Template:IO Restrictions
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Note All FlightGear disk I/O handled via Nasal scripting and/or fgcommands, is subject to access validation via IOrules. This includes the SGPath bindings in FlightGear 2.99+
However, unlike $FG_ROOT, $FG_HOME is generally accessible for writing, consider this example:
# come up with a path and filename in $FG_HOME, inside the Export sub folder, file name is test.xml
var filename = getprop("/sim/fg-home") ~ "/Export/test.xml";
# use the write_properties() helper in io.nas, which is a wrapper for the savexml fgcommand (see README.commands)
io.write_properties( path: filename, prop: "/sim" );
This will dump the sub branch of the /sim property tree into $FG_HOME/Export/test.xml
For additional examples, see $FG_ROOT/Nasal/io.nas
To learn more about PropertyList processing via loadxml and savexml, please see $FG_ROOT/Docs/README.commands
Internally, all read/write access is validated via an API called fgValidatePath(), for details please see $FG_SRC/Main/util.cxx