---
title: 'Contributing | 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` or `/usr/bin/envbash` 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

```bash
# 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][regex]. 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.

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

# bad -> TravisCI will fail
var="bad"
new=$var
```

### Loops

Like `if-else`, loops look like this

```bash
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`.

```bash
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.

```bash
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

```bash
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][prettier], an opinionated formatter. There are many plugins for IDEs around.

[semver]: https://semver.org/
[regex]: https://regex101.com/r/ikzJpF/7
[prettier]: https://prettier.io