Step by Step solution about How to resolve the algorithm Read a file line by line step by step in the C++ programming language

Source 1:

This C++ program reads lines from a file and prints the line numbers and the lines:

• It includes the fstream and iostream standard C++ libraries.
• In the main function:
  • It declares an integer linecount to keep track of line numbers and a string line to store each line.
  • It opens an input file stream named infile using the first argument passed to the program (assuming it's the file path).
  • It checks if the file was successfully opened.
  • If the file is open, it enters a loop that continues until there are no more lines to read:
    • The program reads a line from the file into the line string using getline.
    • It prints the line number, followed by a colon, followed by the line itself.
    • It increments the linecount.
  • It closes the input file stream.
  • It returns 0 to indicate successful execution.

Source 2:

This C++ program reads comma-separated values from a file and extracts integers into variables:

• It includes the fstream, iostream, sstream, and string standard C++ libraries.
• In the main function:
  • It opens an input file stream named "thefile.txt" using the ifstream class.
  • It declares a string line to store each line.
  • It enters a loop that continues until there are no more lines to read:
    • The program reads a line from the file into the line string using getline.
    • It creates an istringstream object named iss that reads from the line string.
    • It attempts to extract two integers, a and b, from the istringstream using the >> operator.
    • If it successfully reads the integers, it prints their values.
    • If it fails to read the integers, it breaks out of the loop.
  • It prints a "finished" message to indicate that the file has been processed.

Source 3:

This U++ (Ultimate++ Library) program reads lines from a file and prints them:

• It includes the Core/Core.h header from the U++ Library.
• Using the CONSOLE_APP_MAIN macro, it defines the main function as the entry point of the console application.
• In the main function:
  • It opens an input file named from the first argument passed to the program (assuming it's the file path) using the FileIn class.
  • It enters a loop that continues until there are no more lines to read:
    • The program reads a line from the file into a string using the GetLine method of the FileIn object.
    • It prints the line to the console using the Cout object.

#include <fstream>
#include <string>
#include <iostream>

int main( int argc , char** argv ) {
   int linecount = 0 ;
   std::string line  ;
   std::ifstream infile( argv[ 1 ] ) ; // input file stream 
   if ( infile ) {
      while ( getline( infile , line ) ) {
	 std::cout << linecount << ": " 
                   << line      << '\n' ;  //supposing '\n' to be line end
	 linecount++ ;
      }
   }
   infile.close( ) ;
   return 0 ;
}


#include <fstream>
#include <iostream>
#include <sstream>
#include <string>

int main()
{
  std::ifstream infile("thefile.txt");
  std::string line;
  while (std::getline(infile, line) )
     {
        std::istringstream iss(line);
        int a, b;
        if (!(iss >> a >> b)) { break; } // if no error a and b get values from file

        std::cout << "a:\t" << a <<"\n"; 
        std::cout << "b:\t" << b <<"\n"; 
     }
      std::cout << "finished" << std::endl;
}


#include <Core/Core.h>

using namespace Upp;

CONSOLE_APP_MAIN
{
	FileIn in(CommandLine()[0]);
	while(in && !in.IsEof())
		Cout().PutLine(in.GetLine());
}