#include<stdio.h>
#include<stdlib.h>
struct node
{
    int num;
    char name[20];
    int age;
    struct node *next;
};
void main()
{
    struct node *creat();
    void print();
    struct node *head;
    head=NULL;
    head=creat(head);
    print(head);
}
/*****************************************/
struct node *creat(struct node *head)
{
    int n;
    struct node *p1=NULL,*p2=NULL;
    printf("please input a number:\n");
    scanf("%d",&n);
    for(;n>0;n--)
    {
        p1=(struct node *) malloc(sizeof(struct node));
        printf("input num,name,age\n");
        scanf("%d",p1->num);
        gets(p1->name);
        scanf("%d",p1->age);
        p1->next=NULL;
        if(head==NULL)
            head=p1;
        else
        {
            p2=p1;
            p2->next=p1;
        }
    }
    return head;
}
/*******************************************/
void print(struct node *head)
{
    struct node *temp;
    temp=head;
    while(temp!=NULL)
    {
        printf("%d, %s, %d\n",temp->num,temp->name,temp->age);
        temp=temp->next;
    }
}
谢谢

函数调用前没声明。

create函数中scanf("%d",p1->num);和scanf("%d",p1->age);的第二个参数前加取地址符&，即
scanf("%d",&p1->num);和scanf("%d",&p1->age);