Return an Array in C

What is an Array?

An array is a type of data structure that stores a fixed-size of a homogeneous collection of data. In short, we can say that array is a collection of variables of the same type.

For example, if we want to declare 'n' number of variables, n1, n2...n., if we create all these variables individually, then it becomes a very tedious task. In such a case, we create an array of variables having the same type. Each element of an array can be accessed using an index of the element.

Let's first see how to pass a single-dimensional array to a function.

In the above program, we have first created the array arr[] and then we pass this array to the function getarray(). The getarray() function prints all the elements of the array arr[].

Output

Passing array to a function as a pointer

Now, we will see how to pass an array to a function as a pointer.

In the above code, we have passed the array to the function as a pointer. The function printarray() prints the elements of an array.

Output

Note: From the above examples, we observe that array is passed to a function as a reference which means that array also persist outside the function.

How to return an array from a function

Returning pointer pointing to the array

In the above program, getarray() function returns a variable 'arr'. It returns a local variable, but it is an illegal memory location to be returned, which is allocated within a function in the stack. Since the program control comes back to the main() function, and all the variables in a stack are freed. Therefore, we can say that this program is returning memory location, which is already de-allocated, so the output of the program is a segmentation fault.

Output

There are three right ways of returning an array to a function:

• Using dynamically allocated array
• Using static array
• Using structure

Returning array by passing an array which is to be returned as a parameter to the function.

Output

Returning array using malloc() function.

Output

Using Static Variable

In the above code, we have created the variable arr[] as static in getarray() function, which is available throughout the program. Therefore, the function getarray() returns the actual memory location of the variable 'arr'.

Output

Using Structure

Output