In many instances of reading data from a file we must skip several lines of text and zoom into the lines which contain the numerical data we need.  An easy device for achieving this is the I/O stream member function .getline which is used in conjunction with a file stream. The arguments of the function .getline are a) a character array and b) the size of the array.

The following example illustrates the use of this function.

 /* An example on the use of  .getline() :
                                        file: 6ex6.cpp
   FALL 1998
   ___________________________________
   Jacob Y. Kazakia   jyk0
   October 21, 1998
   Recitation Instructor: J.Y.Kazakia
   Recitation Section  01
   ___________________________________
 
 
Purpose: This program reads from a file named 6ex6data.txt.
         It uses the function .getline to skip the first
         few  lines of the file and then reads the second
         line of the numerical data.
 
 
The file 6ex6data.txt  looks like this:

___________________________________________________________
 
 
            THE DRAG FORCE CALCULATED FOR AN OBJECT OF
               FRONTAL AREA 2 m2  USING  cd = 0.3
 
 
              Speed                     Drag Force
       m/s         miles/hour        Newtons      Pounds
 
 
         0              0              0              0
         5        11.1857         9.1875        2.06553
        10        22.3714          36.75        8.26214
        15         33.557        82.6875        18.5898
        20        44.7427            147        33.0485
        25        55.9284        229.688        51.6383
        30        67.1141         330.75        74.3592
        35        78.2998        450.188        101.211
        40        89.4855            588        132.194
 
 
  End of this table
___________________________________________________________

*/

#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
 
 
void main()
{
// declare the variables of the main function
 
 
float speedMPS;
float speedMPH;
float dragNEWTONS;
float dragPOUNDS;
 
 
char a[80]; // array used to store the data read from the first 8  
            // lines
int m;
 
 
ifstream table ( "6ex6data.txt" , ios:: in);

for ( m = 0 ; m <= 7 ; m++ )
{
table.getline( a, 80 );
}

  //  read the data desired
 
 
table >> speedMPS >> speedMPH >> dragNEWTONS >> dragPOUNDS;
 
 
//  output the data
 
 
cout << " \n speed in meters per second " << speedMPS ;
cout << " \n speed in miles per hour    " << speedMPH ;
cout << " \n drag force in Newtons      " << dragNEWTONS ;
cout << " \n drag force in pounds       " << dragPOUNDS ;
 
 
 
 
cout<<" \n\n enter e (exit) to terminate the program....";
char hold;
cin>>hold;
}