File I/O

File I/O Notes

File I/O

Include fstream
Need to declare variables to be "links" to files on disk
type ifstream is for an input file (instead of keyboard the input is taken from a file on disk.
type ofstream is for an output file (instead of the screen, the output is placed in a file on disk.
To declare an input file:
ifstream inputfilename
Also need to open the file for input (or output)
inputfilename.open("path/filename.ext");
You can then use the overloaded >> symbol for input
Instead of the reserved word cin, use inputfilename Sample Open and close
You need to have a file created in the given path
If no path is specified, then the input file should be in the same directory as your cpp code.

Searching for the end of the file

You can use a sentinel controlled loop to look for the last input value
Fail example
Or you can use a built-in function eof (end of file) to detect the end of the file
Fail and eof example
Appending to a file is also possible with a modfied open command:
ofstream MyOutputFile;
MyOutputFile.open ("outfile.txt", ios::app);

Getline vs. cin

#include <iostream>
#include <string>
using namespace std;

int main()
{
   string name;
   int i;

   for (i=1; i <=3; i++)
   {
       cout <<"Enter a string => ";
       cin >> name;
       cout << endl << name << endl;
   }
   return 0;
}

Enter a string => stringone	tabstringtwo

stringone
Enter a string => 
tabstringtwo
Enter a string =>    spacespacespace

spacespacespace

#include <iostream>
#include <string>
using namespace std;

int main()
{
   string name;
   int i;

   for (i=1; i <=3; i++)
   {
       cout <<"Enter a string => ";
       getline(cin, name);
       cout << endl << name << endl;
   }
   return 0;
}

Enter a string => this is a string of words

this is a string of words
Enter a string => oneword	tab	tab

oneword	tab	tab
Enter a string => x

x

#include <iostream>
#include <string>
using namespace std;

int main()
{
   string w1, w2;
   int i, num;

   
   for (i=1; i <=3; i++)
   {
       cout <<"Getline a word => ";
       getline(cin, w1);
       cout << endl << w1 << endl;
       cout <<"cin a word => ";
       cin >> w2;
       cout << endl << w2 << endl;
   }
   return 0;
}

Getline a word => wordOne wordTwo

wordOne wordTwo
cin a word => wordOne wordTwo

wordOne
Getline a word => 
 wordTwo
cin a word => wordOne

wordOne
Getline a word => 

cin a word => OOPS

OOPS