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C++20 STL Cookbook

Rename Files with Regex and directory_iterator

Explore how to use C++20 STL filesystem features to rename files in a directory with regular expressions. Understand directory_iterator and regex_replace to automate filename changes, handle multiple replacements, and avoid duplicates.

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This is a simple utility that renames files using regular expressions. It uses directory_iterator to find the files in a directory and fs::rename() to rename them.

How to do it

In this recipe, we create a file rename utility that uses regular expressions:

  • We start by defining a few convenience aliases:

namespace fs = std::filesystem;
using dit = fs::directory_iterator;
using pat_v = vector<std::pair<regex, string>>;

The pat_v alias is a vector for use with our regular expressions.

  • We also continue to use the formatter specialization for path objects:

template<>
struct std::formatter<fs::path>: std::formatter<std::string> {
    template<typename FormatContext>
    auto format(const fs::path& p, FormatContext& ctx) {
        return format_to(ctx.out(), "{}", p.string());
    }
};

  • We have a function for applying the regular expression replacement to filename strings:

string replace_str(string s, const pat_v& replacements) {
    for(const auto& [pattern, repl] : replacements) {
        s = regex_replace(s, pattern, repl);
    }
    return s;
}
...