Opening Multiple Text Files

[emaghero]

Hello all, I want to open multiple txt files with similar names in C++
I have attempted this with the following code

//Create as many txt files as there are valid propagation constants
//Propagation constants are elements of the vector beta
        for(int j=0;j<(int)(number_of_nodes);j++){
            if(*(beta+j)>substrate*k && *(beta+i)<core*k){
                FILE *p_j;
                p_j=fopen("c:\\data_j.txt","w");
            }
        }
 

The idea is that I would open a set of txt files data_1, data_2, data_3....etc
so that I can send data to each of these txt files later.

The code as it stands doesn't work. It just opens a single txt file called data_j.txt

Can anyojne tell me how to do it so it creates multiple files with different file names?

[rajesh6695]

#include <stdio.h>
#include <conio.h>
#include <string.h>
int main()
{
  char a[10]="d:\\a1.txt";
    FILE *fp;
    int j;
    for(j=65;j<=90;j++)
    {
  a[5]=j;
 
  fp=fopen(a,"w");
  fprintf(fp,"My program");
  fclose(fp);
 
 
      j++;
    }
 
    return 0;
}

This is the one way to create no of files....

[emaghero]

#include <stdio.h>
#include <conio.h>
#include <string.h>
int main()
{
char a[10]="d:\\a1.txt ";
FILE *fp;
int j;
for(j=65;j<=90; j++)
{
a[5]=j;

fp=fopen(a,"w") ;
fprintf(fp,"My program");
fclose(fp);


j++;
}

return 0;
}

How does this work?

[Ganon11]

Hello all, I want to open multiple txt files with similar names in C++
I have attempted this with the following code

//Create as many txt files as there are valid propagation constants
//Propagation constants are elements of the vector beta
        for(int j=0;j<(int)(number_of_nodes);j++){
            if(*(beta+j)>substrate*k && *(beta+i)<core*k){
                FILE *p_j;
                p_j=fopen("c:\\data_j.txt","w");
            }
        }
 

The idea is that I would open a set of txt files data_1, data_2, data_3....etc
so that I can send data to each of these txt files later.

The code as it stands doesn't work. It just opens a single txt file called data_j.txt

Can anyojne tell me how to do it so it creates multiple files with different file names?

Instead of using j directly inside the string, you will have to create the string manually. You can add the following two statements:

char* filename = "c:\\data_X.txt";
filename[8] = j; // the X is at position 8

to your loop to create the filename - then use

p_j=fopen(filename, "w");

You may have to create the array using some different method (like malloc), but I'm not experienced with these methods.