Read in file with tabs and spaces - c++

Question

I have a text file in this format:
Petroleum Engineering 94600 175500
Marine Engineering 73900 123200
Economics and Mathematics 60000 122900
Geophysics 54100 122200
Cognitive Science 54000 121900
What I have is course name, average early career pay, and mid career pay, all separated by tabs. The course names with multiple words are separated by spaces.
I want to read the course name and put it in one variable, the first pay in a second variable, and the third pay in a third variable.
int main(){
ifstream in;
in.open("Salaries.txt");
string course;
int mid;
int avg;
if (in.fail()){
cout<< "failed to open file";
exit(1);
}
while(!in.eof()){
in >> course >> avg >> mid;
cout << course<<endl;
}
in.close();
}
When I compile this code, it outputs nothing, and the program does not exit or terminate.
Someone in comments pointed out that using eof() is not recommended, so I tried thus instead:
while(in >> course >> sm >> lg){
cout << course << endl;
}
The process exits without outputting anything to the screen. I tried it on a input file that looks something like this:
NCORES 1
NEW 0
CORE 100
INPUT 5000
CORE 20
And it takes the string and puts it into one variable, and takes the number and puts it into another variable, and prints the correct output. So the problem is the white space between the words in the cours name in the original file, and I don't know how to account for that.

Answer 1

Although your code does have other problems, the problem you're running into is from the fact that operator>> for a string stops reading at the first white space it encounters. That means on the first line, it reads Petroleum into course, then tries to read Engineering into avg. Since avg is a number, that doesn't work, so the conversion fails. From there, all further attempts at reading from the stream fail.
To fix that, you probably want to use std::getline to read the course name. It allows you to specify the character that will end the string it reads. In this case, you apparently want to pass a tab character ('\t') for that parameter.
If I were doing it, I'd probably put the three items into a struct, and overload operator>> for that struct:
struct course {
std::string name;
long early_pay;
long mid_pay;
friend std::istream &operator>>(std::istream &is, course &c) {
if (std::getline(is, c.name, '\t')) {
std::string temp;
std::getline(is, temp, '\t');
c.early_pay = std::stol(temp);
std::getline(is, temp);
c.mid_pay = std::stol(temp);
}
return is;
}
};
Then reading the data and printing out the course names would look something like this:
int main() {
std::istringstream input(
R"(Petroleum Engineering 94600 175500
Marine Engineering 73900 123200
Economics and Mathematics 60000 122900
Geophysics 54100 122200
Cognitive Science 54000 121900 )");
course c;
while (input >> c)
std::cout << c.name << '\n';
}

Answer 2

Use std::getline() to read lines from the file, and use std::istringstream to parse each line. You can then use std::getline() to read tab-delimited strings from each line. For example:
int main() {
ifstream in("Salaries.txt");
if (!in.is_open()) {
cout<< "failed to open file";
exit(1);
}
string line course;
int mid, avg;
while (getline(in, line)) {
istringstream iss(line);
getline(iss, course, '\t');
iss >> avg >> mid;
cout << course << endl;
}
return 0;
}