Help with file Streams

This is a discussion on Help with file Streams within the C++ Programming forums, part of the General Programming Boards category; I need to make this program write to a file and read it. I have got the writing part down ...

  1. #1
    Registered User
    Join Date
    Nov 2001
    Posts
    32

    Help with file Streams

    I need to make this program write to a file and read it. I have got the writing part down but when it tries to read and display the information i get wierd numbers can anyone tell me whats wrong?

    #include <iostream.h>
    #include <fstream.h>
    #include <iomanip.h>
    #include <stdlib.h>


    int main()

    {
    int num;
    int counter=0;
    int enter;

    ofstream outstream("digits2.dat");

    if(outstream.fail())
    {
    cout<<"File Problem"<<endl;
    exit(1);
    }

    for(counter=0; counter<5; counter++)
    {
    outstream<<1;

    outstream<<2;

    outstream<<3;
    }


    outstream.close();







    ifstream instream("digits2.dat"); //opens files for reading



    if (instream.fail() )
    {
    cout<<"File problem!"<<endl;
    exit(1); //stop execution
    }



    while (instream>>num)
    {

    for(counter=0; counter<5; counter++)
    {
    cout<<num;
    }


    counter++;
    outstream<<num;
    cout<<num<<" ";
    }

    cout<<num<<endl;

    cout<<"There were "<<counter<<" numbers read"<<endl;



    instream.close();

    cout<<"\n\n Program finished";
    cin>>enter;
    return(0);

    }
    I am a C++ newb
    using: Visual C++ 6.0
    thanx for any Help

  2. #2
    Unregistered
    Guest
    ell to find a string within a line read from a file, do something like this...
    #include <stdio.h>
    #include <string.h>

    int main ( ) {
    char buff[BUFSIZ];
    FILE *fp = fopen("keywords.txt","r");
    while ( fgets( buff, BUFSIZ, fp ) != NULL ) {
    if ( strstr(buff,"word") != NULL ) {
    printf( "%s", buff );
    }
    }
    fclose( fp );
    return 0;
    }

  3. #3
    Unregistered
    Guest
    have you opened digits2.dat to see what's in it? Maybe you have a problem writing to the file, not reading from it.

    You may need to make a call to clear() after the call to fail(). I generally use the syntax: if(!outstream)

    After the first half of your program you close the ofstream. But then you use it again in the second half of the program without reopening it.

    outstream << 2; might not put anything in the file. to print 2 to the file try this outstream << "2"; or outstream << '2';

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