NSIS - printing to prompt during command line install - nsis

Question

I'm making installers for windows using NSIS and have a number of custom install options that the user can specify using the command line, for example:
installer.exe /IDPATH=c:\Program Files\Adobe\Adobe InDesign CS5 /S
What I want to do is show these options to the person installing. I can easily enough parse the /? or /help parameters with ${GetParameters} and ${GetOptions}, but how do I do the actual printing to the command prompt?

Answer 1

NSIS is a GUI program and does not really have the ability to write to stdout.
On XP and later you can do this with the system plugin:
System::Call 'kernel32::GetStdHandle(i -11)i.r0'
System::Call 'kernel32::AttachConsole(i -1)'
FileWrite $0 "hello"
On < XP, there is no AttachConsole and you need to call AllocConsole on those systems (Will probably open a new console window)
Edit:
You could open a new console if the parent process does not have one already with
!include LogicLib.nsh
System::Call 'kernel32::GetStdHandle(i -11)i.r0'
System::Call 'kernel32::AttachConsole(i -1)i.r1'
${If} $0 = 0
${OrIf} $1 = 0
System::Call 'kernel32::AllocConsole()'
System::Call 'kernel32::GetStdHandle(i -11)i.r0'
${EndIf}
FileWrite $0 "hello$\n"
But it does not really make any sense as far as /? handling goes, you might as well open a message box when there is no console
!include LogicLib.nsh
StrCpy $9 "USAGE: Hello world!!" ;the message
System::Call 'kernel32::GetStdHandle(i -11)i.r0' ;try to get stdout
System::Call 'kernel32::AttachConsole(i -1)i.r1' ;attach to parent console
${If} $0 <> 0
${AndIf} $1 <> 0
FileWrite $0 "$9$\n"
${Else}
MessageBox mb_iconinformation $9
${EndIf}

Answer 2

!include LogicLib.nsh
StrCpy $9 "USAGE: Hello world!!" ;the message
System::Call 'kernel32::AttachConsole(i -1)i.r0' ;attach to parent console
${If} $0 != 0
System::Call 'kernel32::GetStdHandle(i -11)i.r0' ;console attached -- get stdout
FileWrite $0 "$9$\n"
${Else}
;no console to attach -- show gui message
MessageBox mb_iconinformation $9
${EndIf}
First attach console then get std handle. Before attach handles may (often will) be invalid.