Simple glob in C++ on unix system?

Question

I want to retrieve all the matching paths following this pattern in a vector<string>:

"/some/path/img*.png"

How can I simply do that ?

Answer 1

I have that in my gist. I created a stl wrapper around glob so that it returns vector of string and take care of freeing glob result. Not exactly very efficient but this code is a little more readable and some would say easier to use.

#include <glob.h> // glob(), globfree()
#include <string.h> // memset()
#include <vector>
#include <stdexcept>
#include <string>
#include <sstream>

std::vector<std::string> glob(const std::string& pattern) {
    using namespace std;

    // glob struct resides on the stack
    glob_t glob_result;
    memset(&glob_result, 0, sizeof(glob_result));

    // do the glob operation
    int return_value = glob(pattern.c_str(), GLOB_TILDE, NULL, &glob_result);
    if(return_value != 0) {
        globfree(&glob_result);
        stringstream ss;
        ss << "glob() failed with return_value " << return_value << endl;
        throw std::runtime_error(ss.str());
    }

    // collect all the filenames into a std::list<std::string>
    vector<string> filenames;
    for(size_t i = 0; i < glob_result.gl_pathc; ++i) {
        filenames.push_back(string(glob_result.gl_pathv[i]));
    }

    // cleanup
    globfree(&glob_result);

    // done
    return filenames;
}

Answer 2

I wrote a simple glob library for Windows & Linux (probably works on other *nixes as well) a while ago when I was bored, feel free to use it as you like.

Example usage:

#include <iostream>
#include "glob.h"

int main(int argc, char **argv) {
  glob::Glob glob(argv[1]);
  while (glob) {
    std::cout << glob.GetFileName() << std::endl;
    glob.Next();
  }
}

Answer 3

You can use the glob() POSIX library function.

Answer 4

For newer code to the C++17 standard, std::filesystem exists and it can achieve this with std::filesystem::directory_iterator and the recursive version. You will have to manually implement the pattern matching. For instance, the C++11 regex library. This will be portable to any platform with C++17 support.

std::filesystem::path folder("/some/path/");
if(!std::filesystem::is_directory(folder))
{
    throw std::runtime_error(folder.string() + " is not a folder");
}
std::vector<std::string> file_list;

for (const auto& entry : std::filesystem::directory_iterator(folder))
{
    const auto full_name = entry.path().string();

    if (entry.is_regular_file())
    {
       const auto base_name = entry.path().filename().string();
       /* Match the file, probably std::regex_match.. */
       if(match)
            file_list.push_back(full_name);
    }
}
return file_list;

A similar API is also implemented in boost for non-C++17 cases. std::string::compare() might be sufficient to find a match, including multiple calls, with len and pos arguments to match sub-strings only.

Answer 5

I've tried the solutions above on Centos6, and I found out that I needed to change:

int ret = glob(pat.c_str(), 0, globerr, &glob_result);

(where "globerr" is an error handling function)

Without the explicit 0, I got "GLOB_NOSPACE" error.