I need a quick easy way to get a string from a file in standard C++. I can write my own, but just want to know if there is already a standard way, in C++.
Equivalent of this if you know Cocoa:
NSString *string = [NSString stringWithContentsOfFile:file]; We can do it but it's a long line :
#include<fstream> #include<iostream> #include<iterator> #include<string> using namespace std; int main() { // The one-liner string fileContents(istreambuf_iterator<char>(ifstream("filename.txt")), istreambuf_iterator<char>()); // Check result cout << fileContents; } Edited : use "istreambuf_iterator" instead of "istream_iterator"
Its almost possible with an istream_iterator (3 lines!)
#include <iostream> #include <fstream> #include <iterator> #include <string> #include <sstream> using namespace std; int main() { ifstream file("filename.txt"); string fileContents; copy(istreambuf_iterator<char>(file), istreambuf_iterator<char>(), back_inserter(fileContents)); } Edited - got rid of intermediate string stream, now copies straight into the string, and now using istreambuf_iterator, which ignores whitespace (thanks Martin York for your comment).
The standard C++ library doesn't provide a function to do this.
Best I can do is 5 lines:
#include <fstream> #include <vector> using namespace std; ifstream f("filename.txt"); f.seekg(0, ios::end); vector<char> buffer(f.tellg()); f.seekg(0, ios::beg); f.read(&buffer[0], buffer.size()); 
How about:
#include <fstream> #include <sstream> #include <iostream> using namespace std; int main( void ) { stringstream os(stringstream::out); os << ifstream("filename.txt").rdbuf(); string s(os.str()); cout << s << endl; } If you do it like the following (but properly wrapped up nicely unlike below), you can read in the file without worrying about a 0x1A byte in the file (for example) cutting the reading of the file short. The previously suggested methods will choke on a 0x1A (for example) in a file.
#include <iostream> #include <cstdio> #include <vector> #include <cstdlib> using namespace std; int main() { FILE* in = fopen("filename.txt", "rb"); if (in == NULL) { return EXIT_FAILURE; } if (fseek(in, 0, SEEK_END) != 0) { fclose(in); return EXIT_FAILURE; } const long filesize = ftell(in); if (filesize == -1) { fclose(in); return EXIT_FAILURE; } vector<unsigned char> buffer(filesize); if (fseek(in, 0, SEEK_SET) != 0 || fread(&buffer[0], sizeof(buffer[0]), buffer.size(), in) != buffer.size() || ferror(in) != 0) { fclose(in); return EXIT_FAILURE; } fclose(in); } But, yeh, it's not an already-implemented 1-liner though.
Edit: 0x1A wasn't a good example as ios_base::binary will cover that. However, even then C++ streams often give me trouble when reading in png files all at once with .read(). Using the C way works better. Just can't remember a good example to show why. It was probably with .read()ing a binary file in blocks in a loop instead that can be a problem with C++ streams. So, disregard this post.
std::string temp, file; std::ifstream if(filename); while(getline(if, temp)) file += temp; It's not a short or single-statement line, but it is one line and it's really not that bad.
