Time function syntax

Question

Why is the time function commonly used as follows:

 time_t currentTime; currentTime = time( NULL ); 

instead of this:

 time_t currentTime; time( &currentTime ); 

Is the first method used more simply because it is perhaps more readable? Or is there another reason?

Thanks.

Edit: Also, why is the time function even designed this way? Why are there two ways to set a variable?

Answer 1

It seems that it makes sense to return a value from the function than to pass the changed parameter.

Perhaps this is due to the fact that we studied in languages ​​where functions and routines were different, today I do not know about these young people.

Answer 2

Of course, only K & R probably knows the true answer, but my suspect is just an “incident” due to historical reasons for implementation. For example, the design of this function may be launched as void time(time_t*) , because it is simply impossible in some form of pre-ansi C to return a value of type time_t and only later develop into a function that returns a value.

If this is an explanation, then the reason for saving the parameter in any case is, of course, backward compatibility with existing code.

Answer 3

The most common format is time_t currentTime = time( NULL );

This is shorter and does not leave the currentTime variable uninitialized. This parameter is a historical event and does not make sense.

Answer 4

The timer parameter is a pointer to an object of type time_t, where the time value is stored. Alternatively, this parameter may be a null pointer, in which case the parameter is not used, but the time_t function is still returned by the function.

Therefore, you do not need to create a time_t object.