---
date: 2023-03-29
title: Finally, Templating in Bashtard!
tags:
- Bash
- Bashtard
- FreeBSD
- GNU+Linux
---

In the past year, I've written Bashtard, a simple configuration system written
in Bash to minimize the required dependencies, and to have a better system to
handle different distributions/OSs in your cluster. Especially the past two
months I've done quite a bit of work on it. I've worked out how to do reusable
playbooks, generate a usable Debian package from the Makefile, extend the
supported platforms, and more. And now, I've finally found a library to improve
templating functionality, [Bash Pure Template](https://github.com/husixu1/bpt).

When I originally started Bashtard I had looked around for nice and simple
templating solutions that I could use. Sadly, pretty much all the available
results required me to add dependencies, or couldn't really do more than what I
did using `sed` and `awk`.

For a long time, I had accepted that the kind of system that I wanted didn't
exist, and I wasn't interested in making it myself at the time. Last night,
however, I decided to just give it a quick search to see if anything had
changed, and BPT popped up somewhere in my results. Having a quick look through
the documentation made me very interested, it seemed to have all the features I
desired, while still sticking to utilities I've already accepted for Bashtard.

With one small exception, `md5sum`. This utility is not available on the FreeBSD
systems I maintain. On FreeBSD, this tool is called `md5`, and has different
options it can use. On the bright side, both `md5sum` and `md5` accept the
content to be hashed on `STDIN`, and will write the hash to `STDOUT`.
Additionally, Bashtard already contains logic to deduce what kind of system it
is running on.

And so I decided it's worth a try. There's only 5 references to `md5sum`, and
the all happen in the same function, `bpt.fingerprint`. I've added an extra
variable, `util`, and a `case...esac` to set this variable.

```bash
local util

case "${BASHTARD_PLATFORM[key]}" in
    freebsd) util=md5 ;;
    linux-*) util=md5sum ;;
    *)
        debug "bpt/fingerprint" "Falling back to md5sum for hashing"
        util=md5sum
        ;;
esac
```

After that, just replace all the `md5sum` invocations with `"$util"`. And a
quick test later, it seems to function just fine. Implementing BPT as a library
was incredibly straightforward too.

```bash
. "$BASHTARD_LIBDIR/vendor/bpt.bash"

file_template_bpt()
{
    local file

    file="$1" ; shift

    eval "$* bpt.main ge \"$file\""
}
```

The `eval` is a bit icky, but it saves me from polluting the environment
variables through various `export`s.

Another small adjustment I've made to BPT is the shebang. Upstream uses
`#!/bin/bash`, but this is incorrect on some systems, including FreeBSD. It uses
`#!/usr/bin/env bash` in the Bashtard version. Additionally, the upstream
repository uses `.sh` as the file extension, which I've updated to be `.bash` to
more accurately reflect which shell it is used with. Upstream also uses a
4-space indent, which I've left as-is for now, since indentation is more of a
personal choice, even if that choice is wrong. Finally, I added 3 `shellcheck
disable` rules to make shellcheck happy.

After some playbook testing on my own systems, I can say that BPT works pretty
well so far, and I'm very glad the author made it available as free software.
Thanks!