"search" linked list in c - c

Question

I added a "search" function for my linked list menu and I don't know what is wrong in my code. When I enter a search key which is a name that is not in the list, instead of printing the "Search Key: %s Not Found!", the program will just stop. How to fix it? Any suggestion on how can I improve my program?
#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
struct list
{
char name[20];
int age;
char gender[10];
struct list *next;
};
void main(void)
{
struct list *HEAD = NULL;
struct list *temp,*current, *trav;
struct list *prev,*temp1,*temp2;
char choice;
while(1)
{
clrscr();
printf("MENU\n");
printf("A) ADD\n");
printf("B) DISPLAY\n");
printf("C) DELETE\n");
printf("D) SEARCH\n");
printf("X) EXIT\n");
scanf("%c", &choice);
switch(toupper(choice))
{
case 'A':
temp= (struct list*)malloc(sizeof(struct list));
temp->next=NULL;
printf("Fill-Up the following:\n");
printf("Name:");
fflush(stdin);
gets(temp->name);
printf("Age:");
fflush(stdin);
scanf("%d",&temp->age);
printf("Gender:");
fflush(stdin);
gets(temp->gender);
if(HEAD == NULL)
{
HEAD = temp;
}
else if(HEAD!=NULL)
{
for(trav=HEAD; trav->next != NULL; trav= trav->next);
trav->next=temp;
}
else
{
printf("Not Enough Memory!\n");
}
break;
case 'B':
if(HEAD==NULL)
{
printf("Linked List is Empty!\n");
getch();
}
else{
for(trav=HEAD; trav != NULL; trav=trav->next )
{
printf("\nName: %s\n", trav->name);
printf("Age: %d\n", trav->age);
printf("Gender: %s\n\n", trav->gender);
}
getch();
}
break;
case 'C' :
temp1=( struct list*)malloc(sizeof(struct list));
temp1->next=NULL;
if(HEAD==NULL)
{
printf("No item to be delete. List is Empty!\n");
getch();
}
else {
printf("Enter The Name of the item you want to Delete: ");
fflush(stdin);
gets(temp1->name);
current=HEAD;
if(strcmp(temp1->name,current->name)== 0)
{
HEAD=HEAD->next;
free(current);
printf("Item has been successfully deleted from the list.\n");
getch();
}
else
{
for(prev=HEAD,trav=HEAD->next; strcmp(trav->name,temp1->name) == 1 ; trav=trav->next,prev=prev->next);
if(trav==NULL)
{
printf("Name: %s not found!", temp1->name);
getch();
}
else{
prev->next=trav->next;
free(trav);
printf("Item has been successfully deleted from the list.\n");
getch();
}
}
}
break;
case 'D':
temp2=( struct list*)malloc(sizeof(struct list));
temp2->next=NULL;
if(HEAD==NULL)
{
printf("No item to search. List is Empty.\n");
getch();
}
else{
printf("Enter Name (Search Key): ");
fflush(stdin);
gets(temp2->name);
int count=0;
struct list *trav2=HEAD;
while( trav2 !=NULL)
{
for(struct list *trav1=trav2; strcmp(trav1->name,temp2->name)!=0;trav1=trav1->next);
if(trav1!=NULL)
{
printf("\nName: %s\n", trav1->name);
printf("Age: %d\n", trav1->age);
printf("Gender: %s\n",trav1->gender);
trav2=trav1->next;
count++;
}
else {
trav2=NULL;
}
}
getch();
if(count==0)
{
printf("Search Key: %s Not Found!\n", temp2->name);
getch();
}
}
break;
case 'X':
if(HEAD!=NULL){free(HEAD); }
if(trav!=NULL){ free(trav); }
if(trav1!=NULL){ free(trav1); }
if(trav2!=NULL){ free(trav2); }
if(temp!=NULL){ free(temp); }
if(temp1!=NULL){ free(temp1); }
exit(1);
break;
}
}
}

Answer 1

In your search routine..
for(struct list *trav1=trav2; strcmp(trav1->name,temp2->name)!=0;trav1=trav1->next);
here trav1 will be null at the end of list but you are still going ahead and derefrencing it.
Add a check temp1 in your for loop like this:
for(struct list *trav1=trav2; trav1 && (strcmp(trav1->name,temp2->name)!=0);trav1=trav1->next);
Or, for better readability:
for (struct list *trav1 = trav2; trav1 != NULL; trav1 = trav1->next)
{
if (strcmp(trav1->name, temp2->name) !=0 )
break;
}
A few other comments on your code:
Do not use fflush(stdin) use something like this since that is not guaranteed by the standard to work.
int c;
while ((c = getchar()) != EOF && c != '\n')
;
Stop using gets(). It is impossible to use gets() safely. Use fgets() instead (but be aware it keeps the newline where gets() discards it).

Answer 2

Your loop continues while while( trav2 !=NULL). But where do you set trav2 = trav2->next? Without that, you loop will just continue forever.
But your code seems to have more problems than just that. Why are you allocating a new list item? Just declare a pointer to a list item (struct list*) and then point it to the head of your list.
for (temp = HEAD; temp != NULL; temp = temp->next)
{
// Examine temp for the value you are looking for
}
I suspect you are still new to understanding pointers. That is key to getting this code working right.