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Answer 1

+2 A:

std::string::find does not return a boolean value. It returns an index into the string where the substring match occurs if it is successful, else it returns std::string::npos.

So you would want to say:

    if (reader.find("ZZZ") != std::string::npos){
        cout << reader << endl;
    }

Charles Salvia 2010-10-24 10:03:54

sorry, i messup the code. I will edit my quuestion

cpp_learner 2010-10-24 10:09:44

Answer 2

A:

In general using string matching just won't work to extract values from an HTML file. A proper HTML parser would be required -- they are available for C++ as standard code.

Otherwise I'd suggest using a regex library (boost::regex until C++0x comes out). You'll be able to write better expressions to capture the part of the file you are interested in.

Reading by line probably won't work since an HTML file could be one large line. Outputing then each line you find will simply emit the entire file. Thus try the regexes and look for small sections of the code and output those. The regex library will have a "match all" command (I forgot the exact name).

edA-qa mort-ora-y 2010-10-24 10:27:37

it looks like lots of things to study if I use the boost::regex. I am just starting to learn C++, it might take some time to implement it. Is there any shorter/easier way for beginner?

cpp_learner 2010-10-24 10:31:03

the regular expression that took me weeks/months to master it =(

cpp_learner 2010-10-24 10:36:15

Well, the HTML parsers are harder to use than regex. But I can say that learning regex will be well worth your time. They come up again and again and again.

edA-qa mort-ora-y 2010-10-24 20:59:04

Answer 3

A:

The skeleton code for reading lines from a file should look like this:

if( !file.good() )
  throw "opening file failed!";

for(;;) {
  std::string line;
  std::getline(file, line);
  if( !file.good() )
    break;
  // reading succeeded, process line
}

if(!file.eof())
  // error before reaching EOF

(That funny looking loop is one that checks for the ending condition in the middle of the loop. There is not such thing in C++, so you have to use an endless loop with a break in the middle.)

However, as I said in a comment to your question, reading HTML code line-by-line isn't necessarily useful, as HTML doesn't rely on specific whitespaces.

sbi 2010-10-24 12:02:07

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