CODEWITHSUNDEEP
c++stringfilefstream
Jarek N
Jarek N

Reputation: 55

Reading from a file without skipping whitespaces

I'm trying to make a code which would change one given word from a file, and change it into another one. The program works in a way that it copies word by word, if it's normal word it just writes it into the output file, and if it's the one i need to change it writes the one i need to change to. However, I've enountered a problem. Program is not putting whitespaces where they are in the input file. I don't know the solution to this problem, and I have no idea if I can use noskipws since I wouldn't know where the file ends.

Please keep in mind I'm a complete newbie and I have no idea how things work. I don't know if the tags are visible enough, so I will mention again that I use C++

Upvotes: 0

Views: 1270

Answers (2)

laky55555
laky55555

Reputation: 37

First I would advise you not to read and write in the same file (at least not during reading) because it will make your program much more difficult to write/read.

Second if you want to read all whitespaces easiest is to read whole line with getline().

Program that you can use for modifying words from one file to another could look something like following:

void read_file()
{
    ifstream file_read;
    ofstream file_write;
    // File from which you read some text.
    file_read.open ("read.txt");
    // File in which you will save modified text.
    file_write.open ("write.txt");

    string line;
    // Word that you look for to modify.       
    string word_to_modify = "something";
    string word_new = "something_new";

    // You need to look in every line from input file. 
    // getLine() goes from beginning of the file to the end.
    while ( getline (file_read,line) ) {
        unsigned index = line.find(word_to_modify);
        // If there are one or more occurrence of target word.
        while (index < line.length()) {
            line.replace(index, word_to_modify.length(), word_new);
            index = line.find(word_to_modify, index + word_new.length());
        }

        cout << line << '\n';
        file_write << line + '\n';
    }


    file_read.close();
    file_write.close();
}

Upvotes: 0

felix
felix

Reputation: 2230

Since each reading of word is ended with either a whitespace or end of file, you could simply check whether the thing which stop your reading is end of file, or otherwise a whitespace:

if ( reached the end of file ) {
  // What I have encountered is end of file 
  // My job is done
} else {
  // What I have encountered is a whitespace
  // I need to output a whitespace and back to work
}

And the problem here is how to check the eof(end of file). Since you are using ifstream, things will be quite simple. When a ifstream reach the end of file (all the meaningful data have been read), the ifstream::eof() function will return true. Let's assume the ifstream instance that you have is called input.

if ( input.eof() == true ) {
  // What I have encountered is end of file
  // My job is done
} else {
  // What I have encountered is a whitespace
  // I need to output a whitespace and back to work
}

PS : ifstream::good() will return false when it reaches the eof or an error occurs. Checking whether input.good() == false instead can be a better choice here.

Upvotes: 1

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