How to separate data from getline each time there is a space-CodePudding

int main() {
    ifstream billFile;
    billFile.open("bill.in"); //opening file

    if( billFile.is_open() ){
      string line1;
      
      getline(billFile, line1);

      cout << line1 << endl;
}

The bill.in file contains:

12 100

How can I separate 12 and 100 into two different variables?

CodePudding user response：

You can use std::istringstream to parse line1:

int main()
{
    ifstream billFile("bill.in"); //opening file
    if( billFile.is_open() )
    {
        string line1;
        if( getline(billFile, line1) )
        {
            istringstream iss(line1);
            int value1, value2;
            if( iss >> value1 >> value2 )
                cout << value1 << ' ' << value2 << endl;
        }
    }
}

Of course, if your file has only 1 line, then you can just omit getline(), eg:

int main()
{
    ifstream billFile("bill.in"); //opening file
    if( billFile.is_open() )
    {
        int value1, value2;
        if( billFile >> value1 >> value2 )
            cout << value1 << ' ' << value2 << endl;
    }
}

CodePudding user response：

I use the following split function to divvy up each line based on some set of delimiters (a space in your case).

std::vector<std::string> split(const std::string& str, 
                               std::string delims = " \t") {
    std::vector<std::string> strings;
    size_t start;
    size_t end = 0;
    while ((start = str.find_first_not_of(delims, end)) != std::string::npos) {
        end = str.find_first_of(delims, start);
        strings.push_back(str.substr(start, end - start));
    }
    return strings;
}

then you can split each line into a vector of strings:

int main() {
    ifstream billFile;
    billFile.open("bill.in"); //opening file
    if( billFile.is_open() ){
      string line;
      getline(billFile, line);
      std::vector<std::string> str = split(line, " ");
      std::string line1 = str[0];
      cout << line1 << endl;
   }
}

You use this method to split up strings using any delimiter you want.

CodePudding user response：

If you input file only contains one line and your keyboard is in very poor working order and you really need to minimize keystrokes you can write:

int main(){
    int v1, v2;
    if(std::ifstream("bill.in") >> v1 >> v2){
        // here you have valid v1 and v2.
    }
}

The >> "formatted input" is appropriate here because it is convenient to understand the contents of the text file as numbers.

CodePudding user response：

Function std::getline() takes delimitation as claimed in C reference. So just use getline(istream, str, ' ');.

Modify your codes as

int main() {
ifstream billFile;
billFile.open("bill.in"); //opening file

if( billFile.is_open() ){
  string line1;
  
  getline(billFile, line1, ' ');

  cout << line1 << endl;
}