segmentation fault

[satyanagendra]

hi
I already write a database program in c and it is working fine. I change some modifications in the structure which holds the data in the database in that i got segmentation fault. the code is like this

struct student
{
int a;
char n[50];
student *nxt;
};
struct dummy
{
int a;
char n[50];
}

main()
{
student *head;
read(&head);
}

void read(student *head)
{
FILE *fp;
dummy s;
student *temp;
fp = fopen("trial.txt","rb");

while( fread(&s,sizeof(dummy),1,fp))
{
temp->a = s.a;
strcpy(temp->n,s.n);
temp->nxt = malloc(sizeof(student));
temp = temp->nxt;
}

fclose(fp);
}

the above code is working fine

but instead of int a in structure student if i place char p[20] reading from file gives segmentation fault. I write to file using fwrite function. But if i create pointer
instead of variable for struct dummy the problem solves i.e if write below code for reading it works.

void read(student *head)
{
FILE *fp;
dummy *s;
student *temp;
fp = fopen("trial.txt","rb");

while( fread(&s,sizeof(dummy),1,fp))
{
temp->a = s->a;
strcpy(temp->n,s->n);
temp->nxt = malloc(sizeof(student));
temp = temp->nxt;
}

fclose(fp);
}

If any body know the reason please tell me. If u dont understand my problem i will send total code to ur mail id if u give ur mail id .

thank u
regards
n s n reddy

[Meetee]

hi
I already write a database program in c and it is working fine. I change some modifications in the structure which holds the data in the database in that i got segmentation fault. the code is like this

struct student
{

}

Hi Satya,

Please give full code and give some details regarding problem.

Regards

[satyanagendra]

Hi Satya,

Please give full code and give some details regarding problem.

Regards

please give me ur mail id because code is in my pc but i am contacting u from my office system.

[Meetee]

please give me ur mail id because code is in my pc but i am contacting u from my office system.

I am sorry as I cannot give my mail id. It's also against forum rules being a member of TSDN. Your problem and solution can help many others on this forum. You better post your code snippet so others can also help you and refer your post.

Best regards,
Zodilla

[primeSo]

I am sorry as I cannot give my mail id. It's also against forum rules being a member of TSDN. Your problem and solution can help many others on this forum. You better post your code snippet so others can also help you and refer your post.

Best regards,
Zodilla

Ya, i would like to learn from this problem too.

[satyanagendra]

I am sorry as I cannot give my mail id. It's also against forum rules being a member of TSDN. Your problem and solution can help many others on this forum. You better post your code snippet so others can also help you and refer your post.

Best regards,
Zodilla

Actually it is a project the code is in totally 4 files can i paste all four files code here.

[xoinki]

hi,
I think you have not allocated for temp object. allocate using calloc or malloc.
if u declare a pointer you need to allocate memory before using it.

Thnks and Regards
xoinki

[satyanagendra]

hi,
I think you have not allocated for temp object. allocate using calloc or malloc.
if u declare a pointer you need to allocate memory before using it.

Thnks and Regards
xoinki

After allocating the memory to the pointer the problem was solved but my problem is when i am using a variable then only i get the segmentation problem

[xoinki]

hi,
Whether "p[20]" is enough? if u write more than 20 bytes.. obviously the program gives segmentation fault. I would suggest you to change all arrays to pointers then allocate, copy and finally cleanup module to free all loopin throgh the linked list.

Regards
Xoinki

[satyanagendra]

hi,
Whether "p[20]" is enough? if u write more than 20 bytes.. obviously the program gives segmentation fault. I would suggest you to change all arrays to pointers then allocate, copy and finally cleanup module to free all loopin throgh the linked list.

Regards
Xoinki

In p[20] i am using only 10 bytes. and the problem is while i am writing these records into the file using fread or fwrite here the program terminates with segmentation fault

[xoinki]

hi,
dont u think this ,

while( fread(&s,sizeof(dummy),1,fp))
 

should be

while( fread(&s,sizeof(dummy),1,fp) != EOF)
 

Regards,
Xoinki

[satyanagendra]

hi,
dont u think this ,

while( fread(&s,sizeof(dummy),1,fp))
 

should be

while( fread(&s,sizeof(dummy),1,fp) != EOF)
 

Regards,
Xoinki

ThankQ i will try it