Reading in different value types from file

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I want to read in a file that looks something like this:

Dom 69.5 1.80
Leigh 51.1 1.62

It must read in the first part(the name) as a string, and the next two values as floats.

Posted 4-Aug-11 0:15am

DominicZA

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వేంకటనారాయణ(venkatmakam) · Answer 1 · 2011-08-04T00:54:00

one way is to use sscanf
like,

C++

char text[] = "Dom 69.5 1.80";
sscanf(text,"%s %lf %lf",&str, &d1, &d1);

or strtok like,

C++

char stringa[] = "Dom 69.5 1.80";
    char seps[]   = " ,\t\n";

   token = strtok( stringa, seps ); 
   
   // 1st one string
   printf( " %s\n", token );
      
   //2nd double
   token = strtok( NULL, seps ); 
   double d1 = strtod(token, NULL);
   printf( " %lf", d2);
   
   //3nd double
   token = strtok( NULL, seps );
   double d2 = strtod(token, NULL);
  printf( " %lf", d1);

Orjan Westin · Answer 2 · 2011-08-05T08:24:00

The C++ way is to use streams, rather than the C library functions.

Something like this:

C++

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

// Data structure for a line from file
struct FileLine
{
  std::string name;
  float f1, f2;
};

// Reading a line from stream
FileLine ReadLine(std::istream& in)
{
  FileLine line;
  in >> line.name >> line.f1 >> line.f2;
  return line;
}

void ReadFile()
{
  // Open stream from data file
  std::ifstream in("datafile.dat");
  // Read stream
  while (!in.eof())
  {
    FileLine l = ReadLine(in);
    // do whatever
  }
}

Reading in different value types from file

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