Langbot

Creating an image

1. Install podman
2. Build an image: podman build -t langbot .

Running a language

Run podman run --rm -i langbot ./scripts/run.sh <language>. It will read source code from stdin and execute it.

Adding your own language

1. Create a directory langs/yourlang/.
2. Create a file langs/yourlang/compile.sh.
   • This file is responsible for downloading sources for, compiling and installing your programming language.
   • It will be run using the command bash -x -euo pipefail compile.sh, in a temporary working directory which is populated with the content of langs/yourlang.
   • When downloading sources, always make sure that what you're downloading won't change. E.g with git, always git checkout a particular commit.
   • Install all build artifacts to the directory that's passed in as the $DEPLOYDIR environment variable.
   • When everything is done, run touch "$DEPLOYDIR/.done" as a final sanity check.
3. Create a file langs/yourlang/run.sh.
   • run.sh is copied to the deployment directory (what was $DEPLOYDIR in compile.sh)
   • It will be run using the command bash -euo pipefail run.sh, in the deployment directory. It should read its source code from stdin, and do whatever is necessary to execute that code.
   • If everything goes okay, exit with exit code 0; if something goes wrong, exit with a non-zero exit code.
   • You can assume that only one execution happens at a time, meaning you shouldn't worry about creating random file names for the input files.
4. Add your language to the list in scripts/compile-all.sh to make it run as part of building the podman container.

In some cases, you may also need to add dependencies to the Containerfile.

A simple example language you can take inspiration from is Osyris.

langs/osyris/compile.sh is:

git clone https://github.com/mortie/osyris.git
cd osyris
git checkout 2db1f2c1746dbda2451d8cc888921a0f518aaf78

cargo build --release
cp target/release/osyris "$DEPLOYDIR"

touch "$DEPLOYDIR/.done"

And langs/osyris/run.sh is:

cat >input.os
exec ./osyris input.os

Some development tips

• During development, it might help to remove all other languages than yours from the list of languages in scripts/compile-all.sh, so that podman build -t langbot . only needs to run your language.
• Don't be afraid to re-build the container; podman caches all the steps it can, so podman build -t langbot . doesn't start from scratch every time.
• You may want to investigate the compiler interactively, which can be done with podman run --rm -it langbot.
• In fact, I find it helpful to manually run my shell commands in an interactive container and write the compile.sh script by writing down my commands there as I go.