reshebang.cc

#include <iostream>
#include <fstream>
#include <utility>
#include <regex>
#include <experimental/filesystem>

// Recursively replace shebang lines with correct interpreter paths according to regex rules

namespace fs = std::experimental::filesystem;

// Define regexes and their replacements here:

std::pair<std::regex, std::string> regexes[] = {
        { std::regex("^#!/(.*)/perl\\b"), "#!/usr/bin/perl" },
        { std::regex("^#!/(.*)/python\\b"), "#!/usr/bin/python" }
};

// Replace first line of a specified file (infile) at path (p1) with given line (line)
void replace_file(const fs::path &p1, std::ifstream &infile, std::string &line)
{
    auto p2 = p1;
    p2.replace_filename(".temp.xxx");
    std::ofstream outfile(p2);
    outfile << line << std::endl;

    // Copy remaining lines from infile to outfile:
    std::string rline;
    while (std::getline(infile, rline)) {
        outfile << rline << std::endl;
    }

    fs::rename(p2, p1);
}

void process_file(const fs::path &p1)
{
    // std::cout << "processing file: " << p1 << std::endl;
    std::ifstream infile(p1);

    std::string orig_line;
    if (std::getline(infile, orig_line)) {
        auto line = orig_line;
        for (auto &regex : regexes) {
            line = std::regex_replace(line, regex.first, regex.second);
        }

        if (line != orig_line) {
            replace_file(p1, infile, line);
        }
    }
}

void process_path(const fs::path &p1)
{
    // std::cout << "processing path: " << p1 << std::endl;
    for (auto &entry : fs::directory_iterator(p1)) {
        if (fs::is_directory(entry.path())) {
            process_path(entry.path());
        }
        else {
            process_file(entry.path());
        }
    }
}

int main(int argc, char **argv)
{
    fs::path p1 = argv[1];
    if (argc < 2 || ! fs::is_directory(p1)) {
        std::cerr << "Too few arguments / not a path" << std::endl;
        return 1;
    }

    process_path(p1);
}