c++ fstream when see string in file [closed] - c++

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I made a code but it doesn't work.Can you help? In code, I wanted to take a line and if code see //n, end line.
Here is my example.
File:
I love C++! //n
My Code:
ifstream file("file.txt");
char text[250];
while(file >> text){
cout << text << " ";
if(text == "//n"){
cout << endl;
}
}
Thanks for your help.

Answer 1

I am unsure as to what you are trying to do, however it seems that you want to get a line worth of text. If so, you would want to change
char text[255];
....
if(text == "//n")
to
std::string text;
...
if(text == "\n")
The array comparison will not compare strings. So use the std::string to allow you to use == operator.
As C++ special character codes use a backslash rather than two forward slashes.
However, I'd also suggest using a single char rather than an array (as indexing doesn't seem to be a concern since you only access the first character in it).

Answer 2

If you want to read a file a word at a time:
ifstream file("file.txt");
std::string line;
while(std::getline(file, line)) {
std::stringstream linestream(line);
std::string word;
while(linestream >> word) {
std::cout << "Word: " << word << " ";
}
std::cout << "EOL\n";
}
Basically your code has a couple of issues.
'//n' is not a special character we all assume you meant '\n'.
Most operators that read text from a file will disgard the '\n' character.
operator>> will disguard white space (including \n).
getline() reads the line but drops the \n.
Thus '\n' is never in text to be compared too.
Arrays char text[255] will convert themselves into pointers easily.
Thus the comparison you are doing compares two pointers. This will never be equal.
You need a type that does something smart with == so that you compare the text.
For this you should use std::string.
As a good style guide.
Never put using namespace std; in your code. It causes more trouble when you have anything but a simple bit of throwaway code. And using it in simple throwaway code is a bad habit that will catch up to you someday.
The reason std (as well as others) is short and not standard is so that prefixing it items from the standard library is not burdensome.
std::cout << text << " "; // not hard.
std::cout << std::endl;
There is no real reason to use std::endl (debugging being an exception I suppose). In normal situations the extra flush it adds will generally cause the output to slow down perceptibly. So prefer to use '\n' unless you specifically want to force a flush.

Answer 3

The problem here is, your code compares pointers, instead of comparing strings (as noted also in the other answer):
if(text == "//n")
{
...
}
Here text is a pointer (actually, an array of char, but in this context it's equivalent to a pointer), and "//n" also is a pointer (also an array). Comparing two pointers is not what you want.
To fix your code so it compares strings, one of the things your code compares should be a string instead of a pointer. To mark "//n" as a string, append s to it:
if(text == "//n"s)
{
...
}
This is a bit obscure; another solution is to make text a string (as described in the other answer):
std::string text;