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Callisto extends Lua 5.4's standard library by adding new modules and facilities to the interpreter. It includes a file system library to manage and manipulate files and directories, a process library to find active processes and manipulate signals, and a JSON manipulation library (lua-cjson) among many more.

It is a standalone interpreter designed for people using Lua as a general scripting language, rather than using it embedded into another program, which is what Lua was designed for. Perhaps you could think of it as a replacement for Python.

First and foremost, Callisto tries to be:

• a runtime environment for Lua that includes most features people would need out of the box, all in one executable with zero dependencies
• a library that works well and integrates well with the Lua language and its standard library, and is easy to use for those who have no prior experience with C

To build Callisto, all you need is a C99 compiler. The configure script will check for the presence of various compilers before building, to decide which one to use. The compilers checked are clang, followed by gcc, followed by cc. If you have a compiler at a custom path that you would like to use over the system C compiler, just pass -c /path/to/compiler to the configure script before you build. The compiler must support gcc-like command line arguments.

Callisto has zero runtime dependencies, unless you built it with support for GNU libreadline [1]. Lua 5.4 is statically linked in. This means that the same binary will work across different Linux distributions.

Callisto relies on APIs standardized by POSIX.1-2017; therefore it cannot be used on operating systems that do not comply with this specification (like Microsoft Windows).

Theoretically Callisto should work on all operating systems implementing POSIX. It has been tested on Linux and OpenBSD; but if you find Callisto unable to build on your platform, please let me know. Send an email to [email protected] or file a ticket by emailing ~jeremy/[email protected].

[1]: libreadline support can be enabled at build time, but is disabled by default. To force building with libreadline support, pass the -wreadline flag to the configure script.

Callisto is distributed as source-only, but it's very easy to build it yourself. Just make sure you have a compiler such as gcc installed, as well as git for downloading the source code and make for compiling.

First, obtain a copy of the source code using the following command:

git clone https://git.sr.ht/~jeremy/callisto

After that, run

./configure
make

to compile Callisto and all its dependencies.

To install it, run make install as the root user in the source code directory. If you choose not to install it, you can still invoke it in the current directory.

Users of Arch Linux can install the AUR package:

https://aur.archlinux.org/packages/callisto-git

If you use Nix, you can use the flake:

nix profile install sourcehut:~jeremy/callisto

The standalone Callisto interpreter is called csto. This is the main way to run Lua programs using the Callisto libraries. Running it without arguments will start a read-eval-print loop so you can execute chunks of code interactively.

csto works just like the standalone Lua 5.4 interpreter. To execute code in a file, run csto file where file is the name of the file containing code you want to run.

Alternatively, put #!/usr/bin/env csto at the top of your script, make it executable with chmod +x, and then you can run the script as if it was a standalone executable, for example ./script.lua.

Library documentation can be found here: https://jtbx.github.io/callisto/doc

If you find a bug, please submit a report using the ticket tracker: https://todo.sr.ht/~jeremy/callisto

If you don't have a sourcehut account, you can file a ticket by sending an email to ~jeremy/[email protected].

Send patches to my public inbox using git send-email. make gitconfig will set you up with the correct settings. Preferred code style is detailed in the style.md document but is not required. Thanks :)