Reading and writing TXT file

[Theisar]

Hello!
Yet another question of these, and trust me, i've been trying all solutions on the page regarding this topic, but nothing works.

MY ASSIGNMENT
I have a text file (.TXT) which i have already put into the Xcode "Derived Data" folder (yup using Xcode for mac). The txt file consists of 1 column, with 8 lines.

Ie:

Headline:
word 1
word 2
.
.
.
word 8

i want to ifstream the file above, read how many lines, and PRINT all the lines. Bare in mind, the words are not on 1 line, they have each of their own line. They are of different lengths, and im not supposed to know that there are 8 lines.

Should i use vectors, arrays....

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

using namespace std;


int main ()
{
    ifstream indFil;
    indFil.open("dosmer.txt");
    string elementer,linjer;
    
    
    //kontrollerer fejl
    if (indFil.fail()) {
        cerr << "Opening file failed!" << endl;
        exit(1);
    }
    
    int count = 0;
    
    //Read how many lines there are in the file (WORKS!)
    while (!indFil.eof()) {
        indFil>>elementer;
        count++;
    }
    
    cout << count << " lines found! " << endl;
    
    
    // now print what's in these lines
    while (indFil >> linjer){
        cout << linjer << endl;
    }
    
    indFil.close();
    
   
return 0;
}

please give me some examples of how to do it. thanks in advance.

[SECMoG1T]

Use getline () instead

[Theisar]

like this: (?)

// print the elements in the file
    cout << "Following items has to be bought:" << endl;
    cout << "=========================" << endl;
    
    while (! indFil.eof()) {
        indFil.getline(&linjer, sizeof(linjer));
        cout << linjer << endl;
    }
    
    return 0;

my output still only reads the numbers of lines, that the working "while" loop in "op" shows. non of the items thats in the txt. file

[SECMoG1T]

Here is the idea

  ifstream in ("dosmer.txt");
  std::size_t  lines=0;
  std::vector<std::string> my_dosmer;
  std::string temp;

  if(! in)
   { std::cout <<" reading failed"; exit (0); }

  while(getline (in, temp, '\n'))
   {
      my_dosmer.push_back (temp);
      ++lines;
   }

   in.close ();

   std::cout <<" line count  :"<<lines <<std::endl;
   std::cout <<" content \n";

   for (const auto& str : my_dosmer)
      {
        std::cout <<str <<std::endl;
      }

  

The reason your code from line 33 dint work is because your stream was already at EOF , you could also solve your problem by closing your stream, clear the error state then reopen your file again.

[Theisar]

@andy1992 i thank you for you help, but i cant get it to work. take a look at my code so far.

initializes:

ifstream indFil;
    indFil.open("dosmer.txt");
    string elementer;
    vector<string> linjer;

then all the code that works, and then yours:

    for (const auto& str : linjer) {
        cout << str << endl;
    }
    
    return 0;
}

btw, i did the indFil.close().

[SECMoG1T]

Please post your whole code so that I can check it out.

[Theisar]

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

using namespace std;


int main ()
{
    ifstream indFil;
    indFil.open("dosmer.txt");
    string elementer;
    vector<string> linjer;
    
    
    //error check and msg
    if (indFil.fail()) {
        cerr << "Åbning af fil mislykkedes!" << endl;
        exit(1);
    }
    
    int count = 0;
    
    //Print how many lines are in text file
    while (!indFil.eof()) {
        indFil>>elementer;
        count++;
    }
    
    cout << count << " linjer fundet! " << endl;
    cout << endl;
    
    indFil.close();
    
    // print elements in file preceded by headline and ==== line
    cout << "Følgende ting skal købes:" << endl;
    cout << "=========================" << endl;
    
    for (const auto& str : linjer) {
        cout << str << endl;
    }
    
    return 0;
}

[SECMoG1T]

Well just a simple error , in your loop on line 26:-
1. You'll need to add elementer into the vector "linjer"
linjer.push_back (elementer); /// add these on line 27

2. The reason I decided to use getline is because what if one line could have a string like
"My name" this will be a logical bug , your count would register these words as different
lines

3.

print elements in file preceded by headline and ==== line

If your file contains a headline you'll need to ignore the first reading inside
The loop.

