Find specifi ID info using structure - c

Question

I could not find specific student_Id info from a rage of given info.suppose, I am taking input from 1 to 100 all student info. now I want to find only 50th number student_ID all info.i could not do it. how it possible.here show my code. what's wrong with my code and how fixed it.thanks
# include <string.h>
# include <stdio.h>
# include <stdlib.h>
# include <conio.h>
struct student
{
char student_id[100];
char name[10];
int m[50],credit[100],sub[100];
int total,sumCredit;
float GP[100];
char result[5];
char grade[100][10];
double sumCreditxGP;
}*p,*s;
float gradesToGP(float marks);
char *markToG(float gp);
void lines(void);
void main()
{
int i,j,l,n,sub,k;
// clrscr();
printf("Enter the no. of students : ");
scanf("%d",&n);
p=(struct student*) malloc(n*sizeof(struct student));
//printf("%d",p);
//exit(0);
s=p;
for(i=0; i<n; i++)
{
printf("Enter a student id : ");
scanf("%s",&p->student_id);
printf("Enter a name : ");
scanf("%s",&p->name);
printf("Enter the no. of subject : ");
scanf("%d",&p->sub[i]);
p-> total=0;
p-> sumCredit=0;
p-> sumCreditxGP=0;
l=0;
for(j=0; j<p->sub[i]; j++)
{
one:
printf("Enter Marks of %d Subject\t%d : ",j+1,p->sub[i]);
scanf("%d",&p->m[j]);
printf("Enter Credit Hour: ");
scanf("%d",&p->credit[j]);
p->GP[j] = gradesToGP((float)p->m[j]);
strcpy(p->grade[j],markToG(p->m[j]));
if((p->m[j])>100)
{
printf("---------------Wrong Value Entered-----------\n");
goto one;
}
p->total+=p->m[j];
p->sumCredit+=p->credit[j];
p->sumCreditxGP+=p->credit[j]*p->GP[j];
if(p->m[j]<40)
l=1;
}
if(l==0)
strcpy(p->result,"PASS");
else
strcpy(p->result,"FAIL");
p++;
}
char search_id[10];
printf("Enter id to find specific student ");
scanf("%s",search_id);
//PROBLEM START HERE
for(i=0; i<n; i++)
{
if(p->student_id==search_id){
printf("found");
printf("%s",s->student_id);
}else{
printf("Not found");
}
s++;
}
getch();
}
float gradesToGP(float marks)
{
if (marks>=80 && marks<=100)
{
return(float)4.00;
}
else if (marks>=75 && marks<=79)
{
return(float)3.67;
}
else if (marks>=70 && marks<=74)
{
return(float)3.33;
}
else if (marks>=65 && marks<=69)
{
return(float)3.00;
}
else if (marks>=60 && marks<=64)
{
return(float)2.67;
}
else if (marks>=55 && marks<=59)
{
return(float)2.33;
}
else
{
return(float)5.00;
}
}
char *markToG(float marks)
{
if (marks>=80 && marks<=100)
{
return "A";
}
else if (marks>=75 && marks<=79)
{
return "A-";
}
else if (marks>=70 && marks<=74)
{
return "B+";
}
else if (marks>=65 && marks<=69)
{
return "B";
}
else if (marks>=60 && marks<=64)
{
return "B-";
}
else if (marks>=55 && marks<=59)
{
return "C+";
}
else
{
return "null";
}
}
void lines(void)
{ printf("**********************************************************************");
}
Please tell me how can I fixed it.thanks in advanced.

Answer 1

if(p->student_id==search_id){
printf("found");
Now, that's not how you compare strings in C. Use the strcmp() function for string comparison. You may read about strcmp() here.

Answer 2

The issue is your equality check: if(p->student_id==search_id)
Because both student_id and search_id are char arrays, the types will decay to pointers (char *) and this will never work as you expect. Instead, you need to use strcmp (or better, strncmp).
if(strncmp(p->student_id, search_id, 10) == 0) { /* equality */ }