How does this implementation of randomization work in C?

问题

Since I found this particular documentation on https://www.tutorialspoint.com/c_standard_library/c_function_rand.htm,I have been thinking about this particular line of code srand((unsigned)time(&t));.Whenever I had to generate some stuff,I used srand(time(NULL)) in order not to generate the same stuff everytime I run the program,but when I came across this,I have been wondering :Is there any difference between srand((unsigned)time(&t)) and srand(time(NULL))?Because to me they seem like they do the same thing.Why is a time_t variable used?And why is the adress operator used in srand()?

#include <stdio.h>
#include<stdlib.h>
int main(){
int i,n;
time_t t;

n = 5;


srand((unsigned)time(&t)); 


for (i = 0; i < n; i++) {
    printf("%d\n", rand() % 50);
}
return(0);
}

回答1:

Yes, it will yield the same result. But the example is badly written.

I would be careful reading Tutorialspoint. It's a site known for bad C code, and many bad habits you see in questions here at SO can be traced to that site. Ok, it's anecdotal evidence, but I did ask a user here why they cast the result of malloc, and they responded that they had learned that on Tutorialspoint. You can actually see (at least) four examples in this short snippet.

They cast the result from the call to time() which is completely unnecessary and just clutters the code.
For some reason they use the variable t, which is completely useless in this example. If you read the documentation for time() you'll see that just passing NULL is perfectly adequate in this example.
Why use the variable n? For this short example it's perfectly ok with a hardcoded value. And when you use variables to avoid hardcoded values, you should declare them const and give them a much more descriptive name than n.
Omitted #include<time.h> which would be ok if they also omitted the rest of the includes.

One could also argue about two other things, but some people would disagree about these.

Why declare i outside the for loop? Declaring it inside have been legal since C99, which is 20 years old.
Why end the function with return 0? Omitting this is also ok since C99. You only need to have a return in main if you want to return something else than 0.

Both above are good to remember if your goal is to maintain very old C code in environments where you don't have compilers that supports C99. But how common is that?

So if I got to rewrite the example at tutorialspoint, i'd write it like this:

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(){
    srand(time(NULL)); 

    for (int i = 0; i < 5; i++) {
        printf("%d\n", rand() % 50);
    }
}

One thing they made good is that they used int main() instead of int main(int argc, char **argv). There's no reason to use the second signature if you're not using the variables.

来源：https://stackoverflow.com/questions/55731494/how-does-this-implementation-of-randomization-work-in-c

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srand