i want to update records this code wroks some time but sometine not..please help me

[azmizryk]

void update()
{
	tyre rec;
	char id[10];
	int found=0;
	cout<<"\n\t\t\t*********************************\n";
	cout<<"\t\t\t\tUpdate a record.";	//heading
	cout<<"\n\t\t\t*********************************\n";
	cout<<"\n\t\t\tEnter the ID to update record.";
	cin>>id;
	fstream update("tyres record.txt",ios::in|ios::out);//open file for input & output.
	if(!update)	cout<<"\n\t\t\tError in opening file";
	else
	{
		cout<<"\t*****************************************************************\n";
		cout<<"\tID"<<setw(20)<<"Name"<<setw(20)<<"Size"<<setw(20)<<"Price\n";	//heading of table.
		cout<<"\t*****************************************************************\n";
		while(!update.eof() && found==0)
		{
			update>>rec.id>>rec.name>>rec.size>>rec.price;	//reading records.
			if(stricmp(rec.id,id)==0)	//matching record to update.
			{
				cout<<"\t"<<rec.id<<setw(20)<<rec.name<<setw(20)<<rec.size<<setw(15)<<rec.price<<endl<<endl;	//print matched one.
				found=1;		//terminate loop if found.
			}
		}
	}
	if(found==0)		//check if not found
		cout<<"\t\t\tRecord not exist..\n";
	else				//record found.
	{
		cout<<"\t\t\t**********Udate Information**********\n\n";	//take new data for founded record.	
		cout<<"\t\t\tEnter new ID:";			cin>>rec.id;	
		cout<<"\n\t\t\tEnter new name:";		cin>>rec.name;
		cout<<"\n\t\t\tEnter new size:";		cin>>rec.size;
		cout<<"\n\t\t\tEnter new price:";		cin>>rec.price;
		int pos=-1*sizeof(rec);		//find the location of founded record.
		update.seekp(pos,ios::cur);			//set pointer to founded location.
		update<<rec.id<<setw(20)<<rec.name<<setw(20)<<rec.size<<setw(15)<<rec.price<<endl;	//insert new data.
		cout<<"\n\t\t\tRecord updated...\n";
	}
	update.close();			//closing file.	
	cout<<"Press any key to continue";
	getch();
	system("cls");//clear the screen.
}//End of the function. 

[azmizryk]

it update some fields but some not...some time its update completely and sometime it updates but mix up the file..

[Felicia123]

all your name are in char?
not string?

[azmizryk]

yes all in character array...here

struct tyre		//declaring structure.
{
	char id[10],name[20],size[20],price[10];
};				//ending structure 

[bandicoot360]

You can not cin a char array, cin a string and then use c_str member function:

// ....
string id;
//...
cin >> id;
//...
while(!update.eof() && found==0)
		{
			update>>rec.id>>rec.name>>rec.size>>rec.price;	//reading records.
			if(strcmp(rec.id,id.c_str())==0)	//matching record to update.
			{ //...
			}
		}
//... 

[azmizryk]

Then ho to declared the structure?i need to use string on the place char?what is c_str?

[azmizryk]

It work it match the record and print bt when i update using pos variable it update on wrong position on file and sometimes id is nt updates rest are updated...here is the seekp problem i think

[bandicoot360]

Oh, I didn't notice first:
update>>rec.id>>rec.name>>rec.size>>rec.price;
This doesn' work.
You can use update.getline(rec.id, 10, '\n'); the third argument is the delimiting character which depends on how you store each field in the file, line by line for example?

For "getline" see: http://www.cplusplus.com/reference/istream/istream/getline/

[bandicoot360]

sizeof(rec) == 60, so you are always seeking 60 characters backwards. I'm not sure about your updating output, perhaps:
update<<setw(10)<<rec.id<<setw(20)<<rec.name<<setw(20)<<rec.size<<setw(10)<<rec.price<<endl;