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Coding Style

Bash and Shell

When refactoring, writing or altering scripts, that is Shell and bash scripts, in any way, adhere to these rules:

  1. Adjust your style of coding to the style that is already present! Even if you do not like it, this is due to consistency. There was a lot of work involved in making all scripts consistent.
  2. Use shellcheck to check your scripts! Your contributions are checked by GitHub Actions too, so you will need to do this. You can lint your work with make lint to check against all targets.
  3. Use the provided .editorconfig file.
  4. Use /bin/bash instead of /bin/sh. Adjust the style accordingly.
  5. setup.sh provides a good starting point to look for.
  6. When appropriate, use the set builtin. We recommend set -euEo pipefail or set -uE.

Styling rules

If-Else-Statements

# when using braces, use double braces
# remember you do not need "" when using [[ ]]
if [[ <CONDITION1> ]] && [[ -f ${FILE} ]]
then
  <CODE TO RUN>
# when running commands, you don't need braces
elif <COMMAND TO RUN>
  <CODE TO TUN>
else
  <CODE TO TUN>
fi

# equality checks with numbers are done
# with -eq/-ne/-lt/-ge, not != or ==
if [[ ${VAR} -ne 42 ]] || [[ ${SOME_VAR} -eq 6 ]]
then
  <CODE TO RUN>
fi

Variables & Braces

Attention

Variables are always uppercase. We always use braces.

If you forgot this and want to change it later, you can use this link. The used regex is \$([^{("\\'\/])([a-zA-Z0-9_]*)([^}\/ \t'"\n.\]:(=\\-]*), where you should in practice be able to replace all variable occurrences without braces with occurrences with braces.

# good
local VAR="good"
local NEW="${VAR}"

# bad -> CI will fail
var="bad"
new=$var

Loops

Like if-else, loops look like this

for / while <LOOP CONDITION>
do
  <CODE TO RUN>
done

Functions

It's always nice to see the use of functions as it also provides a clear structure. If scripts are small, this is unnecessary, but if they become larger, please consider using functions. When doing so, provide function _main.

function _<name_underscored_and_lowercase>
{
  <CODE TO RUN>

  # variables that can be local should be local
  local <LOCAL_VARIABLE_NAME>
}

Error Tracing

A construct to trace error in your scripts looks like this. Remember: Remove set -x in the end. This is for debugging purposes only.

set -xeuEo pipefail
trap '__log_err ${FUNCNAME[0]:-"?"} ${BASH_COMMAND:-"?"} ${LINENO:-"?"} ${?:-"?"}' ERR

SCRIPT='name_of_this_script.sh'

function __log_err
{
  printf "\n--- \e[1m\e[31mUNCHECKED ERROR\e[0m\n%s\n%s\n%s\n%s\n\n" \
    "  - script    = ${SCRIPT:-${0}}" \
    "  - function  = ${1} / ${2}" \
    "  - line      = ${3}" \
    "  - exit code = ${4}" 1>&2

  <CODE TO RUN AFTERWARDS>
}

Comments, Descriptiveness & An Example

Comments should only describe non-obvious matters. Comments should start lowercase when they aren't sentences. Make the code self-descriptive by using meaningful names! Make comments not longer than approximately 80 columns, then wrap the line.

A positive example, which is taken from start-mailserver.sh, would be

function _setup_postfix_aliases
{
  _notify 'task' 'Setting up Postfix Aliases'

  : >/etc/postfix/virtual
  : >/etc/postfix/regexp

  if [[ -f /tmp/docker-mailserver/postfix-virtual.cf ]]
  then
    # fixing old virtual user file
    if grep -q ",$" /tmp/docker-mailserver/postfix-virtual.cf
    then
      sed -i -e "s/, /,/g" -e "s/,$//g" /tmp/docker-mailserver/postfix-virtual.cf
    fi

    cp -f /tmp/docker-mailserver/postfix-virtual.cf /etc/postfix/virtual

    # the `to` is important, don't delete it
    # shellcheck disable=SC2034
    while read -r FROM TO
    do
      # Setting variables for better readability
      UNAME=$(echo "${FROM}" | cut -d @ -f1)
      DOMAIN=$(echo "${FROM}" | cut -d @ -f2)

      # if they are equal it means the line looks like: "user1     other@domain.tld"
      [[ "${UNAME}" != "${DOMAIN}" ]] && echo "${DOMAIN}" >> /tmp/vhost.tmp
    done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
  else
    _notify 'inf' "Warning 'config/postfix-virtual.cf' is not provided. No mail alias/forward created."
  fi

  ...
}

YAML

When formatting YAML files, use Prettier, an opinionated formatter. There are many plugins for IDEs around.

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