Hi everyone quick c question. I have a file that is formatted in a special way. The first line is a person's first and last name, the second line is his phone number and the third is adress. this a peace of the file, it's much larger but it looks like this:

Mans Hansson

8510309159

Bössgränd 90, 373 02 RAMDALA

Olliver Lindberg

8602024898

Sandviken 76, 710 27 DYLTABRUK

Eskil Johnsson7901105838

Löberöd 29, 521 29 KÄTTLISTORP

And basically I want to read the first three lines once at a time. What I mean is I want to read line one and store in a variable called name, line 2 in phone_number and line 3 in adress and then repeat until end of file. this is my code:

int main(){
    fstream fs; 
    fs.open("/Users/brah79/Downloads/skola/c  /OOP/uppgift1/personInfo.txt"); 
    string name; 
    string phone_number; 
    string adress;
    while(!fs.eof()){
       for(int i = 0; i < 3; i  ){
        getline(fs, name); 
        getline(fs, phone_number); 
        getline(fs, adress); 
       }
       cout << "first name: " << name << endl; 
       cout << "person nummer: " << phone_number << endl; 
       cout << "adress: " << adress << endl; 
    }


    fs.close(); 



    return 0; 
}

this is the output:

first name: Eskil Johnsson

phone number: 7901105838

adress: Löberöd 29, 521 29 KÄTTLISTORP

question 1: my code is only reading the last three lines so basically information about the last person only.

question 2: the name of the person consists of first and last name and I could not figure out a way to separate them into 2 variables.

Hope my question is clear and someone can help.

CodePudding user response：

Try using fscanf(). It allows you to read formatted inputs from files. Use the value returned from the function to check if you are reading the name, the phone number or the address. If the input is always consistent (name followed by phone number followed by address) you need to change how you call fscanf().

CodePudding user response：

For a simple way to understand what's happening, lets unroll the for loop (that means we do all the statements in the loop separately).

That will give us this code:

while(!fs.eof()){
    // First iteration of the for loop
    getline(fs, name); 
    getline(fs, phone_number); 
    getline(fs, adress); 

    // Second iteration of the for loop
    getline(fs, name); 
    getline(fs, phone_number); 
    getline(fs, adress); 

    // Third iteration of the for loop
    getline(fs, name); 
    getline(fs, phone_number); 
    getline(fs, adress); 

    cout << "first name: " << name << endl; 
    cout << "person nummer: " << phone_number << endl; 
    cout << "adress: " << adress << endl; 
}

From this it will be easy to see that you discard the data you read in the first and second iteration of the for loop.

It's also possible to see that you read the whole file (assuming it's only three records) in the first iteration of the while loop.

The correct code, without the for loop and without the bad while loop condition, it should instead be something like this:

// Read three lines, until reaching EOF or an error
while(getline(fs, name) &&
      getline(fs, phone_number) &&
      getline(fs, adress))
{
    // Print the three lines we just read
    cout << "first name: " << name << endl; 
    cout << "person nummer: " << phone_number << endl; 
    cout << "adress: " << adress << endl; 
}