c++ search file for regex

Question

I want to search a file with a regex and the result should be ALL matched strings.

I have already written the regex for command line execution but I need this implemented in C++:

grep -E -o "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b" filename.txt

Can I do this with the regex_search function?

According to this example here the method takes a string as input. Do I have to open it and read it in line by line myself, or is there probably a way to give the file as parameter and just get the results as return?

EDIT I implemented the regular expression search now, but I don't get the results as expected.

void readFile(fs::path filename) {
    ifstream in(filename.string(), ios::in | ios::binary);

    if (in) {
        string content;
        in.seekg(0, ios::end);
        content.resize(in.tellg());
        in.seekg(0, ios::beg);
        in.read(&content[0], content.size());
        in.close();

        searchContent(content);
    }

}

void searchContent(string content) {
     smatch match;
     regex expr("\\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}");

     while (regex_search(content, match, expr)) {
          for (auto x : match)
               cout << x << " ";

           cout << std::endl;
           content = match.suffix().str();
     }

}

My test file has the following content:

  abc@gmail.com xxx
  xxx xx test@yahoo.com xxx
  sss a@a.to

But the output I get from the program is

   abc@gmail.com xxx 
   test@yahoo.com xxx 
   a@a.to

The last xxx should not be printed!?

You can, just do not forget to use raw string literals when declaring your regex so as not to escape metacharacters twice. — Wiktor Stribiżew, Oct 29 '15 at 21:21
The answer is yes, of course, so... I suspect you are running into problems somewhere? Otherwise you wouldn't ask! — Mr Lister, Oct 29 '15 at 21:21
Oh, then this isn't really about regexes, but about reading a file into a string... See http://stackoverflow.com/questions/2602013/read-whole-ascii-file-into-c-stdstring — Mr Lister, Oct 29 '15 at 21:45
Would that be the right way, just to read in the file into a string and then pass it to regex_search? — wasp256, Oct 29 '15 at 22:10
No. Read it line-by-line and apply the regex on each line (loosely): while (1) { readline(buf); if (regex_search(buf)) print(buf); } — Craig Estey, Oct 29 '15 at 22:16
Ok I implemented the regex_search now but I don't get the right results, updated my post — wasp256, Oct 30 '15 at 10:29
Updated the code, I read the entire file into a string and then perform the search — wasp256, Oct 30 '15 at 11:31

c++ search file for regex

0 Answers0