Creating files/folders with system calls to mkdir in C

folders.c

// clang folders.c -o folders
// Creating folders with system calls to mkdir

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main()
{
    const int layer1 = 5;
    const int layer2 = 10;
    const int outfiles = 100;

    char buffer[100];
    int i = 0;
    for (; i < layer1; ++i)
    {
        sprintf(buffer, "mkdir folder%d", i);
        system(buffer);
        
        int j = 0;
        for (; j < layer2; ++j)
        {
            sprintf(buffer, "mkdir folder%d/xyz%d", i, j);
            system(buffer);
            int k = 0;
            for (; k < outfiles; ++k)
            {
                sprintf(buffer, "folder%d/xyz%d/fichier%d.xml", i, j, k);
                FILE *out = fopen(buffer, "w");
                fprintf(out, "<xml>\n  <i>%d</i>\n  <j>%d</j>\n  <k>%d</k>\n</xml>", i, j, k);
                fclose(out);
            }
        }
    }
    return EXIT_SUCCESS;
}