How to extract specific data from text file containing whitespace and newlines? - c++

Question

I would like to extract and analyze data from a large text file. The data contains floats, integers and words.
The way I thought of doing this is to extract a complete line (up to newline) using std::getline(). Then extract individual data from the line extracted before (extract until whitespace, then repeat).
So far I have this:
int main( )
{
std::ifstream myfile;
myfile.open( "example.txt", std::ios::in );
if( !(myfile.is_open()) )
{ std::cout << "Error Opening File";
std::exit(0); }
std::string firstline;
while( myfile.good() )
{
std::getline( myfile, firstline);
std::cout<< "\n" << firstline <<"\n";
}
myfile.close();
return 0;
}
I have several problems:
1) How do I extract up to a whitespace?
2) What would be the best method of storing the data? There are about 7-9 data types, and the data file is large.
EDIT: An example of the file would be:
Result Time Current Path Requirements
PASS 04:31:05 14.3 Super_Duper_capacitor_413 -39.23
FAIL 04:31:45 13.2 Super_Duper_capacitor_413 -45.23
...
Ultimately I would like to analyze the data, but so far I'm more concerned about proper input/reading.

Answer 1

You can use std::stringstream to parse the data and let it worry about skipping the whitspaces. Since each element in the input line appears to require additional processing just parse them into local variables and after all post processing is done store the final results into a data structure.
#include <sstream>
#include <iomanip>
std::stringstream templine(firstline);
std::string passfail;
float floatvalue1;
std::string timestr;
std::string namestr;
float floatvalue2;
// split to two lines for readability
templine >> std::skipws; // no need to worry about whitespaces
templine >> passfail >> timestr >> floatvalue1 >> namestr >> floatvalue2;
If you do not need or want to validate that the data is in the correct format you can parse the lines directly into a data structure.
struct LineData
{
std::string passfail;
float floatvalue1;
int hour;
int minute;
int seconds;
std::string namestr;
float floatvalue2;
};
LineData a;
char sep;
// parse the pass/fail
templine >> a.passfail;
// parse time value
templine >> a.hour >> sep >> a.minute >> sep >> a.seconds;
// parse the rest of the data
templine >> a.timestr >> a.floatvalue1 >> a.namestr >> a.floatvalue2;

Answer 2

For the first question, you can do this:
while( myfile.good() )
{
std::getline( myfile, firstline);
std::cout<< "\n" << firstline <<"\n";
std::stringstream ss(firstline);
std::string word;
while (std::getline(ss,word,' '))
{
std::cout << "Word: " << word << std::endl;
}
}
As for the second question, can you give us more precision about the data types and what is it you want to do with the data once stored?