i/o stuff

I'm trying to read a file I text file I created in notepad. Can it read notepad files? Does the file have to be in a certain place in order for the program to find it?
My code:

Code:

---

#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char *argv[])
{
    char str[100];
   
    ifstream a_file ("hi.txt");
    a_file>>str;
    cout<<str<<"/n";
   
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

My result:
α╒÷w< "/nPress any key to continue . . .

Whats wrong? How do I fix it?

Well I'd say it never opened the file at all, and what you're seeing is the random junk which was in str right at the start of the program.

Either make sure the file is in the directory which the program thinks is the current directory, or specify an absolute path to the file.

notepad creates simple text files (I believe) and so a simple program like yours should be able to open and read the data contained within.

Quote:

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Originally Posted by cerin

Whats wrong?

---

At least three things.

1) "/n" should be "\n" I'm guessing.
2) You never test whether the file was opened or not... if not, then the output you provided could be the result of random data present in the array.
3) You should probably use one of the get or read member functions provided by the ifstream object to make sure you aren't getting more data than your program (the array) can handle.

Beyond that, what does the file look like when you open it in notepad?

All my file says in notepad is:

hi
hi
hi
hi
hi
hi

First make surethe file has opened properly by checking the fail() method:

Code:

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std::ifstream file("myfile.txt");
if(file.fail()) return 0;

---

Then to read a word from the file:

Code:

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std::string word;
file >> word;

---

Or to read a line from the file:

Code:

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std::string line;
std::getline(file, line);

---

Or to read the entire file:

Code:

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//Get size of file
file.seekg(0, std::ios::end);
int size = file.tellg();
char* buffer = new char[size + 1];

//Read from file
file.seekg(0, std::ios::beg);
file.read(buffer, size);

//End string with NULL terminator, just in case...
buffer[size] = '\0';

---

Will this work for checking if the file is open?

Code:

---

#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char *argv[])
{
    char str[100];
   
    ifstream a_file ("hi.txt");
    if (!a_file.is_open()){
    cout<<"File isn't open.";
    }
    else{
    a_file>>str;
    cout<<str<<"/n";
    }
   
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

Edit: forgot curly brace after cout

This is my new code:

Code:

---

#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char *argv[])
{
    char str[100];
   
    ifstream a_file ("hi.txt");
    if (!a_file.is_open()){
    cout<<"File isn't open.";
    }
    else{
    a_file>>str;
    cout<<str<<"\n";
    }
   
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

Is there any easy way to read the entire file than the one below? So I only have to change a few things?? Or at least a couple lines instead of one?

Quote:

---

Code:

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//Get size of file
file.seekg(0, std::ios::end);
int size = file.tellg();
char* buffer = new char[size + 1];

//Read from file
file.seekg(0, std::ios::beg);
file.read(buffer, size);

//End string with NULL terminator, just in case...
buffer[size] = '\0';

---

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Quote:

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Is there any easy way to read the entire file than the one below?

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Not with >> operator. That operator is for reading what's called 'formatted' input. What that means is the >> operator takes certain predefined actions when it comes across whitespace(spaces, tabs, newlines) in your input file. One of the predefined actions the operator >> takes is to stop reading data when it encounters trailing whitespace, e.g a space or a newline character('\n'). The >> operator is also defined to skip any leading whitespace. So, if the >> operator is reading a line in your file it keeps reading characters until it comes to a whitespace character and then stops. The next time the >> operator is called, it skips leading whitespace until it finds some characters, and then it reads in characters until it comes to another whitespace. In that manner, the >> operator is said to treat the data in the input file as 'formatted' data, i.e. the data is formatted as words.

If you use the get() and getline() functions, you can read in different amounts of input, and they treat the input file as 'unformatted' input. As a practical matter, that just means the get() and getline() functions have different rules on how much input they will read in. Generally, the way it works is they treat whitespace just like any other character, so whitespace does not necessarily cause reading to stop( as it will with the >> operator).

The designation 'unformatted' or 'formatted' input doesn't mean the input file looks any different. For instance, this data

apple pear cherry

can be either formatted input or unformatted input--it just depends on whether you are using the >> operator which reads in input one word at a time, or you are using the get() functions which treat the data as one continuous string of characters.

In your program, you could use the getline() function for a string:

string str;
getline(inFile, str);

The getline() function has a third parameter which indicates the 'delimiter'. A 'delimiter' tells the function when to stop reading data. The default value is '\n'. So, the function above will stop reading characters into the string str when it comes upon a '\n' character. However, you can set that delimiter to anything you want:

string str;
getline(inFile, str, '#');

I that case, getline() will continue reading characters from the file until the '#' character is encountered--even across multiple lines. You can put the character at the end of the file, and getline() will read the whole file into the string str.

Quote:

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Originally Posted by cerin

Is there any easy way to read the entire file than the one below? So I only have to change a few things?? Or at least a couple lines instead of one?

