B4J Code Snippet B4J Linux app: log file home folder

This code is well known, to switch the system logging into the file for the Release app version:

#if B4J
Sub RedirectOutput (Dir As String, FileName As String)
   #if RELEASE
   Dim out As OutputStream = File.OpenOutput(Dir, FileName, False) 'Set to True to append the logs
   Dim ps As JavaObject
   ps.InitializeNewInstance("java.io.PrintStream", Array(out, True, "utf8"))
   Dim jo As JavaObject
   jo.InitializeStatic("java.lang.System")
   jo.RunMethod("setOut", Array(ps))
   jo.RunMethod("setErr", Array(ps))
   #end if
End Sub
#end if

But for Linux it needs to make extra app's folder in user's home folder, to avoid messing B4J app files to be stored separately for each app:

#PackagerProperty: VMArgs = -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8 -Djdk.gtk.version=2

#if LinuxDebugging or LinuxProduction
    #VirtualMachineArgs: -Djdk.gtk.version=2 --add-opens javafx.controls/com.sun.javafx.scene.control.skin=ALL-UNNAMED
#Else
    #VirtualMachineArgs: -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8
#End If

Sub Process_Globals
    Dim fx As JFX
    Dim MainForm As Form
    Dim appname As String = "MyB4Japp"
    Dim ver As String = "0.995"
    Dim xui As XUI
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    #if LinuxDebugging or LinuxProduction  'for Linux we have to create the subfolder in the user home folder
        If File.Exists(File.DirData(appname), appname) = False Then
            File.MakeDir(File.DirData(appname), appname)
        End If
        #if Release
            others.RedirectOutput(File.Combine(File.DirData(appname), appname), "logs.txt")
        #end if
    #else
        #if Release and Production
            RedirectOutput(File.DirData(appname), "logs.txt")    'Windows will store log into %system_drive%:\Users\%user_name%\AppData\Roaming\%appname% that is read- and writeable
        #end if
    #End If

Note that here extra build configurations are to be used:

And do not forget everywhere in the project (where File.DirData is needed) to refer such path for shared files:

Sub Folder As String
    Dim res As String
    #if B4J
        #if LinuxDebugging or LinuxProduction
            res = File.Combine(File.DirData(Main.appname), Main.appname)
        #else
            res = File.DirData(Main.appname)
        #End If
    #end if
    Return res
End Sub