Concord - C Discord API library

About

Concord is an asynchronous C99 Discord API library with minimal external dependencies, and a low-level translation of the Discord official documentation to C code.

Examples

The following are minimalistic examples, refer to examples/ for a better overview.

Slash Commands (new method)

Note: you need to replace GUILD_ID with an actual guild ID, or this example won't compile! You can use a macro to do this: #define GUILD_ID 1234567898765431

#include <string.h>
#include <concord/discord.h>

void on_ready(struct discord *client, const struct discord_ready *event) {
    struct discord_create_guild_application_command params = {
        .name = "ping",
        .description = "Ping command!"
    };
    discord_create_guild_application_command(client, event->application->id,
                                             GUILD_ID, &params, NULL);
}

void on_interaction(struct discord *client, const struct discord_interaction *event) {
    if (event->type != DISCORD_INTERACTION_APPLICATION_COMMAND)
        return; /* return if interaction isn't a slash command */

    if (strcmp(event->data->name, "ping") == 0) {
          struct discord_interaction_response params = {
                .type = DISCORD_INTERACTION_CHANNEL_MESSAGE_WITH_SOURCE,
                .data = &(struct discord_interaction_callback_data){
                      .content = "pong"
                }
          };
          discord_create_interaction_response(client, event->id,
                                              event->token, &params, NULL);
    }
}

int main(void) {
    struct discord *client = discord_init(BOT_TOKEN);
    discord_set_on_ready(client, &on_ready);
    discord_set_on_interaction_create(client, &on_interaction);
    discord_run(client);
}

Message Commands (old method)

#include <string.h>
#include <concord/discord.h>
#include <concord/log.h>

void on_ready(struct discord *client, const struct discord_ready *event) {
    log_info("Logged in as %s!", event->user->username);
}

void on_message(struct discord *client, const struct discord_message *event) {
    if (strcmp(event->content, "ping") == 0) {
        struct discord_create_message params = { .content = "pong" };
        discord_create_message(client, event->channel_id, &params, NULL);
    }
}

int main(void) {
    struct discord *client = discord_init(BOT_TOKEN);
    discord_add_intents(client, DISCORD_GATEWAY_MESSAGE_CONTENT);
    discord_set_on_ready(client, &on_ready);
    discord_set_on_message_create(client, &on_message);
    discord_run(client);
}

Supported operating systems (minimum requirements)

• GNU/Linux 4.x
• FreeBSD 12
• NetBSD 8.1
• Windows 7 (Cygwin)
• GNU/Hurd 0.9
• Mac OS X 10.9

Note: big-endian processors running certain OSes like SPARC Solaris, PowerPC AIX, System Z z/OS or Linux, or MIPS IRIX are NOT supported. There are currently a few issues that prevent some of the logic from correctly on big-endian systems. This will be fixed soon.

Build Instructions

The only dependency is curl-7.56.1 or higher. If you are compiling libcurl from source, you will need to build it with SSL support.

On Windows

• Install Cygwin
• Make sure that you installed libcurl, gcc, make, and git when you ran the Cygwin installer!
• You will want to check the Windows tutorial here!
• Mingw64 and Msys2 are currently NOT supported. Please see this for more information.
• Once installed, compile it normally like you would on UNIX/Linux/OS X/BSD.
• Note: you will likely need to include -L/usr/local/lib -I/usr/local/include on your gcc command, or in your CFLAGS variable in your Makefile for your bot.

On Linux, BSD, and Mac OS X

(note -- # means that you should be running as root)

Ubuntu and Debian

# apt update && apt install -y libcurl4-openssl-dev

Void Linux

# xbps-install -S libcurl-devel

Alpine

# apk add curl-dev

FreeBSD

$ pkg install curl

OS X

• Note: you will need to install Xcode, or at a minimum, the command-line tools with xcode-select --install.

$ brew install curl (Homebrew)
$ port install curl (MacPorts)

Arch Linux / Manjaro (Arch based)

git clone https://aur.archlinux.org/concord-git.git
cd concord-git
makepkg -Acs
pacman -U concord-git-version-any.pkg.tar.zst

Alternatively, you can use an AUR helper:

yay -S concord-git

Setting up your environment

Clone Concord into your workspace

$ git clone https://github.com/cogmasters/concord.git && cd concord

Compile Concord

$ make

Special notes for non-Linux systems

You might run into trouble with the compiler and linker not finding your Libcurl headers. You can do something like this:

$ CFLAGS=-I<some_path> LDFLAGS=-L<some_path> make

For instance, on a FreeBSD system:

$ CFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/lib make

On OS X using MacPorts:

$ CFLAGS=-I/opt/local/include LDFLAGS=-L/opt/local/lib make

On OS X using a self-compiled libcurl:

$ CFLAGS=-I/usr/local/include LDFLAGS=-L/usr/local/include make

On Windows with Cygwin, you might need to pass both arguments to use POSIX threading:

$ CFLAGS="-pthread -lpthread" make

Special note about linking Concord against another library

In some cases, you might want to link Concord into a shared object, or link it as a shared object into another shared object. In that case, you will need to compile Concord with CFLAGS="-fpic" make.

