C++: Iterating lines in a GZ file using boost::iostreams


You’ve got a gzipped file that you want to decompress using C++. You don’t want to use pipes to gzip in an external process. You don’t want to use zlib and manual buffering either.


This is an extension of the official gzip_decompressor example. It is also applicable to bzip2 files, assuming you use the correct decompressor filter.

The program takes a single command line argument (which is a gzipped file) and prints its decompressed output to stdout.

 * myzcat.cpp
 * A zcat replacement, for educational purpose.
 * Uses boost::iostream and zlib.
 * Compile like this:
 *   clang++ -o myzcat myzcat.cpp -lz -lboost_iostreams
 * This code is published as public domain.
#include <fstream>
#include <iostream>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/gzip.hpp>

int main(int argc, char** argv) {
    if(argc < 2) {
        std::cerr << "Usage: " << argv[0] << " <gzipped input file>" << std::endl;
    //Read from the first command line argument, assume it's gzipped
    std::ifstream file(argv[1], std::ios_base::in | std::ios_base::binary);
    boost::iostreams::filtering_streambuf<boost::iostreams::input> inbuf;
    //Convert streambuf to istream
    std::istream instream(&inbuf);
    //Iterate lines
    std::string line;
    while(std::getline(instream, line)) {
        std::cout << line << std::endl;