Reading characters from a file

[nizbit]

I am having a little bit of a dilemma. I have an input file that can have a number 1 through 9 or a asterisk. I am treating 1-9 as a character. I don't know if there is white space or new lines. I can't use >> because I don't know if there is white space. I can't use get() because it will stop reading in characters if get encounters a new line. Could someone give me some suggestions?

[mcriscolo]

Generally speaking, if you're not sure of the contents of the file, or if it may contain undesired characters, you should consider reading a line of the file into a string variable or char array, and then cleaning it up (removing leading/trailing spaces, CR/LF, etc.). Then you can look at converting the string/char data to a form that your program can use.

[stilllearning]

Additionally, you can also paste some of your file contents here, and any code you have here, we can give you better ideas on how to proceed.

[nizbit]

This is what I came up with, but the output is all zeros

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

int main(int argc, char *argv[])
{
	//Testing for correct number of arguments at command line
	if(argc != 3)
	{
		cout << "ERROR--Not enough arguements!!" << endl;
		cout << "The correct format is: \"./name of program\" \"input file\" \"output file\"" << endl;
		//exit(1);  change at submission
	}
	
	//opening data file from user at run time
	ifstream infile;
    infile.open(argv[1]);
	
	if(infile.fail())
	{
		cout << "Failed to open input file." << endl;
		exit(1);
	}

	ofstream outfile;
    outfile.open(argv[2]);
	
	if(outfile.fail())
	{
		cout << "Failed to open output file." << endl;
		exit(1);
	}

	const int SIZE = 81;

	int board[SIZE];
	char input[1];
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
			if (infile.peek()=='\n') 
			    infile.ignore(1,'\n');
			else if (infile.peek()==' ') 
			    infile.ignore(1,' ');
			infile.get(input, 1);
			board[i*9+j] = atoi(input);
		}
	}
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
			cout << board[i*9+j];
		}
		cout << endl;
	}
	cout << endl;
	system("pause");
	return 0;
}

input file

* 1 * 4 * * * * 2
* * 4 * 7 2 * * *
* 8 3 * * 5 * 7 *
* 3 8 2 * 7 * * *
* 5 2 1 * 4 8 3 *
* * * 5 * 3 7 2 *
* 2 * 3 * * 9 4 *
* * * 7 2 * 6 * *
9 * * * * 6 * 1 *

[VernonDozier]

I am having a little bit of a dilemma. I have an input file that can have a number 1 through 9 or a asterisk. I am treating 1-9 as a character. I don't know if there is white space or new lines. I can't use >> because I don't know if there is white space. I can't use get() because it will stop reading in characters if get encounters a new line. Could someone give me some suggestions?

No, get will read in a newline character as a newline character. Not sure what you mean by "stops". If you use get to read in a char, it "stops" after every character.

ifstream ins;
char c;
ins.get (c);

Also, are you trying to save the spaces and newlines or you just want to ignore them? If you need to save them, you're right, don't use >>. If you want to ignore spaces and newlines, which it looks to me like you want to, >> is perfect.

This is what I came up with, but the output is all zeros

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

int main(int argc, char *argv[])
{
	//Testing for correct number of arguments at command line
	if(argc != 3)
	{
		cout << "ERROR--Not enough arguements!!" << endl;
		cout << "The correct format is: \"./name of program\" \"input file\" \"output file\"" << endl;
		//exit(1);  change at submission
	}
	
	//opening data file from user at run time
	ifstream infile;
    infile.open(argv[1]);
	
	if(infile.fail())
	{
		cout << "Failed to open input file." << endl;
		exit(1);
	}

	ofstream outfile;
    outfile.open(argv[2]);
	
	if(outfile.fail())
	{
		cout << "Failed to open output file." << endl;
		exit(1);
	}

	const int SIZE = 81;

	int board[SIZE];
	char input[1];
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
			if (infile.peek()=='\n') 
			    infile.ignore(1,'\n');
			else if (infile.peek()==' ') 
			    infile.ignore(1,' ');
			infile.get(input, 1);
			board[i*9+j] = atoi(input);
		}
	}
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
			cout << board[i*9+j];
		}
		cout << endl;
	}
	cout << endl;
	system("pause");
	return 0;
}

input file

* 1 * 4 * * * * 2
* * 4 * 7 2 * * *
* 8 3 * * 5 * 7 *
* 3 8 2 * 7 * * *
* 5 2 1 * 4 8 3 *
* * * 5 * 3 7 2 *
* 2 * 3 * * 9 4 *
* * * 7 2 * 6 * *
9 * * * * 6 * 1 *

You can read in a character at a time, rather than read in an entire string. The spaces are no longer an issue if you read from the file into a character rather than a string. Here you have defined the variable you are reading into a character array of length 1:

char input[1];
// code
infile.get(input, 1);

Just make input a char.

char input;
// code
infile.get(input);

But frankly I think you are making it more complicated than it needs to be. You mentioned that you want to store 1 - 9 as characters, as well as store the asterisk as a character, but you have board defined as an integer array, then you are trying to do something with atoi. If I understand what you are trying to do correctly, all you need to do is this:

char board[SIZE];
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
                       infile >> board[i * 9 + j];
		}
	}

[nizbit]

No, get will read in a newline character as a newline character. Not sure what you mean by "stops". If you use get to read in a char, it "stops" after every character.

ifstream ins;
char c;
ins.get (c);

I was a little confused on what get() could do. I thought it would stop reading characters at a newline.

Also, are you trying to save the spaces and newlines or you just want to ignore them? If you need to save them, you're right, don't use >>. If you want to ignore spaces and newlines, which it looks to me like you want to, >> is perfect.

You can read in a character at a time, rather than read in an entire string. The spaces are no longer an issue if you read from the file into a character rather than a string. Here you have defined the variable you are reading into a character array of length 1:

char input[1];
// code
infile.get(input, 1);

Just make input a char.

char input;
// code
infile.get(input);

I want to ignore spaces, but I don't know if the file will contain spaces. I cannot make any assumptions on how the input file is formatted.

But frankly I think you are making it more complicated than it needs to be. You mentioned that you want to store 1 - 9 as characters, as well as store the asterisk as a character, but you have board defined as an integer array, then you are trying to do something with atoi. If I understand what you are trying to do correctly, all you need to do is this:

char board[SIZE];
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 9; j++)
		{
                       infile >> board[i * 9 + j];
		}
	}

I have to read the file as characters because I need to input the asterisk. Then I'm using atoi() to convert the characters to integers. Also if atoi() comes across a character that it does not know how to convert, it will convert it to a zero which I need.

[VernonDozier]

I want to ignore spaces, but I don't know if the file will contain spaces. I cannot make any assumptions on how the input file is formatted.

>> ignores spaces and newlines. Thus if each element of your matrix is a single asterisk or digit, >> is perfect for your needs. If a number can be two or more digits, >> with a char won't be as good.

I have to read the file as characters because I need to input the asterisk. Then I'm using atoi() to convert the characters to integers. Also if atoi() comes across a character that it does not know how to convert, it will convert it to a zero which I need.

Fine, but how are you STORING the data? As an integer array or as a char array? As I said above, if all the data is singe digits or an asterisk, you can read it in as a char with the >> operator. No need to use atoi. A quick conversion from char to int would do fine. You could also use atoi too. If you are storing it as an integer array, you can read it in to a dummy char variable, then convert and store in in the integer array. There's more than one way to do this.