C++ equivalent of fscanf() ?

Question

And please don't say it's fscanf() ;P

I'm trying to replace this line:

if ( fscanf(fp, "P%c\n", &ch) != 1 )

If I understand correctly, it tries to read in a char and store it to &ch, only if it's between a 'P' and a '\n'. Is that right? And if it succeeds, it returns 1 (the number of characters it read)?

I'm trying to come up with a C++ version. Is there any easy way to do a formatted read like that? Or do I need to use fstream, operator>>, and nested if statements?

Answer 1

Safe C++ alternative with type checks is std::stringstream.

Answer 2

In Visual Studio, the safe, but non-portable, equivalent function is fscanf_s.

In general, for portability, you would use one of the stream classes, which, as you note, can be a pain to format correctly.

Answer 3

There's no need for nested if statements, you can use just one like you have there in fscanf.

//... open it and such
{
    // Leave ch to fall off, if it's not within the range.
    char ch;
    file >> ch;
    if ('P' <= ch && 'n' >= ch) {
       // Success!
    }
}

Also, while I despise fscanf and friends, there ARE use cases for them, the format string can be surprisingly expressive. In addition, you should use fscanf_s, which I believe has extra parameters for safety. Any compiler that warns about fscanf should suggest alternatives in the warning.