Is there any way to get the length of an array after you declare it in C?

Question

For example a code like:

int arr[5] = {1, 2, 3, 4, 5}

Is there anyway to get the 5 in arr[5]? I haven't learnt C++ before.

Have you tried `sizeof`? For an array that is an `int*`, I know that you can't. — donjuedo, Feb 25 '20 at 22:51
Make up your mind. You have a C tag on the question and you reference C++ in your post. — jwdonahue, Feb 25 '20 at 22:56
@donjuedo : _"an array that is an `int*`"_ is an oxymoron - a pointer is not an array. here `sizeof(arr) / sizeof(*arr) == 5`. — Clifford, Feb 25 '20 at 22:56
@Clifford, I am pretty sure you have a solid of C and how it handles types. There's no need for me to split hairs about `array`. — donjuedo, Feb 25 '20 at 23:00
I said that I haven't learned C++ before just in case people assumed I had learnt it. — cinos, Feb 25 '20 at 23:23
@cinos : That is understood, but your question is tagged [C], so mentioning C++ is not relevant. Presumably you are equally inproficient in C? — Clifford, Feb 26 '20 at 07:47
@donjuedo It is not splitting hairs. It is an important distinction, ant in the context of this question Irellavant. Your comment is likely to do more to confuse than to help. — Clifford, Feb 26 '20 at 07:50

Alberto Sinigaglia · Accepted Answer · 2020-02-25T22:55:57.950

4

You can get it by getting the array size and divide it by the size of a single element:

int arr[5] = {1, 2, 3, 4, 5};
size_t lengthOfArr = sizeof(arr)/sizeof(arr[0]) ;

edited Feb 25 '20 at 22:55

answered Feb 25 '20 at 22:50

"element" is more correct than "cell", if I'm not mistaken. Otherwise, great answer. – donjuedo Feb 25 '20 at 22:52
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`sizeof arr/sizeof arr[0]` is [DRY](https://en.wikipedia.org/wiki/Don%27t_repeat_yourself#DRY_vs_WET_solutions)er. – chux - Reinstate Monica Feb 25 '20 at 22:53
idk @donjuedo, english is not my native language, so if instead it's your case, i'm absolutely trust it ahah – Alberto Sinigaglia Feb 25 '20 at 22:54
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@chux-ReinstateMonica -- `sizeof arr / sizeof *arr` may be DRYer yet.... – ad absurdum Feb 25 '20 at 22:55
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C spec uses "element": e.g. "Array types are characterized by their element type and by the number of elements in the array." – chux - Reinstate Monica Feb 25 '20 at 22:55
@Berto99, Your English is excellent -- I would not have guessed it's not your first. – donjuedo Feb 25 '20 at 22:56
oh already done, thanks for the advice @donjuedo – Alberto Sinigaglia Feb 25 '20 at 22:57
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A better answer would explain that `sizeof arr` returns the number of bytes in the array. – jwdonahue Feb 25 '20 at 22:57
Thank you very much! – cinos Feb 25 '20 at 23:24

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