reading and printing a file to screen in C
 

anyone remembers the syntax of reading a file into C and subsequently printing it out?

for eg. i have the file 'matrix.txt'
the contents inside the file is as follows:

<matrix>
rows = 2;
cols = 2;

1 2
2 4
</matrix>


how do i read it into my C program and hence prints to screen this:

1 2
2 4


the matrix should also be able to recognise that the rows and cols take the value of 2.

thanks ;)

Re: reading and printing a file to screen in C
 

#include <stdio.h>

  #include <string.h>

  

  int main(void)

  {

     int r, c, rows, cols;

     const char filename[] = "file.txt";

     FILE *file = fopen(filename, "r");

     if ( file )

     {

            if ( fscanf(file, "<matrix> rows = %d; ", &rows) == 1 &&

                     fscanf(file, "cols = %d; ", &cols) == 1 )

            {

                   for ( r = 0; r < rows; ++r )

                   {

                          for ( c = 0; c < cols; ++c )

                          {

                             double value;

                             if ( fscanf(file, "%lf", &value) != 1 )

                             {

                                    break;

                             }

                             printf("%g ", value);

                          }

                          putchar('\n');

                   }

            }

            fclose(file);

     }

     else

     {

            perror(filename);

     }

     return 0;

  }

  

  /* my output

  1 2

  2 4

  */

Re: reading and printing a file to screen in C
 

thanks so much. i understand all that have been suggested.

how about doing it in c++ syntax?
i am rather new to c++, and thus cant really convert the syntax in c to c++.

hope that someone can help me out. ;)

Re: reading and printing a file to screen in C
 

i need the codes too for readFile in
matrix.txt.. in C++

Can anyone help??

Re: reading and printing a file to screen in C
 

It would be better for you to make an attempt first, but in order to kill this in your cross-posting, here is one way.

/* file.txt

  <matrix>

  rows = 2;

  cols = 2;

  

  3 2

  4 4

  </matrix> 

  */

  

  #include <iostream>

  #include <fstream>

  #include <string>

  

  int main(void)

  {

     const std::string filename("file.txt");

     std::ifstream file(filename.c_str());

     std::string line;

     if ( getline(file, line) && line == "<matrix>" )

     {

            int rows, cols;

            if ( file >> line /* "rows" */ && 

                     file >> line /* "=" */ &&

                     file >> rows &&

                     getline(file,line) /* ; */ )

            {

                   if ( file >> line /* "cols" */ && 

                            file >> line /* "=" */ &&

                            file >> cols &&

                            getline(file,line) /* ; */ )

                   {

                          for ( int r = 0; r < rows; ++r )

                          {

                             for ( int c = 0; c < cols; ++c )

                             {

                                    double value;

                                    if ( file >> value )

                                    {

                                          std::cout << value << ' ';

                                    }

                             }

                             std::cout << std::endl;

                          }

                   }

            }

     }

     return 0;

  }

  

  /* my output

  3 2 

  4 4 

  */