Fileio

#include <iostream>
#include <fstream>
using namespace std;
// dumps file to screen

int main()

{
    string line,word;
    ifstream f("mydata.txt");

    //ifstream f;
    //f.open("mydata.txt", ios::in);

    cout<<"----------reading by line -----------------------"<<endl;
    //ex #1
    while ( getline(f,line) ) //line delimeted
    {
        cout<<line<<endl;
    }

    //f.close();
    //f.open("mydata.txt", ios::in);

    f.clear(); // clear eof state flag from true to false
    //f.seekg(0); // set seek get file pointer to beginning of file

    //f.seekg(0,ios::beg);
    f.seekg(0,f.beg); //resets file pointer back to the top
    cout<<"----------reading by words-----------------------"<<endl;
    //ex #2
    while ( f >> word ) //space delimited
    {
        cout<<word<<endl;
    }

    f.clear();
    f.seekg(0,ios::beg); //set seek get file pointer with offset, so 0 offset from beginning of file
    cout<<"-----------reading by line but using eof() or good()----------------------"<<endl;
    //ex #3
    //while ( !f.eof() )
    while ( f.good() )
    {
        getline(f,line); //use with !f.eof()
        cout<<line<<endl;
    }
    cout<<"-----------reading by character-----------------------"<<endl;
    f.clear();
    f.seekg(0,ios::beg); //set seek get file pointer with offset, so 0 offset from beginning of file
    //ex #4
    char c;

    while ( f.get(c) )
    {
        cout<<c;
    }

    f.close();
    return 0;
}

#include <iostream>
#include <fstream> // ofstream ifstream
#include <vector>
#include <algorithm> //sort
using namespace std;
//reads mydata.txt into a vector. Sorts the vector alphabetically then
//writes sorted vector to newdata.txt
int main()
{
    string line;
    vector <string> list;

    //ifstream("mydata.txt");

    ifstream inf;
    inf.open("mydata.txt", ios::in); //reading

    while ( getline(inf,line) )
    {
        list.push_back(line);
    }
    inf.close();

    sort(list.begin(),list.end());

    ofstream outf;
    outf.open("newdata.txt", ios::out); //writing- warning this overwrites
    for (unsigned int x=0; x<list.size(); x++)
    {
        outf << list[x] << endl;
    }
    outf.close();
    return 0;
}

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
//sort mydata people by age

bool mycomp(pair <string, int> x, pair <string, int> y){
    return (x.second < y.second);
}

int main()

{
    string name;
    pair <string, int> p;
    int age;
    //use C++ pair      
    vector < pair<string, int> >  pv;
    ifstream inf;
    inf.open("mydata.txt", ios::in);
    while ( inf >> name && inf >> age) //extraction operator >> (space or newline delimeted)
    {
        p.first=name;
        p.second=age;
        pv.push_back(p);
    }
    inf.close();
    sort(pv.begin(),pv.end(), mycomp);
    ofstream outf;
    outf.open("newdata.txt", ios::out);
    for (unsigned int x=0; x<pv.size(); x++)
    {
        outf << pv[x].first << " " << pv[x].second << "\n";
        //cout << pv[x].first << " " << pv[x].second << "\n";
    }
    outf.close();
    return 0;
}