Talk:cpp/filesystem/is empty

check if a text file is empty

I am having trouble checking if a text file is empty.

this is what I'm thinking structure wise:

while(fin >> s[i]) {

if(//file is empty) { exit(0); }

else // do stuff

}

re :

You may use something like this

Run this code

#include <filesystem>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <string_view>

//! @return true if text file @a file_name is empty
bool process_text_file(std::string_view const file_name)
{
    std::fstream text_file{file_name.data()};

    bool is_empty {true};

    if (!text_file.is_open()) {
        std::cout << "ERROR: can't open file: " << std::quoted(file_name) << '\n';
        return is_empty;
    }

    for (std::string line; !text_file.bad() && !text_file.eof();) {
        std::getline(text_file, line);
        // process text file line by line...
        if (!line.empty()) {
            is_empty = false;
            // do stuff...
            std::cout << line << '\n';
        }
    }

    return is_empty;
}

int main() {
    std::cout << std::boolalpha;
    using std::operator""sv;

    auto test = [](std::string_view const file_name, std::string_view const text = "") {
        std::fstream file(file_name.data(), std::ios::out);
        if (!text.empty())
            file << text;
        file.close();
        std::cout << "test file: " << std::quoted(file_name) << '\n';
        const bool is_empty = process_text_file(file_name);
        std::cout << "is empty: " << is_empty << '\n';
        std::filesystem::remove(file_name); // cleanup! be careful!
    };

    test("/tmp/test0001.txt");
    test("/tmp/test0002.txt", "line1\nline2\n");
    test("/tmp/test0003.txt", "\n\nline1\n");
}

re:

Thanks It works :)!! Layan000 (talk) 06:38, 28 February 2021 (PST)