Tukukkk

Hello fellow programmers.
I have little problem. I cannot figure out how to open files with different numbers (in the filename) going from 1 to whatever number of files exist.

For example, I have two (or eventually n) files named game_1.txt and game_2.txt. This loop should open these two files (or eventually all with this pattern, in that folder).

I am getting errors, namely:

passing argument 2 of 'fopen' makes pointer from integer without a
cast.

Here is what I have:

main()

{

    FILE *fr;

    int i=1;

    char b;



    while(fr=fopen("game_%d.txt",i) != NULL)

    {

        while(fscanf(fr,"%c",&b) > 0)

        {

            printf("%c",b);

        }

        i++;

    }





    return 0;

}

Use sprintf() to build the filename:

#include <stdio.h>

                // the c standard requires, that main() returns int

int main(void)  // you should put void in the parameter list if a

{               // when a function takes no parameters.

    char filename_format = "game_%d.txt";

    char filename[sizeof(filename_format) + 3];  // for up to 4 digit numbers



    for (int i = 1; i < 1000; ++i) {

        snprintf(filename, sizeof(filename), filename_format, i);

        FILE *fr = fopen(filename, "r");  // open for reading



        if(!fr)      // if the file couldn't be opened

             break;  // break the loop



        int ch;

        while ((ch = fgetc(fr)) != EOF)

            putchar(ch);



        fclose(fr);  // close the file when no longer needed.

    }                // since fr will be overwritten in the next

                     // iteration, this is our last chance.

    return 0;

}

You may need something like this:

#include <stdio.h>



int main()

{

    FILE *fr;

    int i = 1;

    char b;



    while (1) // infinite loop, until broken out of

    {

        char to_open[32];

        snprintf(to_open, 32, "game_%d.txt", i);



        if ((fr = fopen(to_open, "r")) == NULL)

        {

            break;

        }



        while (fscanf(fr, "%c", &b) > 0)

        {

            printf("%c",b);

        }



        fclose(fr); // close the file after work is done



        i++;

    }



    return 0;

}

In the original code, the API call to fopen would fail, because the second argument it requires is a string, containing the modes that should be used when opening a file (in this case I chose "r" - Open file for input operations).

The call to snprintf into an intermediate temporary array is required, because fopen does not support string formatting (such as using %d).

Afterwards, the main loop can be finished, when the next file cannot be opened anymore using the break statement.

It is also a good idea to include a call to fclose after the necessary work is done (in this case, the "work" would be the inner while loop), so that there are no unnecessary memory and resource leaks.