gapplication can be used to start applications that have DBusActivatable set to true in their .desktop files and can be used to send messages to already-running instances of other applications.
It is possible for applications to refer to gapplication in the Exec line of their .desktop file to maintain backwards compatibility with implementations that do not directly support DBusActivatable.
launch APPID [FILE...]
The first parameter is the application ID in the familiar "reverse DNS" style (eg: 'org.gnome.app') without the .desktop suffix.
Optionally, if additional parameters are given, they are treated as the names of files to open and may be filenames or URIs. If no files are given then the application is simply activated.
action APPID ACTION [PARAMETER]
The application ID (as above) is the first parameter. The action name follows.
Optionally, following the action name can be one parameter, in GVariant format, given as a single argument. Make sure to use sufficient quoting.
Launching an application:
gapplication launch org.example.fooview
Opening a file with an application:
gapplication launch org.example.fooview ~/file.foo
Opening many files with an application:
gapplication launch org.example.fooview ~/foos/*.foo
Invoking an action on an application:
gapplication action org.example.fooview create
Invoking an action on an application, with an action:
gapplication action org.example.fooview show-item '"item_id_828739"'
The commandline interface of gapplication was designed so that it could be used directly from the Exec line of a .desktop file.
You might want to do this to allow for backwards compatibility with implementations of the specification that do not understand how to do D-Bus activation, without having to install a separate utility program.
Consider the following example:
[Desktop Entry] Version=1.1 Type=Application Name=Foo Viewer DBusActivatable=true MimeType=image/x-foo; Exec=gapplication launch org.example.fooview %F Actions=gallery;create; [Desktop Action gallery] Name=Browse Gallery Exec=gapplication action org.example.fooview gallery [Desktop Action create] Name=Create a new Foo! Exec=gapplication action org.example.fooview create
If installing an application that supports D-Bus activation you may still want to put a file in /usr/bin so that your program can be started from a terminal.
It is possible for this file to be a shell script. The script can handle arguments such as --help and --version directly. It can also parse other command line arguments and convert them to uses of gapplication to activate the application, open files, or invoke actions.
Here is a simplified example, as may be installed in /usr/bin/fooview:
#!/bin/sh case "$1" in --help) echo "see 'man fooview' for more information" ;; --version) echo "fooview 1.2" ;; --gallery) gapplication action org.example.fooview gallery ;; --create) gapplication action org.example.fooview create ;; -*) echo "unrecognised commandline argument" exit 1 ;; *) gapplication launch org.example.fooview "$@" ;; esac