Configuring Concord

discord_config_init() is the initialization method that allows configuring your bot without recompiling.

The following outlines config.json fields:

{
  "logging": { // logging directives
    "level": "trace",        // trace, debug, info, warn, error, fatal
    "filename": "bot.log",   // the log output file
    "quiet": false,          // change to true to disable logs in console
    "overwrite": true,       // overwrite file if already exists, append otherwise
    "use_color": true,       // display color for log entries
    "http": {
      "enable": true,        // generate http specific logging
      "filename": "http.log" // the HTTP log output file
    },
    "disable_modules": ["WEBSOCKETS", "USER_AGENT"] // disable logging for these modules
  },
  "discord": { // discord directives
    "token": "YOUR-BOT-TOKEN",         // replace with your bot token
    "default_prefix": {                 
      "enable": false,                 // enable default command prefix
      "prefix": "YOUR-COMMANDS-PREFIX" // replace with your prefix
    }
  },
  ... // here you can add your custom fields *
}

* Your custom field contents can be fetched with discord_config_get_field()

Test Copycat-Bot

1. Get your bot token and add it to config.json, by assigning it to discord's "token" field. There are well written instructions from discord-irc explaining how to get your bot token and adding it to a server.
2. Build example executables:

   $ make examples

3. Run Copycat-Bot:

   $ cd examples && ./copycat

Get Copycat-Bot Response

Type a message in any channel the bot is part of and the bot should send an exact copy of it in return.

Terminate Copycat-Bot

With Ctrl+c or with Ctrl+|

Configure your build

The following outlines special flags and targets to override the default Makefile build with additional functionalities.

Special compilation flags

• -DCCORD_SIGINTCATCH
  • By default Concord will not shutdown gracefully when a SIGINT is received (i.e. Ctrl+c), enable this flag if you wish it to be handled for you.
• -DCCORD_DEBUG_WEBSOCKETS
  • Enable verbose debugging for WebSockets communication.
• -DCCORD_DEBUG_HTTP
  • Enable verbose debugging for HTTP communication.

Example:

$ CFLAGS="-DCCORD_SIGINTCATCH -DCCORD_DEBUG_HTTP" make

Special targets

• make shared
  • Produce a dynamically-linked version of Concord. This Makefile is intended for GNU-style compilers, such as gcc or clang.
• make shared_osx
  • Produce a dynamically-linked version of Concord, for OS X and Darwin systems.
• make voice
  • Enable experimental Voice Connection handling - not production ready.
• make debug
  • Enable some flags useful while developing, such as -O0 and -g

Installing Concord

(note -- # means that you should be running as root)

# make install

This will install the headers and library files into $PREFIX. You can override this as such:

# PREFIX=/opt/concord make install

Included dependencies

The following are stable and well documented dependencies that are packaged with Concord and can be included to your projects:

File	Description
cog-utils	General purpose functions aimed at portability
log.c*	A simple C99 logging library
carray*	Macro-based implementation of type-safe arrays
anomap*	Sorted key/value storage for C99
chash*	Macro-based implementation of type-safe hashtables
json-build	Tiny, zero-allocation JSON serializer
jsmn-find	Tiny, zero-allocation JSON tokenizer

* Concord uses its own modified version that may be not up to date with the original

Note that included headers must be concord/ prefixed:

#include <concord/discord.h>
#include <concord/log.h>

Standalone executable

GCC

$ gcc myBot.c -o myBot -pthread -ldiscord -lcurl

Clang

$ clang myBot.c -o myBot -pthread -ldiscord -lcurl

UNIX C compilers

This includes the following compilers:

• IBM XL C/C++ (AIX, z/OS, IBM i)
• Sun/Oracle Studio (Solaris)
• IRIX MIPSpro C++ (IRIX) -- NOTE: currently not supported
• HP aCC (HP-UX)
• Compaq C (Tru64 UNIX) -- NOTE: also currently not supported Note: if you want to actually compile this on one of the systems listed above, please see the "Compiling on old computers" guide.

$ cc myBot.c -o myBot -ldiscord -lcurl -lpthread

Note: some systems such as Cygwin require you to do this:

$ gcc myBot.c -o myBot -pthread -lpthread -ldiscord -lcurl

(this links against libpthread.a in /usr/lib)

Recommended debuggers

First, make sure your executable is compiled with the -g flag to ensure human-readable debugger messages.

Valgrind

Using valgrind to check for memory leaks:

valgrind --leak-check=full ./myBot

For a more comprehensive guide check Valgrind's Quick Start.

GDB

Using GDB to check for runtime errors, such as segmentation faults:

$ gdb ./myBot

And then execute your bot from the gdb environment:

(gdb) run

If the program has crashed, get a backtrace of the function calls leading to it:

(gdb) bt

For a more comprehensive guide check Beej's Quick Guide to GDB

Support

Problems? Check out our Discord Server

Contributing

All kinds of contributions are welcome, all we ask is to abide to our guidelines! If you want to help but is unsure where to get started then our Discord API Roadmap is a good starting point. Check our links for more helpful information.

Getting Started

• Documentation
• Discord API Roadmap

Useful links

• Migrating from V1
• Migrating from Orca