Searching for a phrase in a text file c++

Question

I'm trying to read a text file to find how many times a phrase/sentence(/substring?) occurs. I've done a real bodge job on it currently (see code below) but as you'll see, it relies on some rather clunky if statements.

I don't have access to the files I''ll be using it on at home, so I've used a file called big.txt and search for phrases like "and the" for the time being.

Ideally, I'd like to be able to search for "this error code 1" and it return the number of times it occurs. Any ideas on how I might get my code to work that way would be incredibly useful!

int fileSearch(string errorNameOne, string errorNameTwo, string textFile) {

string output;                                  //variable that will store word from text file


ifstream inFile;                        
inFile.open(textFile);                          //open the selected text file

if (!inFile.is_open()) {
    cerr << "The file cannot be opened";
    exit(1);
}

if (inFile.is_open()) {                         //Check to make sure the file has opened correctly

    while (!inFile.eof()) {                     //While the file is NOT at the end of the file

        inFile >> output;                       //Send the data from the file to "output" as a string

        if (output == errorNameOne) {           //Check to look for first word of error code
            marker = 1;                         //If this word is present, set a marker to 1
        }

        else if (marker == 1) {                 //If the marker is set to 1,
            if (output == errorNameTwo) {       //and if the word matches the second error code...
                count++;                        //increse count
            }

            marker = 0;                         //either way, set marker to 0 again
        }
    }
}

inFile.close();                                 //Close the opened file

return count;                                   //Function returns count of error
}

Answer 1

Given that your phrase can only occur once per line and the number follows the phrase after a number of spaces you can read the file line by line and use std::string::find() to see of your phrase is somewhere in the line. That will return the position of the phrase. You can then work on checking the rest of the line immediately after the phrase to test the number for 1 or 0.

This code may not be exactly what you want (still not certain of the exact specs) but hopefully it should contain enough examples of what you can do to achieve your goal.

// pass the open file stream in to this function along with the 
// phrase you are looking for and the number to check
int count(std::istream& is, const std::string& phrase, const int value)
{
    int count = 0;

    std::string line;
    while(std::getline(is, line)) // read the stream line by line
    {
        // check if the phrase appears somewhere in the line (pos)
        std::string::size_type pos = line.find(phrase);

        if(pos != std::string::npos) // phrase found pos = position of phrase beginning
        {
            // turn the part of the line after the phrase into an input-stream
            std::istringstream iss(line.substr(pos + phrase.size()));

            // attempt to read a number and check if the number is what we want
            int v;
            if(iss >> v && v == value)
                ++count;
        }

    }
    return count;
}

int main()
{
    const std::string file = "tmp.txt";

    std::ifstream ifs(file);

    if(!ifs.is_open())
    {
        std::cerr << "ERROR: Unable to open file: " << file << '\n';
        return -1;
    }

    std::cout << "count: " << count(ifs, "Header Tangs Present", 1) << '\n';
}

Hope this helps.