Слияние двух текстовых файлов

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
 
 
int foo(const char * file1,const char * file2,const char * outputfile){
    FILE * f, * frez;
    char * buffer;
    int count=0;
    fpos_t pos;
    f=fopen(file1,"rb");
    frez=fopen(outputfile,"wb");    
    fseek(f,0,SEEK_END);
    fgetpos(f,&pos);
    count+=pos;
    buffer=(char*)malloc(sizeof(*buffer)*pos);
    fseek(f,0,SEEK_SET);
    fread(buffer,sizeof(*buffer),pos,f);
    fwrite(buffer,sizeof(*buffer),pos,frez);
    fclose(f);
    free(buffer);
    f=fopen(file2,"rb");
    fseek(f,0,SEEK_END);
    fgetpos(f,&pos);
    count+=pos;
    buffer=(char*)malloc(sizeof(*buffer)*pos);
    fseek(f,0,SEEK_SET);
    fread(buffer,sizeof(*buffer),pos,f);
    fwrite(buffer,sizeof(*buffer),pos,frez);
    fclose(f);
    free(buffer);
    fclose(frez);
    return count;
}
 
int main(){
    printf("Count: %d\n",foo("one.txt","two.txt","output.txt"));
    printf("Count: %d\n",foo("one.txt","output.txt","rezult.txt"));
}