ERROR: segmentation fault (core dumped)

[sunny543]

when i am trying to run this program on ubuntu it compiles but when i run it it flags as "segmentation fault (core dumped)". can anyone tell me how to get the output.the code is as follows:

#include<stdio.h>
#include<stdlib.h>


struct node{
int info;
struct node*link;
};
void append(struct node**, int);
void displ(struct node*);




void append(struct node **q, int n){
 struct node *temp,*r;


if(*q==NULL){
printf("the list has zero elements and the first node being added is %d\n",n);
temp->info=n;
temp->link=NULL;
*q=temp;
 }
else
{temp=*q;
  while(temp->link!=NULL)
      temp=temp->link;


r=malloc(sizeof(struct node));
r->info=n;
r->link=NULL;
temp->link=r;
}


}


void displ(struct node *q){
struct node *p;
for(p=q;p->link!=NULL;p=p->link)
 printf("%d",p->info);


}


 main(){
struct node *p;
int n;
p=NULL;
printf("enter value to append a node\n");
scanf("%d",&n);
//append(&p,12);
displ(p);
}

[laserlight]

For starters, you need to format your code better, especially the indentation:

#include<stdio.h>
#include<stdlib.h>

struct node {
    int info;
    struct node *link;
};

void append(struct node**, int);
void displ(struct node*);

void append(struct node **q, int n) {
    struct node *temp, *r;

    if (*q == NULL) {
        printf("the list has zero elements and the first node being added is %d\n", n);
        temp->info = n;
        temp->link = NULL;
        *q = temp;
    }
    else {
        temp = *q;
        while (temp->link != NULL)
            temp = temp->link;
        r = malloc(sizeof(struct node));
        r->info = n;
        r->link = NULL;
        temp->link = r;
    }
}

void displ(struct node *q) {
    struct node *p;
    for (p = q; p->link != NULL; p = p->link)
        printf("%d", p->info);
}

main() {
    struct node *p;
    int n;
    p = NULL;
    printf("enter value to append a node\n");
    scanf("%d", &n);
    //append(&p,12);
    displ(p);
}

Next, one problem you have is that when inserting the first node, you forgot to allocate memory for it.

[ZuK]

You're passing NULL for q

void displ(struct node *q){
    struct node *p;
    for(p=q;p->link!=NULL;p=p->link) // <<== boom
         printf("%d",p->info); // <<= boom
}

Running the program in the debugger helps a lot to find this kind of errors.
Kurt