C ++如何逐字（字符串）读取文件，但将其显示为与文本文件完全相同

Question

I'm having trouble figuring out how to get newlines to display when outputting text to cmdPrompt. The .text file is something like this:

"Roses are red
 violets are blue
 sugar is sweet
 and so are you"

And my code for the loop is:

#define newLn "\n"
ifstream ins; //these two are near the top where the programs opens the file

string aString;      

while(ins >> aString){
        if(aString != newLn){
        cout << aString << ' ';
        }
        else
            cout << endl;
   }

It reads in the text fine but it just displays it like this:

Roses are red violets are blue sugar is sweet and so are you

I don't know how to display it exactly like it is in the text file (with the newlines after each statement. I know you can just do while(nextCharacter != newLn) for reading in by chars but strings got me stumped.

Answer 1

When you use formatted extraction functions, such as:

while(ins >> aString){

you lose all the whitespace characters that are present in the stream.

In order to preserve the whitespaces, you can use std::getline .

std::string line;
while ( getline(ins, line) )
{
   std::cout << line << std::endl; 
}

If you need to extract the individual tokens from the lines, you can process the lines of text using std::istringstream .

std::string line;
while ( getline(ins, line) )
{
   cout << line << std::endl; 
   std::istringstream str(line);
   std::string token;
   while ( str >> token )
   {
      // Use token
   }
}

Answer 2

You are using the "fstream extraction operator" to read in the file content. So keep in mind the operator doesn't read take in account white spaces and new lines but it consider them to be the end of the word. So instead use std::getline .

while(std::getline(ins, aString) )
    std::cout << aString << std::endl;