In Julia, to get the size of an array, you can use the built-in size() function.
Here's an example:
arr = [1, 2, 3, 4, 5]
println(size(arr)) #(5,)
The size() function returns a tuple with the dimensions of the array. In the example above, the array arr has only one dimension with a length of 5.
If you have a multi-dimensional array, the size() function will return a tuple with the length of each dimension. Here's an example:
mat = [1 2; 3 4; 5 6]
println(size(mat)) #(3, 2)
In this example, the matrix mat has two dimensions: 3 rows and 2 columns. The size() function returns a tuple with the length of each dimension, (3, 2).