Skip to content

Latest commit

 

History

History
55 lines (35 loc) · 3.19 KB

Json-c.md

File metadata and controls

55 lines (35 loc) · 3.19 KB

json-c

Json-c is a c library aiming to provide an object oriented like approach to using JSON objects in C. It aims to conform to RFC 7159 while being easy to use. Most of the memory management issues are handled by the library itself 'behind the scenes'.

The home page for json-c: https://github.com/json-c/json-c.

This library allows one to easily construct JSON objects in C, read and write them, output them as JSON formatted strings and parse JSON formatted strings back into the C representation of JSON objects.

Linux users may be able to install json-c using their OS's packaging system. However, doing so may not result in the most recent version of the library. Currently, that is json-c-0.15-20200726 . For use with this tutorial, it is recommended you use at least version 0.13. Not all of the sample programs will compile with earlier versions. To install from source, see the installation instructions on the json-c github page. If you do install from source and wish to use the compiled version of json-c, as opposed to a version installed by your package manager, you are going to need to adjust the compilation instructions in this tutorial to reflect the prefix the compiled json-c is installed to.

I will be using Bodhi Linux 6.0 based on Ubuntu 20.04 as my Distro in this tutorial and gcc as my compiler. Usage of another compiler will not be discussed. Note, Bodhi 6.0 is currently unreleased but planned for this fall. So to install:

sudo apt install libjson-c-dev

This installs all the development (header) files as well as the library itself (libjson-c4). As json-c is a commonly used library, the library itself is, in all likelihood, installed by default in a Linux distro (it is in Bodhi).

For reference, the version installed is 0.13.1+dfsg-7ubuntu0.3. Note, this corresponds to Version 0.13.1, released Mar 5, 2018, as is per the case for Ubuntu LTS releases. Rather dated but sufficient enough for this tutorial.

Without much explanation, as it is rather self-explanatory, let's write our first json-c program, json-version.c:

#include <stdio.h>
#include <json-c/json.h>

int
main(void)
{
   printf("Version: %s\n", json_c_version());
   printf("Version Number: %d\n", json_c_version_num());
   return 0;
}

To compile:

gcc json-version.c -ljson-c -o json-version

The above gcc command assumes json-c was installed via the package manager. If json-c was compiled from source using the default prefix, to compile json-version.c use the command below:

gcc json-version.c -L/usr/local/lib -ljson-c -o json-version

Throughout the rest of this tutorial, compilation instructions are going to be given for only the case of a standard install via the package manager.

Now run json-version to see what version of json-c you have installed. Not very exciting but it is a start.

Problem

  1. How many packages in your distro depend upon json-c? How many of these are installed by default? Installed currently?