Libconfig edit config value - c++

Question

I am using libconfig to read/wirte config files in my C++ game.
Right now I just have this one config file called video.cfg:
#Video config file
video:
{
fps:
{
limited = true;
value = 20;
};
};
This config file handles the video settings of the game.
I am trying to write a very basic console program that modifies this values based on user input. However I have no idea how to do this. I can't find anything in libconfig manual and nothing on Google.
So how do you edit values in Libconfig?

Answer 1

#include <libconfig.h>
int main() {
config_t cfg;
config_setting_t *vid_fps_lim = 0;
config_setting_t *vid_fps_val = 0;
config_init(&cfg);
if (config_read_file(&cfg, "myconfig") == CONFIG_TRUE) {
/* lookup the settings we want */
vid_fps_lim = config_lookup(&cfg, "video.fps.limited");
vid_fps_val = config_lookup(&cfg, "video.fps.value");
/* print the current settings */
printf("video.fps.limited = %i\n", config_setting_get_bool(vid_fps_lim));
printf("video.fps.value = %i\n", config_setting_get_int(vid_fps_val));
/* modify the settings */
config_setting_set_bool(vid_fps_lim, 1);
config_setting_set_int(vid_fps_val, 60);
/* write the modified config back */
config_write_file(&cfg, "myconfig");
}
config_destroy(&cfg);
return 0;
}
I named the file "lcex.c" and the config file "myconfig" It builds and runs on my Debian Linux machine using the following...
gcc `pkg-config --cflags libconfig` lcex.c -o lcex `pkg-config --libs libconfig`
./lcex
Open your config file after running the app and you should see that the values have been updated.
Disclaimer...error handling left out to make it easier to read. I didn't build with -Wall, etc. As with any API, read the docs and handle potential errors.

Answer 2

I came across this question while searching for a way to have libconfig write output to a string instead of a file. I see that there's no acceptable answer here, so I thought I would provide one for posterity, even though the question is over 3 years old.
#include <stdint.h>
#include <string>
#include "libconfig.h++"
int32_t
main (void) {
libconfig::Config config;
std::string file = "test.conf";
try {
config.readFile(file.c_str());
libconfig::Setting &limited = config.lookup("video.fps.limited");
libconfig::Setting &value = config.lookup("video.fps.value");
limited = false;
value = 60;
config.writeFile(file.c_str());
}
catch (...) {
// Do something reasonable with exceptions here. Do not catch (...)
}
return 0;
}
Hope that helps someone!