无法似乎通过ifstream逐行读取tmp文件

Question

Just like to know what I am doing wrong. I have a file (file.tmp) that has content of : c:\\users\\documents\\file\\folder\\myfile.txt. I would like to read the tmp file with this code:

    std::ifstream istream(csTempPath);
    std::string s;
    if (istream.is_open()){
            int i = 1;
            while (std::getline(istream, s))
            {
                CString cs;
                cs.Format(L"Reading: %s", s);

                OutputDebugString(cs);
                i++;
            }
            istream.close();
        }
    else{
            OutputDebugString(L"Could not read the temp file.");
    }

The output Im getting is this:

[4376] Reading: ??
[4376] Reading: ??

I expect it to get this: c:\\users\\documents\\file\\folder\\myfile.txt but for some reason I get that,I tried variety of ways but I cant seem to know whats wrong. BTW Im a beginning programmer.

Answer 1

The %s format specifier expects a const char* (or const wchar_t* , depending on your character encoding settings), yet you are passing a std::string object. You need to invoke its c_str member:

CStringA cs;
cs.Format("Reading: %s", s.c_str());

OutputDebugStringA(cs);

Or, when using Unicode character encoding (as you seem to be):

CStringW cs;
cs.Format(L"Reading: %S", s.c_str());

OutputDebugStringW(cs);

Note that the latter uses a Microsoft-specific extension, the format specifier type %S , that performs character encoding conversions between ANSI encoding and Unicode.