How to write to a new Mac binary/executable using fopen and fwrite?

Question

I am trying to transfer files over a TCP connection, and I noticed that binary/executable files on Mac don't have file extensions. This doesn't seem to be a problem when reading from an existing binary file, but when trying to write to a new one, it creates a blank file with no extensions-nothing. How can I fix this? Here is the code:

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

int main(){
    char* filename = "helloworld";
    FILE* file = fopen(filename, "rb");
    FILE* writefile = fopen("test", "wb");
    fseek(file, 0, SEEK_END);
    unsigned int size = ftell(file);
    printf("Size of %s is: %d bytes\n", filename, size);
    fseek(file, 0, SEEK_SET);
    char* line = (char *) malloc(size+1);
    fread(line, size, 1, file);
    fwrite(line, size, 1, writefile);
    free(line);
    fclose(writefile);
    fclose(file);
    return 0;
}

helloworld is the existing executable I'm reading from (which is working) and I'm trying to write to a new executable which would be called test

Answer 1

Your code looks fine (ignoring lack of error checking). You'll need to add x (executable) permission when the copy is done.

From the terminal, you can type chmod +x test.

From within the program:

#include <sys/types.h>
#include <sys/stat.h>

...

    fclose(writefile);
    fclose(file);
    chmod("test", S_IRWXU);
    return 0;
}