---

If you are simply trying to store the entire contents of a text file in a mass buffer of some kind in as few steps as possible then there are at least a couple of options for you:

You could store everything in a string:

Code:

---

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <iterator>

int main()
{
    std::string str;
    std::ifstream input("hi.txt");

    // Read entire file into string container...
    input.unsetf(std::ios::skipws);  // Preserve/store whitespace characters
    std::copy(std::istream_iterator<char>(input),std::istream_iterator<char>(),
              std::inserter(str,str.end()));

    // Output file contents to cout...
    std::cout << str << std::endl;

}

---

You can also use a stringstream:

Code:

---

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>

int main()
{
    std::stringstream str;
    std::ifstream input("hi.txt");

    // Read entire file into stringstream...
    str << input.rdbuf();

    // Output file contents to cout...
    std::cout << str.str() << std::endl;

}

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Given a file hi.txt containing the following:

Code:

---

hi there
hi there
hi there
hi there

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Then of course the output should be:

Code:

---

hi there
hi there
hi there
hi there

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How do I make it display the text that the program read? could you fit it into the code Magos gave me plz?

Have you gotten anything to work?

If you are using windows, you will need to do something like this to the file name:

fstream inFile("C:\\Beginning C++\\data.txt");

You can read in some data and output it doing something like this:

string str;
inFile>>str;
cout<<str<<endl;

As I explained in my previous post, that will read in one word. I also explained in my previous post how you can read in the whole file.

This is my code:

Code:

---

#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main(int argc, char *argv[])
{
    char str[100];
   
    ifstream a_file("hi.txt");
a_file.seekg(0, std::ios::end);
int size = a_file.tellg();
char* buffer = new char[size + 1];

//Read from file
a_file.seekg(0, std::ios::beg);
a_file.read(buffer, size);


//End string with NULL terminator, just in case...
buffer[size] = '\0';



    system("PAUSE");
    return EXIT_SUCCESS;
}

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Sorry, but I don't want to know how to read 1 word or line.
It reads the file, but how do I get it to display it?

Have you been introduced to cout yet? It's usually one of the first things you learn--otherwise you couldn't run programs that displayed anything. Use cout to display the variable with the data in it. Or, do you not know which variable has the data in it? If you don't understand the code you posted, maybe you should use a simpler method as outlined at the end of my previous post.

Yes I've been introduced to cout. I don't understand what variable.

I put in:

Code:

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cout<<a_file;

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It diplays 0.
I put it right below

Code:

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a_file.read(buffer, size);

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Well, according to the code you just brute force copy and pasted the pointer containing the data you read is called buffer. May I refer you to your code:

Quote:

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a_file.read(buffer, size);

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That statement reads size bytes into buffer. Cerin, is this a language barrier problem or do you not understand the code?

I don't understand the part magos posted. Which of course is the majority of it. I would appreciate you explaining it.

It sort of works now. It displays the file but it also displays USERDOMAIN=RE_ after the document. How do I fix that??

OK, so the code is not that hard really. We will look at it piece by piece.

1. Create a pointer of type character to hold the file. We will initially set this pointer to NULL.

Code:

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[COLOR=Bluechar[/COLOR]* myFileBuffer = NULL;

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2. Lets create an integer to hold the determined size of the file:

Code:

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int myFilesize;

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3. Lets open a file:

Code:

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myFile.open("myFile.txt", ios_base::in);

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4. This is where it gets a little confusing for some people. We need to determine the size of the file so we know how much to read. In order to do
this we are going to take advantage of two members of fstream, seekg and tellg.

a. seekg places the current position in the stream. So if we did something like this:

Code:

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myFile.seekg(0, ios_base::end);

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we would move 0 char away from the end of the file. Similarly if we did something like this:

Code:

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myFile.seekg(2, ios_base::beg);

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We would move 2 char away from the begginning of the file, aka we would skip the first two characters.

b. tellg() is even simpiler. It returns the current position of the stream pointer. Thus if we did this:

Code:

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myFile.seekg(2, ios_base::beg);
cout << myFile.tellg();

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We would recieve the value of 2. (Numbers start at 0).

Alright now with that discussed one can see that to determine the length of a file you would
simply place the stream input at the end of the file and then ask for the number of characters skipped.

Code:

---

myFile.seekg(0, ios_base::end);
myFilesize = myFile.tellg();

---

5. Now that we know how large the file is, we need to allocate enough memory in our buffer to hold the file. We accomplish this by using new:

Code:

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myFileBuffer = new char[myFilesize];

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6. With the memory allocated now it is time to read the file into our buffer. However remember that
we moved the file pointer to the end of the file, so the first thing we need to do is move it back to the begginning of the file:

Code:

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myFile.seekg(0, ios_base::beg);

---

7. Now we read the file into our buffer:

Code:

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myFile.read(myFileBuffer, myFilesize);

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8. Like all good strings we need to ensure that they end with '/0'. So we add it to the end of the string:

Code:

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myFileBuffer[myFilesize] = '\0';

---

9. And finally we print out the contents of our file buffer with cout:

Code:

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cout << myFileBuffer << endl;

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Code:

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It sort of works now. It displays the file but it also displays USERDOMAIN=RE_ after the document. How do I fix that??

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