How do I get the length of an array in C?

Question

How can I get the length of an array in C, I tried it how i get it in other languages but it doesn't work like this:

int array [5];

for(int i = 0; i < array.length; i++) {..

score 5 · Answer 1 · answered Mar 11 '15 at 16:00

If its on the stack, you can use the sizeof operator to determine its raw byte size:

int array[5];
size_t array_size = sizeof(array);

But this gives you the size in bytes, not the number of elements. However, you can calculate the number of elements with this approach:

int array[5];
size_t array_elems = sizeof(array) / sizeof(* array);

If you array is a pointer (e.g. function call or dynamic memory allocation) then you have to keep track it yourself!

score 0 · Answer 2 · edited Mar 12 '15 at 20:59

0

size_t length = sizeof(array) / sizeof(array[0]);

edited Mar 12 '15 at 20:59

Marco

answered Mar 11 '15 at 15:59

lychee

downvote for correct solution? – lychee Mar 11 '15 at 19:01
1

Not my downvote. This answer is the same as that from @d3l but without any explanation. A good answer should explain why it is an answer. A short piece of code may be correct but it does not educate the asker. – AdrianHHH Mar 11 '15 at 21:47
but `size_t` is typedef as `unsigned long int` – lychee Mar 12 '15 at 20:10
Maybe, but so can it be typedef'd as `unsigned int` ;) Its implementation defined. – Marco Mar 12 '15 at 22:42
Not my downvote, but a copy-pasted code snippet is _not_ enough. – peterh Mar 13 '15 at 00:28

2 Answers2