What is the most elegant way to read a text file with c++?
I'd like to read whole content of a text file to a std::string
object with c++.
With Python, I can write:
text = open("text.txt", "rt").read()
It is very simple and elegant. I hate ugly stuff, so I'd like to know - what is the most elegant way to read a text file with C++? Thanks.
There are many ways, you pick which is the most elegant for you.
Reading into char*:
ifstream file ("file.txt", ios::in|ios::binary|ios::ate);
if (file.is_open())
{
file.seekg(0, ios::end);
size = file.tellg();
char *contents = new char [size];
file.seekg (0, ios::beg);
file.read (contents, size);
file.close();
//... do something with it
delete [] contents;
}
Into std::string:
std::ifstream in("file.txt");
std::string contents((std::istreambuf_iterator<char>(in)),
std::istreambuf_iterator<char>());
Into vector<char>:
std::ifstream in("file.txt");
std::vector<char> contents((std::istreambuf_iterator<char>(in)),
std::istreambuf_iterator<char>());
Into string, using stringstream:
std::ifstream in("file.txt");
std::stringstream buffer;
buffer << in.rdbuf();
std::string contents(buffer.str());
file.txt is just an example, everything works fine for binary files as well, just make sure you use ios::binary in ifstream constructor.
There's another thread on this subject.
My solutions from this thread (both one-liners):
The nice (see Milan's second solution):
string str((istreambuf_iterator<char>(ifs)), istreambuf_iterator<char>());
and the fast:
string str(static_cast<stringstream const&>(stringstream() << ifs.rdbuf()).str());