VB6 Console Apps

Author: Dave
Date: 02.14.19 - 3:04am

So most people dont think vb6 can be used to write console apps, and you would be forgiven for thinking so too, but you certainly can. In fact MS may have even been on the cusp of including it as a standard feature.

The reason I say this is because hardcore user The Trick over the vbforums message board posted an undocumented VBP section that he found that allows you to add extra linker switches to do exactly this.

[VBCompiler]
LinkSwitches=/SUBSYSTEM:CONSOLE

Before this was found you had to edit the produced binary yourself to change that PE header field. While this could be done manually through LordPE or your own PE parsing code the vb6 link.exe can also do it with the following command line:

link.exe /edit /subsystem:console [exePath]

If you didnt want to drop to a command shell all the time (and vb6 does not offer a post build command) then you could also use an IDE add-in such as my Fast build tool (Video) which offers both a compile as console mode feature as well as post build command capabilities and more.

The final option was to rename the link.exe and place your own proxy one in its place that allows you to control the linker arguments from a script per project script file. This technique allows you to do some extra cool stuff like compile in C object files along with your vb6 project. or write standard dlls in vb6. For these tasks I used a modified version of Jim White's LinkTool.

So now that we have a project compiling automatically as a console app, how do we read and write to the console? Here we can use two mechanisms. The ReadFile and WriteFile API are the native ways to do it. Surprisingly the Scripting.FileSystemObject TextStream class can also do the trick. Now in the IDE you wont have a pre made console available, but you can AllocConsole on your own to get one. The only thing you wont be able to test this way in the IDE is probably piping data in from the command line which is a more advanced topic anyway. Console colors and line input modes etc are also all available with the standard windows API.

Anyway there are still times where you want a console mode program (automated processing or small utils where you want to simply specify args on command line without all the clicks and types of a standard UI. So thought I would share some tidbits. Karl Peterson over at classic vb also has a console class to help with the API stuff.