sorting and functions/structures

[Alfy]

#include <stdio.h>
#include <string.h>

int i,k,type;
char buffer[100],l,line[50];

struct  student
{
    char name[20];
    int age;
    int id;
};
struct student st[2],temp,*sp;

int sort(struct student *p)
{
    *sp=st[0];
    p->age;
for(i=0; i<l; i++)
    {
        if(st[i].age<st[i+1].age)
        break;
         else
        if(st[i].age>st[i+1].age)
        {
            temp=st[i];
            st[i]=st[i+1];
            st[i+1]=temp;
        }break;
    }   
    printf("\t\tsorted student information\n--------------------------\n");
    printf("%d",st[i].age);
    return(0);
}

int main()
{
    for(i=0;i<3;i++)
    { 
        printf("please enter your name:\n");
        fgets(st[i].name,sizeof(st[i].name),stdin);
        printf("please enter your age:\n");
        fgets(buffer,sizeof(buffer),stdin);
        sscanf(buffer,"%d",&st[i].age); 
        printf("please enter your id:\n");
        fgets(buffer,sizeof(buffer),stdin);
        sscanf(buffer,"%d",&st[i].id);
    }   
        while(1)
        {
            printf("Please enter the # for the program you want to run:\n");
            fgets(line,sizeof(line),stdin);
            sscanf(line,"%d",&type);
            if(type==5)
            break;
            switch(type)
            {

            case 1:/*sort by name */
                sort(sp);
                break;
            case 2:/* sort by age  */
                sort(sp);
                break;
            case 3:/* sort by id   */
                sort(sp);
                break;
            case 4:
                printf("1-sort by name\n2-sort by age\n3-sort by id\n4-help\n5-Quit\n");
                continue;

            default:
                printf("enter 4 for help\n");
                continue;
            }
        }                           
return(0);    
}

ok, so this is kinda a repost, but with different problems. whats going on is the user needs to input students information(name, age, and id) the there is a switch case so that the data entered can be sorted by either name, age or id. right now its only set up to sort by age, and doesnt work, i get a segmentation error in the unix editor. So, i was wondering what i did wrong(im sure there are more than one error) and if i need to write three different functions for each sort.

[jasweb2002]

Where is the problem occuring? Have you done any debugging at all? Do your records that you attempt to sort even exist?

[Narue]

>i was wondering what i did wrong
Start by getting the sorting algorithm correct with simple test cases. All of the framework is only going to make debugging harder. But I can tell you right now that your algorithm is wrong. Check my sorting routines entry in the Code Snippets section for ideas.

>if i need to write three different functions for each sort
For age and id you could get away with using a single sort function, but for strings you'll either need another function that handles strings properly, or pass a comparison function as an argument like qsort does.

[Alfy]

i really have no idea what u mean by debugging, i dont know where the problem is occuring b/c all it says is segmentation fault, and i dont really know what that is, where do i get records of sorting?

[Alfy]

k, thanks!

[Alfy]

Where is the problem occuring? Have you done any debugging at all? Do your records that you attempt to sort even exist?

what is a segmentation error?

[Chainsaw]

Ususally it means you referenced a pointer that is NULL or uninitialized. In your case, 'sp' appears to be an uninitialized pointer.

[jwenting]

If you don't know what debugging is you should look up about that first and start to practice it...