Thread: Reading From Text File

C++ getline() stream functions by default read upto a newline, then discard it from the stream, placing the data into a buffer. Ie, they are for doing exactly this: reading text line by line.

If you use the fstream getline() method, you have to use a c-string for a buffer, but if you use the global getline() from <string>, you can use a C++ string object, which is probably what you want because you can then use the various string and stringstream methods to do your parsing.

IMO, c-strings and cstdio functions might be a little tidier in this case, but if you are not already familiar with them you should just learn the C++ methods. They are very different syntactically.

To get past the whitespace at the beginning, find_first_not_of:

Code:

int start_pos = str.find_first_not_of(" \t");

You can then use find_first_of(" ", start_pos) to get where the first comma should go and keep going from there, maybe:

Code:

int p = str.find_first_of(" ", start_pos);
while (p != string::npos) {
      str[p] = ',';
      p = str.find_first_of(" ", p);
}

Originally Posted by strokebow

What do you think?

Since you seem to be doing this in the context of a larger program, what I'd recommend is that you write a smaller separate program that just opens a file, parses it, and outputs to the console. You've got some basic ideas, if you fool around with them eventually you will get what you want, then you can just copy paste into your larger project. This makes life a lot easier; it's actually exactly what I'm doing right now (figuring out the best way to parse a data file using a test program), esp. if you need to examine what's really going on (as opposed to what you thought would happen) at various points.

If a variable amount of whitespace between fields is an issue, put that code into a function:

Code:

int skipWS (const string &str, int pos) {
    while (str[pos] == ' ' || str[pos] == '\t') pos++;
    return pos;
}

You can use that in your (other) loop after you find_first_of(" \t"), eg:

Code:

pos = skipWS(str, str.find_first_of(" \t", pos));