File handling case

[shoaib yehya]

File Head Program
Write a program that asks the user for the name of a file. The program should display the first 10 lines of the file on the screen (the “head” of the file). If the file has fewer than 10 lines, the entire file should be displayed, with a message indicating the entire file has been displayed.

Need help and guidance in code, it doesn't display on the content of the file.

int main()
{
	fstream file;
	int max=0;
	string str;	
	file.open("name.txt", ios::in);
	if(file.fail())
	{
		cout<<"file is not open"<<endl;
	}	
	while(getline(file, str))
	{
		max++;
	}
	cout<<"number of line are "<<max<<endl;	
	while(getline(file, str))
	{
		cout<<str<<endl;
		if(max>=10)
		{
			break;
		}
	}
	file.close();
}

[ne555]

your code, indented

int main() {
	fstream file;
	int max = 0;
	string str;

	file.open("name.txt", ios::in);
	if(file.fail()) {
		cout << "file is not open" << endl;
	}

	while(getline(file, str)) {
		max++;
	}
	cout << "number of line are " << max << endl;

	while(getline(file, str)) {
		cout << str << endl;
		if(max >= 10) {
			break;
		}
	}
	file.close();
}

look at lines 11 and 16
for the loop in line 11 to end, the reading operation must fail, so I don't understand how you expect it to work later at line 16

[shoaib yehya]

alright, its mean, line 11 makes program to come at the end of the file ??
after the in line 16 it will get nothing ?
can you guide me what to do here ?
i just sollved it with

while(getline(file, str))
	{
		max++;
	}
	cout<<"number of line are "<<max<<endl;
	file.close();
	
	file.open("name.txt", ios::in);
	if(!file.fail());
	for(int index=0; index<=max; index++)
	{
		getline(file, str);
		cout<<str<<endl;
		if(max>=10)
		{
			break;
		}
	}
	file.close();
}

i just closed the file and then reopen it and read again from start,, but it doesn't look elegant can you suggest or give hint for another way ?

[Handy Andy]

Hello shoaib yehya,

PLEASE ALWAYS USE CODE TAGS (the <> formatting button), to the right of this box, when posting code.

Along with the proper indenting it makes it easier to read your code and also easier to respond to your post.

http://www.cplusplus.com/articles/jEywvCM9/
http://www.cplusplus.com/articles/z13hAqkS/

Hint: You can edit your post, highlight your code and press the <> formatting button.
You can use the preview button at the bottom to see how it looks.

I found the second link to be the most help.

First you missed the include files at the top of your program. It is best to include the whole program so people do not have to guess at what you did.

As ne555 has pointed out the first while loop reads you file until the "eof" bit is set on the stream. When you reach the second while loop the stream is in a failed state and the second while loop does not work.

before the second while loop you need to reset the state bits on the stream and reposition the file back to the top before you can read it again.

For the if statement if(max >= 10). Really. Unless it is a short file "max" is always going to be "> 10". When I first ran the program it printed one line and left the while loop.

In the instructions I see that you have to prompt the user to enter a file name, which you have not done. And if less than ten lines are in the file that you should print a message that the entire file has printed, which you have not done. No where did I see where you have to count the maximum number of lines in the file.

Your program could be done with this:

if (!inFile)
{
	std::cout << "\n    file \"" <<inFileName<<"\" did not open." << std::endl;
	return 1;
}

for (size_t lc = 0; std::getline(inFile, str) && lc < MAXLINES; lc++)
{
	std::cout << str << std::endl;
	count++;
}

if (count < MAXLINES)
	std::cout << "\n Entire file has printed.\n" << std::endl;

Hope that helps,

Andy

[Handy Andy]

Hello shoaib yehya,

Instead of closing and reopening the file you can use:

inFile.clear();
inFile.seekg(0);

The first line resets the state bits on the stream and the second moves the file pointer back to the beginning of the file.

Andy

[shoaib yehya]

Hey Andy and Ne555.

Thank you so much for guidance. I just edited the code and indented the code.
I am expecting it is visible properly now.

Thanks for the guideline. If I found any problem I will revert back to you.

Regards.