| Elektra 0.11.0

Plugin: validation

- infos = Information about validation plugin is in keys below
- infos/author = Markus Raab elekt.nosp@m.ra@l.nosp@m.ibele.nosp@m.ktra.nosp@m..org
- infos/licence = BSD
- infos/provides = check
- infos/needs =
- infos/placements = presetstorage
- infos/status = maintained unittest nodep libc
- infos/metadata = check/validation check/validation/message check/validation/ignorecase check/validation/match check/validation/invert check/validation/type
- infos/description = Validates key values using regular expressions

# Introduction

This plugin is a check plugin which checks string values of Keys using regular expressions.

# Usage

The validation plugin looks for two metakeys. `check/validation` gives a regular expression to check against. If it is present, `check/validation/message` may contain an optional humanly readable message that will be passed with the error information.

Important: To validate against the whole string, you have to start the regular expression with `^` and end it with `$`. Otherwise expressions that e.g. match the empty string, always return true. Alternatively, you can use `check/validation/match=LINE`.

# Configuration

Metadata can be supplied to configure the validation:

- `check/validation/match`: You can check against `LINE`, `WORD` or `ANY`
- `check/validation/ignorecase`: If you want to ignore case.
- `check/validation/invert`: If you want to invert match.

# Implementation

The implementation consists of a loop checking for every key if it has the mentioned metakey. The check itself is done by the POSIX regular expression library with the interface `regcomp`, `regexec`, `regerror` and `regfree`. The flag `REG_EXTENDED` is passed so that the regular expression will be compiled as an extended regular expression. `REG_NOSUB` gives a better performance and subexpressions cannot be used in this setup anyway.

# Exported Methods

The plugin also exports the function `ksLookupRE()` that does a lookup in a KeySet using a regular expression. It starts from the current cursor of the KeySet and stops when the first value matches. Finally, this key is returned.