loop to read in a single word at a time from the file.


    Here is a tutorial on how to use the fstream library for file i/o. Might not be easy to follow for a beginner. Google for basic c++ file i/o if necessary.

    Here is an example program using <fstream> and <vector> constructs.. and the getline( ) function. focus on how the files are opened and loaded into the program.

    Here is a program that will read in from a file word at a time.


    Testing to see if file exists is more important for a read operation than a 'write' operation. If the file does not exist for a write operation, fstream will simply create the file, then write to the file. However, if you are trying to read from a file that does not exist, your program will come to a grinding halt unless you properly handle the error (perhaps prompting the user to re-enter the file name.. or even ask to create a new file.. or whatever, just handle the error)
    Last edited by The Brain; 07-09-2005 at 03:51 AM.
    • "Problem Solving C++, The Object of Programming" -Walter Savitch
    • "Data Structures and Other Objects using C++" -Walter Savitch
    • "Assembly Language for Intel-Based Computers" -Kip Irvine
    • "Programming Windows, 5th edition" -Charles Petzold
    • "Visual C++ MFC Programming by Example" -John E. Swanke
    • "Network Programming Windows" -Jones/Ohlund
    • "Sams Teach Yourself Game Programming in 24 Hours" -Michael Morrison
    • "Mathmatics for 3D Game Programming & Computer Graphics" -Eric Lengyel

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