Thread: printf acting strangely

Is there any way to clear the output stream?

Ok here's the problem.... I am wrinting a database system and I am using fscanf to grab records from a file. The problem is that when when i try to printf after the fscanf all the proper string isn't displayed but part of the data pulled from the file is. Here's my code:
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include "record.h"

int numRecords;

int main(void) {
FILE *fp;
int choice;

numRecords = 0;
initFILE(&fp, "a+");
countRecords(fp);
while (1) {
clrscr();
printf("Choose on of the following\n"
"0 - Enter a new record (at the end)\n"
"1 - Print all the records\n"
"2 - List accounts with zero balance\n"
"3 - List accounts with credit balances\n"
"4 - List accounts with debit balances\n"
"5 - List accounts with last names that begin with a letter\n"
"6 - List accounts with first names that begin with a letter\n"
"7 - List accounts with last names that match a name\n"
"8 - List accounts with first names that match a name\n"
"9 - Search by index\n"
"10 - Delete a record by index (totally removed, leaving no empty file space)\n"
"11 - Modify a record by index (leaving no empty file space)\n"
"12 - End of run\n"
"?: ");
scanf("%d",&choice);
switch (choice) {
case 0:
printf("\nENTER A NEW RECORD\n");
addRecord(fp);
++numRecords;
break;
case 1:
printf("\nPRINTING ALL RECORDS\n");
printRecords(fp);
break;
case 12:
fclose(fp);
printf("\nEXITING PROGRAM...");
return 0;
default:
printf("Invaild input. Please try again\n");
}
}

}

void anyKey() {
printf("\nPress any key to continue.");
getch();
}

void initFILE(FILE** fpp, mode m) {
char* filename ="";

printf("Please enter the name of the file to open: ");
scanf("%s",filename);

if((*fpp=fopen(filename,m)) == NULL) { /* Can't open file */
printf("ERROR: unable to open %s",filename);
exit(1);
}
else
printf("Opened file: %s\n",filename);
}

void addRecord(FILE* fp) {
Record client;
printf("\nPlease enter firstname, lastname, and balance: ");
scanf("%s%s%f",client.firstname,client.lastname,&c lient.balance);
fprintf(fp,"%d %s %s %.2f\n", numRecords, client.firstname, client.lastname, client.balance);
}

void countRecords(FILE* fp) {
Record client;

rewind(fp);
fscanf(fp,"%d%s%s%f",&client.index, client.firstname, client.lastname, &client.balance);
while (!feof(fp)) {
++numRecords;
fscanf(fp,"%d%s%s%f",&client.index, client.firstname, client.lastname, &client.balance);
}
printf("Number of Records: %d",numRecords);
anyKey();
}

void printRecords(FILE* fp) {
Record client;
printf("INDEX FIRST NAME LAST NAME BALANCE\n");
printf("---------------------------------------------\n");
rewind(fp);
fscanf(fp,"%d%s%s%f",&client.index,client.firstnam e,client.lastname,&client.balance);
while (!feof(fp)){
printf("%5d %12s %15s %10.2f\n",client.index,client.firstname,client.las tname,client.balance);
fscanf(fp,"%d%s%s%f",&client.index,client.firstnam e,client.lastname,&client.balance);
}
anyKey();
}

This only seems to happen after countRecords is run and the file actually contains records in it. Any thoughts? I think there is a problem with the countRecords() function.

Is there a way to read an entire line from the file at a time without using the function fread()?

> char* filename ="";
> printf("Please enter the name of the file to open: ");
> scanf("%s",filename);
Your code is broken here
Although you initialise the pointer (good), you initialise it with something which cant hold too many chars (none at all). In addition, it may also be non-writable, though it is in your case

char filename[100];
printf("Please enter the name of the file to open: ");
scanf("%s",filename);


> while (!feof(fp)) {
The dreaded !feof "bug"
See my "copy file" example here

You could write

Code:

while ( fscanf( fp, "%d%s%s%f",
        &client.index, client.firstname,
        client.lastname, &client.balance) != EOF  ) {

Which loops until end of file

Or perhaps with some error checking

Code:

while ( fscanf( fp, "%d%s%s%f",
        &client.index, client.firstname,
        client.lastname, &client.balance) == 4  ) {

Which loops until either EOF, or a bad record is found

Noting your first bug, are client.firstname and client.lastname arrays (char[]) or pointers (char*). Because they need to be arrays.