Thread: Reading From Files

Originally Posted by AndyBomstad

ass

Does the profanity filter catch anything at all, or just random words?

You would use ifstream in just about the opposite manner that you use ofstream. Pseudocode:

Code:

load()
{
   ifstream infile;
   infile >> all your data
}

save()
{
   ofstream outfile;
   outfile << all your data
}

Watch out, I'm about to go nuts...

Code:

#include <fstream>
#include <iostream>
#include <iterator>
#include <algorithm>
#include <list>
#include <vector>
#include <cstdlib>
#include <ctime>

int main()
{
    // Seed random number generator
    srand((unsigned)time(NULL));

    // Generate 10 random numbers, stuff into a vector container.
    std::vector<int> intVect;
    std::generate_n(std::back_inserter(intVect),10, rand);

    // Open output file and write the 10 random numbers stored in vector container to the file
    std::ofstream output("file.txt");
    std::copy(intVect.begin(),intVect.end(),
              std::ostream_iterator<int>(output," "));

    // Close the output file so we can open it below
    output.close();

    // Open an input file and create a list container
    std::ifstream input("file.txt");
    std::list<int> intList;

    // Read random ints from file into list container
    std::copy(std::istream_iterator<int>(input),std::istream_iterator<int>(),
              std::back_inserter(intList));

    // Output contents of vector to cout
    std::cout << "Vector: ";
    std::copy(intVect.begin(),intVect.end(),
              std::ostream_iterator<int>(std::cout," "));

    // Output contents of list to cout
    std::cout << "\nList  : ";
    std::copy(intList.begin(),intList.end(),
              std::ostream_iterator<int>(std::cout," "));
    std::cout << std::endl;

}

Sample output:

Code:

Vector: 1646 15613 7177 3498 1960 31613 20293 2054 15271 22660 
List  : 1646 15613 7177 3498 1960 31613 20293 2054 15271 22660

1) You want to test to make sure the file was opened properly before reading, so you can do something like this:

Code:

if(!inFile)
{
    cout<<"Failed to open file."<<endl;
    return 1;
}

2) You need to decide how much data you want to read in from the file: one character, the first word, or the whole line. If you want to read in the first word, read the data into a variable using the >> operator just like you would with cin, except substitute in your ifstream object's name:

string s;
inFile>>s;
cout<<s<<endl;



If you want to read in other amounts of data, you can use the get() or getline() functions.

string s;
getline(inFile, s); //reads in the whole line
cout<<s<<endl;


char ch;
inFile.get(ch); //reads in one character
cout<<ch<<endl;


char char_array[10];
inFile.getline(char_array, 10);
//reads in 9 chars(C++ tacks on a '\0' taking up the last spot)
//or until the end of the line
cout<<char_array<<endl;

AAAAAAAAAAAHHHHHHHHHHHHHH no one commented on him using void main()

Originally Posted by 7stud

string s;
getline(inFile, s); //reads in the whole line
cout<<s<<endl;


char ch;
inFile.get(ch); //reads in one character
cout<<ch<<endl;


char char_array[10];
inFile.getline(char_array, 10);
//reads in 9 chars(C++ tacks on a '\0' taking up the last spot)
//or until the end of the line
cout<<char_array<<endl;

ive been trying to do the same thing as well, 7stud i tryed your code and it works in part, from what i can understand the error occurs when the program encounters '\0' and by doing so it skips 1 line and goes to another.

for example. if i have an array

Code:

7
4
3
2
6
5

by using what you posted the array is displayed as

Code:

Enter filename->        array1.txt
7

3

6

any soultions? as you can see it skips every other number in the array.

Posting your code would help, but until then here is an example program that prompts the user to enter a file name and then reads the file into a vector and subsequently prints out the vector.

Code:

#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

int loadFile(vector<int>*, const char*);

int main() {

    vector<int> vFile; //create vector to hold file information
    vector<int>::iterator iFile; // create iterator to move through vector
    char fileName[10];

    cout << "Enter the name of the file: ";
    cin.getline(fileName, 10);

    if((loadFile(&vFile, fileName)) == 1) { //load our file into the vector and check for an error
        cout << "Error Loading File" << endl;
        cin.get();
        return 1;
    }


    cout << "Printing from the file:" << endl;
    
    
    for(iFile = vFile.begin(); iFile < vFile.end(); iFile++) { //move through the vector
        cout << *iFile << endl;
    }
    
    cin.get();
    return 0;
}
int loadFile(vector<int>* my_vector, const char * szfileName) {

    ifstream myFile;
    int myNumber = 0;

    myFile.open(szfileName, std::ios::in);//Load the file

    if(myFile == NULL) //check for error
        return 1;

    while(!((myFile >> myNumber)==NULL)) { //check for EOF
        my_vector->push_back(myNumber); // load contents of file into vector
    }

    myFile.close();
    return 0;
}

In my file I have:

10
20
34
23
12
34
5
85
43
10

And my output is:

Originally Posted by InvariantLoop

ive been trying to do the same thing as well, 7stud i tryed your code and it works in part, from what i can understand the error occurs when the program encounters '\0' and by doing so it skips 1 line and goes to another.

Unfortunately, I have no idea what you are talking about. The program encounters '\0'?? Where?? When??? How?? You have to be more specific. C++ is a very strongly typed and tightly structured language, and the specifics are very important, so talking in vague generalities as if you were having a conversation over a beer with a friend doesn't cut the mustard--it's all in the details.

...for example. if i have an array

Code:

7
4
3
2
6
5

An array?? Where?? An array is a C++ construct. Here is a C++ array:

char str[20];

In C++, you say str is an array. Where is your array?

...by using what you posted the array is displayed as

Code:

Enter filename->        array1.txt
7

3

6

What array??

any soultions? as you can see it skips every other number in the array.

This thread is about file input and ouput, and you are talking about arrays, so I think you might be mixed up