Backends are typically open-programmable, which means we can define a standard for what goes on stdin, stdout and stderr to try and maximise the common code between the backends. The following section will explain the convention used on backends/conary and backends/yum. If you are unable to write scripts that conform to these specifications then just launch a PkSpawn object in the compiled helper with stdout and stderr callbacks and then try to do screenscraping in the backend. This screenscraping is least popular for obvious reasons. Backends scripts are run with arguments and data is sent to standard out and standard error asyncronously so that PackageKit can proxy this to DBUS. A method has command line arguments seporated with tabs, and data is also seporated with tabs. The following methods are mapped from the helper to comand line programs in the compile helper. Method File Search Name search-name.* Search Group search-group.* Search Details search-details.* Search File search-file.* Install Package install.* Install File install-file.* Remove Package remove.* Get Depends get-depends.* Get Requires get-requires.* Get Update Detail get-update-detail.* Get Description get-description.* Update Package update.* Update System update-system.* Get Updates get-updates.* Refresh Cache refresh-cache.* The following commands echoed to standard error will automatically make the backend-launcher do the correct action in the compiled helper. Method Data File Percentage percentage[tab]value stderr Subpercentage subpercentage[tab]value stderr NoPercentageUpdates no-percentage-updates stderr Error error[tab]enum[tab]description stderr Status status[tab]state stderr RequireRestart requirerestart[tab]type[tab]details stderr Package package_id[tab]status[tab]package_id[tab]summary stdout Description description[tab]package_id[tab]group[tab]detail[tab]url stdout UpdateDetail package_id[tab]updates[tab]obsoletes[tab]url[tab]restart[tab]update_text stdout