At 1/24/2007 01:08 PM, you wrote:
>Hey, I have a problem in linked list. I made a little database that
>stores name and secret number. But the problem is that when I want to
>save these data in any file so this data saves but real problem is to
>read data from a file. I had posted earlier this problem on this
>group.Hope I have reached to my answer. Plz solve my problems. Here is
>my code
Well, for one, you never initialize ptrthis. But why do that if all
you want to to do is print the values? Here's a quick and dirty
re-work of rfile:
void rfile(){
biodata TEMP;
FILE *fptr; /*file ponter*/
if( (fptr=fopen(MyFile,"rb")) == NULL) /*if returning NULL*/
printf("Can't open file %s", MyFile);
while(fread(&TEMP, sizeof(biodata), 1, fptr) == 1){ /*item
return or found*/
printf("\nName: %s", TEMP.name); /*print contents*/
printf("\nNumber: %03d\n", TEMP.num);
}
fclose(fptr);
}
~Rick
>#include <stdio.h>
>#include <conio.h>
>#include <stdlib.h>
>
>#define TRUE 1
>
>void newname();
>void listall();
>void rfile();
>
>struct biodata{
> char name[30];
> int num;
> biodata *ptrnext;
>};
>biodata *ptrfirst, *ptrthis, *ptrnew;
>
>void main(void){
>
>
> ptrfirst = (struct biodata *) NULL;
>
> while(TRUE){
> printf("\nPress 'e' for new entry.\n");
> printf(" 'l' for list all.\n");
> printf(" 'r' for read.\n");
> printf(" 'q' for quit");
> char ch;
> ch=getch();
>
> switch(ch){
>
> case 'e':
> newname(); /*Enter new name*/
> break;
>
> case 'l':
> listall(); /*List entire agents*/
> break;
>
> case 'r':
> rfile(); /*Read data from file*/
> break;
>
> case 'q':
> exit(0);
> break;
> }
> }
>}
>
>void newname(){
>
> char numstr[15];
> ptrnew = (struct biodata *) malloc (sizeof(biodata)); /*Gets memory
>space */
>
> if(ptrfirst == (struct biodata *)NULL) /*if none already*/
> ptrfirst = ptrthis = ptrnew; /*save address*/
>
>/*not first item*/
> else{
> /*go to end of list*/
> ptrthis =
> ptrfirst;
> /*Start at begin*/
> while(ptrthis->ptrnext != (struct biodata *)NULL ){
> ptrthis = ptrthis->ptrnext; /*find next item*/
> }
> ptrthis->ptrnext = ptrnew; /*point to new item*/
> ptrthis = ptrnew; /*go to new item*/
> }
> FILE *fptr;
> if( (fptr=fopen("E:/MS Visual Studio/link list/biodata.txt", "a")) ==
>NULL)
> printf("Can't open File.");
>
> printf("\nEnter name: ");
> gets(ptrthis->name);
> printf("Enter number: ");
> gets(numstr);
> ptrthis->num = atoi(numstr);
> fwrite(ptrthis, sizeof(biodata), 1, fptr);
> fclose(fptr);
> ptrthis->ptrnext = (struct biodata *) NULL;
>}
>
>void listall(){
>
> if(ptrfirst == (struct biodata *)
> NULL) /*if empty list*/
> printf("\nList is
> Empty."); /*return*/
>
> ptrthis = ptrfirst; /*start at first item*/
> while(ptrthis != (struct biodata *) NULL){ /*print contents*/
> printf("\nName: %s", ptrthis->name);
> printf("\nNumber: %03d\n", ptrthis->num);
> ptrthis = ptrthis->ptrnext; /*move to next item*/
> }
>
>}
>
>void rfile(){
>
> FILE *fptr; /*file ponter*/
> if( (fptr=fopen("E:/MS Visual Studio/link list/biodata.txt","r")) ==
>NULL) /*if returning NULL*/
> printf("Can't open file");
>
> while(fread(ptrthis, sizeof(biodata), 1, fptr) == 1){ /*item return
>or found*/
> printf("\nName: %s", ptrthis->name); /*print contents*/
> printf("\nNumber: %03d\n", ptrthis->num);
> ptrthis = ptrthis->ptrnext;
> }
> fclose(fptr);
>}
>
>
>
>
>
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>
>
>
