CODINGSTYLE.md

Policy for APKBUILDs

This documents defines a policy for writing APKBUILDs.

Standard selection

APKBUILDs are POSIX shell scripts as defined in POSIX.1-2017 Volume 3. Additionally, the following extensions are supported:

1. The local keyword for introducing variables local to a function is supported, it is briefly documented in the bash manual.
2. Non-POSIX parameter extensions are supported. This includes: Substring expansions (e.g. ${var:offset:length}) and Replacement expansions (e.g. ${var/pattern/string}). The bash manual contains further information on these two expansions.

NOTE: busybox ash is currently used to evaluate APKBUILDs - since it supports additional POSIX shell extensions, your APKBUILD might be evaluated correctly, even if it is not confirming to this policy document.

Shell Style Considerations

Formatting

Indention

Indent with tabs, don't use spaces. Avoid whitespaces.

Line Length

Maximum line length is 80 characters, this should be considered a recommendation and not a strict requirement which must be followed at all costs. Most notably, automatically generated parts (e.g. by abuild checksum) are except from this rule.

Compound Statements

Put ; do and ; then on the same line as the while, for or if.

Function Declarations

• Always put the function name, the parenthesis and the curly brackets on the same line.
• Don't use spacing between function name and parenthesis.
• Do use spacing between function parenthesis and curly brackets.

Case statement

• Don't indent alternatives.
• A one-line alternative needs a space after the close parenthesis of the pattern and before the ;;.
• End the last case with ;;.

Variable expansion

• Use ${var} over $var only when it is strictly necessary. Meaning: Only if the character following the variable name is an underscore or an alphanumeric character.