Generating a random 32 bit hexadecimal value in C

Question

What would be the best way to generate a random 32-bit hexadecimal value in C? In my current implementation I am generating each bit separately but the output is not completely random ... many values are repeated several times. Is it better to generate the entire random number instead of generating each bit separately?

The random number should make use of the entire 32 bit address space (0x00000000 to 0xffffffff)

file = fopen(tracefile,"wb"); // create file
for(numberofAddress = 0; numberofAddress<10000; numberofAddress++){ //create 10000 address
    if(numberofAddress!=0)
        fprintf(file,"\n"); //start a new line, but not on the first one

    fprintf(file, "0 ");
    int space;

    for(space = 0; space<8; space++){ //remove any 0 from the left
        hexa_address = rand() % 16;
        if(hexa_address != 0){
            fprintf(file,"%x", hexa_address);
            space++;
            break;
        }
        else if(hexa_address == 0 && space == 7){ //in condition of 00000000
            fprintf(file,"%x", "0");
            space++;
        }
    }

    for(space; space<8; space++){ //continue generating the remaining address
        hexa_address = rand() % 16;
        fprintf(file,"%x", hexa_address);
    }

}

Answer 1

x = rand() & 0xff;
x |= (rand() & 0xff) << 8;
x |= (rand() & 0xff) << 16;
x |= (rand() & 0xff) << 24;

return x;

rand() doesn't return a full random 32-bit integer. Last time I checked it returned between 0 and 2^15. (I think it's implementation dependent.) So you'll have to call it multiple times and mask it.