Spawned Backends

Methods
Common function outputs

If you do not have a C or C++ language binding, PackageKit executes helper scripts written in pretty much any language. It then watches the standard out and standard error and parses the output into compiled backend commands. This means a python library can be interfaced easily with a C backend.

Even when using helpers, a compiled backend stub is still used for two reasons:

Backends are typically open-programmable, which means we can define a standard for what goes on stdin and stdout 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 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.

It is important to flush the standard output after each output, else Linux will helpfully buffer the output into more efficient size chunks. If you do not flush, then there will be a long IPC delay. Flushing can be achived in C using fflush or in python using sys.stdout.flush().

Methods

The following methods are mapped from the helper to comand line programs in the spawn 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.*
Resolve resolve.*
Get Requires get-requires.*
Get Update Detail get-update-detail.*
Get Details get-details.*
Get Files get-files.*
Update Package update.*
Update System update-system.*
Get Updates get-updates.*
Refresh Cache refresh-cache.*
Get Repo List get-repo-list.*
Repo Enable repo-enable.*
Repo Set Data repo-set-data.*