c - Printf statments not printing in order

Question

typedef struct node_s{
int data;         
struct node_s *next;
}node_t;                

void insert(node_t *pointer, int data){
     while(pointer->next != NULL){     
           pointer = pointer->next;     
     }                                 
     pointer->next = (node_t *)malloc(sizeof(node_t));
     pointer       = pointer->next;                   
     pointer->data = data;                            
     printf("Elemnet inserted
"); //2. Followed by this statment once done.                      
     pointer->next = NULL;                            
}
int main(){                        
    node_t *start, *temp;          
    start      = (node_t *)malloc(sizeof(node_t));
    temp       = start;                           
    temp->next = NULL;                            
    printf("1. Insert
");
    printf("2. Delete
");
    printf("3. Print
");
    printf("4. Find
");

    while(1){
     int input;
     scanf("%d
", &input);

     if(input==1){
        int data;
        printf("Input data
");//1. I want this to print out first once I give 1 input.
        fflush(stdout);
        scanf("%d", &data);
        insert(start, data);
     }
    }

When I compile and execute, I can give inputs but the order of printf statements are not in sequence. For instance, this is how I get the output after I give input and enter the data.

sh-4.1$ ./linked_list
1. Insert
2. Delete
3. Print
4. Find
1
23
Input data
Elemnet inserted
1
45
Input data
Elemnet inserted

I tried adding fflush(stdout), after the printf statment as well.

Answer 1

Remove from the very first scanf

scanf("%d
", &input);

What is that doing there? That is what is causing your scanf to "linger", waiting for extra input, instead of terminating immediately.

That has special meaning for scanf. When you use a whitespace character (space, tab or ) in scanf format specifier, you are explicitly asking scanf to skip all whitespace. If such character is used at the very end of scanf format string, then after reading the actual data scanf will continue to wait for input until it encounters a non-whitespace character. This is exactly what happens in your case.