How to write to a config file using libconfig?

Question

I have been using libconfig++ library to read from the config files and it works great. Plus there is decent enough information about the APIs that facilitate the read operations from structured config files using c++. However, i couldn't find anything in the documentation that helps me see how to write back to the config files. Sure, there are few functions that will help us doing it using C, but nothing for C++. Does anyone have any idea or maybe can point me to some documentation. Anyways, this is the documentation for libconfig http://www.hyperrealm.com/libconfig/libconfig_manual.html

And how the C API should be different from C++, what do you think? You can wrap it in class if you really want to. — Hi-Angel
There are methods for reading and writing Config objects here: hyperrealm.com/libconfig/… — Galik

tulu tulu · Accepted Answer · 2019-10-11T19:29:35

There is a nice example in libconfig/examples/c/example3.c

Replacing C to C++ libraries shall not be complicated.

Here is the full code as was requested:

/* ----------------------------------------------------------------------------
   libconfig - A library for processing structured configuration files
   Copyright (C) 2005-2018  Mark A Lindner
   This file is part of libconfig.
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation; either version 2.1 of
   the License, or (at your option) any later version.
   This library is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.
   You should have received a copy of the GNU Library General Public
   License along with this library; if not, see
   <http://www.gnu.org/licenses/>.
   ----------------------------------------------------------------------------
*/

#include <stdio.h>
#include <stdlib.h>
#include <libconfig.h>

/* This example constructs a new configuration in memory and writes it to
 * 'newconfig.cfg'.
 */

int main(int argc, char **argv)
{
  static const char *output_file = "newconfig.cfg";
  config_t cfg;
  config_setting_t *root, *setting, *group, *array;
  int i;

  config_init(&cfg);
  root = config_root_setting(&cfg);

  /* Add some settings to the configuration. */
  group = config_setting_add(root, "address", CONFIG_TYPE_GROUP);

  setting = config_setting_add(group, "street", CONFIG_TYPE_STRING);
  config_setting_set_string(setting, "1 Woz Way");

  setting = config_setting_add(group, "city", CONFIG_TYPE_STRING);
  config_setting_set_string(setting, "San Jose");

  setting = config_setting_add(group, "state", CONFIG_TYPE_STRING);
  config_setting_set_string(setting, "CA");

  setting = config_setting_add(group, "zip", CONFIG_TYPE_INT);
  config_setting_set_int(setting, 95110);

  array = config_setting_add(root, "numbers", CONFIG_TYPE_ARRAY);

  for(i = 0; i < 10; ++i)
  {
    setting = config_setting_add(array, NULL, CONFIG_TYPE_INT);
    config_setting_set_int(setting, 10 * i);
  }

  /* Write out the new configuration. */
  if(! config_write_file(&cfg, output_file))
  {
    fprintf(stderr, "Error while writing file.\n");
    config_destroy(&cfg);
    return(EXIT_FAILURE);
  }

  fprintf(stderr, "New configuration successfully written to: %s\n",
          output_file);

  config_destroy(&cfg);
  return(EXIT_SUCCESS);
}

/* eof */

How to write to a config file using libconfig?

1 Answers