$repository = $this->getContainer()->get( 'ezpublish.api.repository' );
$contentService = $repository->getContentService();
$contentTypeService = $this$repository->getRepository()->getContentTypeService();
$fieldTypeService = $repository->getFieldTypeService();

try
{
    $content = $contentService->loadContent( 66 );
    $contentType = $contentTypeService->loadContentType( $content->contentInfo->contentTypeId );
    // iterate over the field definitions of the content type and print out each field's identifier and value
    foreach( $contentType->fieldDefinitions as $fieldDefinition )
    {
        $output->write( $fieldDefinition->identifier . ": " );
        $fieldType = $fieldTypeService->getFieldType( $fieldDefinition->fieldTypeIdentifier );
        $field = $content->getField( $fieldDefinition->identifier );

		// We use the Field's toHash() method to get readable content out of the Field
        $valueHash = $fieldType->toHash( $field->value );
        $output->writeln( $valueHash );
    }
}
catch( \eZ\Publish\API\Repository\Exceptions\NotFoundException $e )
{
    // if the id is not found
    $output->writeln( "No content with id $contentId" );
}
catch( \eZ\Publish\API\Repository\Exceptions\UnauthorizedException $e )
{
    // not allowed to read this content
    $output->writeln( "Anonymous users are not allowed to read content with id $contentId" );
}

$repository = $this->getContainer()->get( 'ezpublish.api.repository' );
$contentService = $repository->getContentService();
$contentTypeService = $this$repository->getRepository()->getContentTypeService();
$fieldTypeService = $repository->getFieldTypeService();