[Theisar]

like this?

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

using namespace std;


int main ()
{
    ifstream indFil;
    indFil.open("dosmer.txt");
    string elementer;
    vector<string> linjer;
    
    
    //kontrollerer fejl
    if (indFil.fail()) {
        linjer.push_back(elementer);
        cerr << "Åbning af fil mislykkedes!" << endl;
        exit(1);
    }
    
    int count = 0;
    
    //Læs hvor mange linjer der er i filen
    while (!indFil.eof()) {
        indFil>>elementer;
        count++;
    }
    
    cout << count << " linjer fundet! " << endl;
    cout << "\n";
    
    indFil.close();
    
    // print elementer i filen
    cout << "Følgende ting skal købes:" << endl;
    cout << "=========================" << endl;
    
    for (const auto& str : linjer) {
        cout << str << endl;
    }
    
    indFil.close();
    
    return 0;
}

i dont see why i should put linjer.push_back (elementer); in the error controle? O.o

just fyi. my text file looks like this:

Indkoebsseddel:
Juice
Aebler
Bananer
Maelk
Bananer
Gaer
Havregryn

[SECMoG1T]

Well line 27 shouldn't be in your error checker, should be like these:-

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

  int main () 
   {
      ifstream indFil; 
      indFil.open("dosmer.txt");

     string elementer, headline; 
     vector<string> linjer; 

    //kontrollerer fejl
    if (indFil.fail())
     {  cerr << "Åbning af fil mislykkedes!" << endl; exit(1); }

    int count = 0; 

    //Læs hvor mange linjer der er i filen 
    
    indFil>> headline; /// ignore your headline
    while (!indFil.eof()) 
     { 
       indFil>>elementer; count++;  
       linjer.push_back(elementer);
      }

      cout << count << " linjer fundet! " << endl;
      cout << "\n"; 
  
      indFil.close();

      // print elementer i filen
      cout << "Følgende ting skal købes:" << endl; 
      cout << "=========================" << endl; 

     for (const auto& str : linjer)
      { 
         cout << str << endl; 
      } 

     /* the above loop is equivalent to
      *  for (unsigned int j=0; j <linjer.size (); j++)
      *    {
      *       cout <<linjer [j]<<endl;
      *    }
      */

      return 0;
  }

Hope that works.

[Theisar]

it fuckin works!! thank YOU Andy..

[jlb]

I actually recommend a few changes:

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

using namespace std;

int main ()
{
   ifstream indFil("dosmer.txt"); // Note the open() function not needed.

   string elementer, headline;
   vector<string> linjer;

   //kontrollerer fejl
   if (indFil.fail())
   {
      cerr << "Åbning af fil mislykkedes!" << endl;
      return(1);  // Note this is main() a return is preferred over exit(). 
   }

   //Læs hvor mange linjer der er i filen

   //indFil >> headline; /// ignore your headline
   getline(indFil, headline); // Note I recommend getline(), no worry about spaces.
   
   while(indFil >> elementer)  // Note using the actual read to control the loop.
   {
      linjer.push_back(elementer);
   }
   
   // Note count no longer needed, a vector knows it's size.
   cout << linjer.size() << " linjer fundet! " << endl;
   cout << "\n";

   // indFil.close(); // Note this close is not needed, just let the destructor do it's job.

   // print elementer i filen
   cout << "Følgende ting skal købes:" << endl;
   cout << "=========================" << endl;

   for (const auto& str : linjer)
   {
      cout << str << endl;
   }

   /* the above loop is equivalent to
    *  for (unsigned int j=0; j <linjer.size (); j++)
    *    {
    *       cout <<linjer [j]<<endl;
    *    }
    */

   return 0;
}

You should strive to avoid the exit() function whenever possible in a C++ program. This C function doesn't understand C++ classes and it's use can result in data corruption.