How to read from an entire file with fstream?

[AceDawg45]

So, I am making an updater in my program, with the update information in a .txt file (for now, I will change it).
Anyway, I want to set a variable (such as a char or string) as the file's content. How do I do that?
My progress so far:

ifstream updateFile;
char uFileContentAsChar[];
string uFileContentAsString;
updateFile.open("UPDATER.txt");
//string or char, and how do I do that?
updateFile.close();

[Cody0023]

You can use a vector of strings.

string words;
vector<string>stream;

while(inFile)
{
inFile>>words;
stream.push_back(words);
}

[Aceix]

You can use the char. Check: http://www.cplusplus.com/doc/tutorial/files/

Aceix.

[AceDawg45]

@Cody0023:
I have never used vectors. I tried your suggestion, but how do I then print the file's content onto the console?

[Aceix]

A ranged-based for would do.

for(auto x:stream) {
 cout<<x;
}

Using Cody0023's example. This basically is C++11 compatible, and can be read as, "for each string in the vector stream, copy the value of the string to x, and display x's value."

Aceix.

[AceDawg45]

Actually, I figured it out. I used the one example in your answer, @Aceix. The one in the reference with getline(); Thanks anyway everybody

[Duthomhas]

No no no...

If you want to slurp up an entire file in a string...

std::string readfile( const std::string& filename )
{
  std::ifstream f( filename.c_str() );
  std::ostringstream ss;
  ss << f.rdbuf();
  return ss.str();
}

This should perform quite admirably. Keep in mind that it does not do anything with platform-specific line endings or locale encodings. That is, on Windows, your string will have embedded "\r\n"s for newline instead of just "\n".

http://stackoverflow.com/questions/2602013/read-whole-ascii-file-into-c-stdstring

Write it back to file easily enough:

bool writefile( const std::string& filename, const std::string& s )
{
  std::ofstream f( filename.c_str() );
  f << s << flush;
  return f.good();
}

Notice the lack of an endl or anything like that there.


If you do plan to use a vector of strings (instead of your stated single string value), then you must take care to read the lines properly, and not just 'word' by 'word', as that loses all whitespace formatting the original text had.

std::vector <std::string> readfile( const std::string& filename )
{
  std::vector <std::string> result;
  std::ifstream f( filename.c_str() );
  std::string s;
  while (std::getline( f, s ))
    result.emplace_back( s );
  return result;
}

This also performs quite admirably. It is a text-file-only operation, and the resulting vector will not have any newline information at all (as newlines are extracted by the getline() function).

You can write it back easily enough:

bool writefile( const std::string& filename, const std::vector <std::string> & v )
{
  std::ofstream f( filename.c_str() );
  for (const std::string& s : v)
    f << s << "\n";
  f << flush;
  return f.good();
}

Notice that this time we make sure to add the newlines back into the file. Due to platform and locale considerations, this may produce a different file than the original (say, if you read a *nix file and write it on Windows). The textual information will be the same, of course.

Uh, I don't think I missed anything important...

Hope this helps.

[AceDawg45]

This is what I did: Is that a bad way of doing it?

string line;
       ifstream myfile ("UPDATER.txt");
       if (myfile.is_open())
       {
          while ( getline (myfile,line) )
          {
              cout << line << '\n';
          }
            myfile.close();
       }

       else cout << "Unable to open file";

[Duthomhas]

No, that is correct. (It is the second method I suggested.)