Pass array to function (C) - arrays

Question

I've written a function to rotate an array,
I've checked and it works when code is in one block I.E. everything
is coded under main(), but when I divide the code so that the rotation is done under a different function I can't get it to work (it truncates instead of rotating).
I'm pretty sure it's something to do with the array pointer.
sorry complete noob
please help:
#include<stdio.h>
void rotate(int *arr,int length);
int main()
{
// this code creates an array via input
int length;
int i;
int num;
printf("enter length of array\n");
scanf("%d",&length);
int arr[length];
for (i=0;i<length;i++) {
printf("enter number\n");
scanf("%d",&num);
arr[i]=num;
}
// just prints original
for(i=0;i<length;i++){
printf("original arr[%d]=%d\n",i,arr[i]);
}
//runs rotate function
rotate(arr,length);
return 0;
}
//the rotate function inputs rotation amount and uses nested for loop to
execute
void rotate(int *arr,int length)
{
int n;
printf("by how many do you want to rotate array?");
scanf("%d",&n);
int i;
int j;
int temp;
for (j=0;j<n;j++)
{
temp=arr[0];
for (i=0;i<length-1;i++)
{
arr[i]=arr[i+1];
}
arr[length-1]=temp;
printf("rotated arr[%d] = %d\n",i,arr[i]);
}
}
my output looks like this:
enter length of array
5
enter number
1
enter number
2
enter number
3
enter number
4
enter number
5
original arr[0]=1
original arr[1]=2
original arr[2]=3
original arr[3]=4
original arr[4]=5
by how many do you want to rotate array?
3
rotated arr[4] = 1
rotated arr[4] = 2
rotated arr[4] = 3
RUN FINISHED; exit value 0; real time: 9s; user: 0ms; system: 0ms

Answer 1

In C you need to declare the function before "main" function, or do the declaration and definition both above the main function. Also do share your error message, for help.
Also, in C language you can't really create dynamic arrays like that( i.e. taking an integer value and then defining the size of array using it "int array[integer] " is wrong of doing it, if the value of integer is being given during runtime)
Read http://www.mathcs.emory.edu/~cheung/Courses/255/Syllabus/2-C-adv-data/dyn-array.html , or any other tutorial about dynamic arrays in C and how to use malloc and calloc.

Answer 2

According to me the problem is in your last print statement in rotate method which is inside the loop.
you must loop through the whole array again to print the rotated array.
like this.
void rotate(int *arr,int length)
{
int n;
printf("by how many do you want to rotate array?");
scanf("%d",&n);
int i;
int j;
int temp;
for (j=0;j<n;j++)
{
temp=arr[0];
for (i=0;i<length-1;i++)
{
arr[i]=arr[i+1];
}
arr[length-1]=temp;
}
for(i=0;i<length;i++){
printf("original arr[%d]=%d\n",i,arr[i]);
}
}
this will work.
And also, Always define functions at the top in c.