Delete from file max string with digit and rename outfile

#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 1024

void renameTypeFile(char src[], char dest[], char *needle, char *text){
    int c = strcspn(src, needle);
    strncpy(dest, src, c);
    strcat(dest, text);
}

int check_str(uint8_t * str){
    for (int i = 0; i < strlen((char *)str); i++) {
        if (isdigit(str[i]) > 0) {
            return 1;
        }
    }
    return 0;
}

int main(int argc, char **argv){
    if (argc < 3) {
        printf("Wrong count of params. Usage ./command [file_src_name] "
               "[file_dest_name]\n");
        exit(1);
    }

    FILE *fp, *fp2;
    if ((fp = fopen(argv[1], "r")) == NULL) {
        printf("Error open file.\n");
        exit(1);
    }

    char str2[N];
    renameTypeFile(argv[1], str2, ".", ".xyz");
    if ((fp2 = fopen(str2, "w")) == NULL) {
        printf("Error open file.\n");
        exit(1);
    }

    int max_str = atoi(argv[2]);

    uint8_t buffer[N];
    int i = 0;
    while (!feof(fp)) {
        memset(buffer, '\0', N);
        if (fgets((char *)buffer, N, fp)) {
            if (i++ >= max_str)
                break;
            if (0 == check_str(buffer)) {
                fputs((char *)buffer, fp2);
                printf("%s", buffer);
            }
        }
    }
    fclose(fp2);
    fclose(fp);
    return 0;
}