gclass
26th February 2012 18:53 UTC

Reading registry key
Hello,

I would like to read a registry key while installation process.
if the key exist, a plugin is already installed on machine.
if the key is missing I need NSIS to install the plugin before proceeding with main software.

would like to ask your help if the code I am using is OK and I wont have troubles on other machines (works fine on my testing machine):

ReadRegStr $0 HKCR "AppID\{AGDGD-4504-JJSK-JSIE-HDGD84747}" "instl"
        ${If} ${Errors} 
                StrCpy $instplugin yes
        ${Else}
                StrCpy $instplugin no
        ${EndIf}

MSG
27th February 2012 06:13 UTC

http://nsis.sourceforge.net/Docs/Chapter4.html#4.9.2.12

As you can see, the error flag is set in more cases than just a nonexisting string.

gclass
27th February 2012 09:00 UTC

MSG thank you for reply.
as I read, the error flag will be set if:
- the value is empty.
- the type is REG_DWORD.

according to the plugin developer, "the plugin is installed if the key is string type and verify size>0"

if I get it right, I need to check that the key is holding a string with value bigger than 0, all other options indicate the plugin is not installed, am I correct?

thx

MSG
27th February 2012 10:02 UTC

If you're asking what the developer meant, how should I know? You should ask the developer.

To make sure if a registry key contains a value, you can simply check if it returns "".

gclass
27th February 2012 10:09 UTC

:) I wasnt meant to ask you what the developer meant.
I meant to ask if the code I am using is correct in case I want to check a registry key to be string type and not empty (given I will check the value is bigger than 0)

thx

Afrow UK
27th February 2012 11:23 UTC

You should add a ClearErrors before the registry read.

Stu

gclass
27th February 2012 11:39 UTC

Thx Stu

ClearErrors
ReadRegStr $0 HKCR "AppID\{AGDGD-4504-JJSK-JSIE-HDGD84747}" "instl"
        ${If} ${Errors} 
                StrCpy $instplugin yes
        ${Else}
                StrCpy $instplugin no
        ${EndIf}

Afrow UK
27th February 2012 11:52 UTC

Actually I agree with MSG, you should be checking the value is not an empty string. The error flag won't be set if the value is an empty string (i.e. because a value is still set). It'll be set if the value is the wrong type or does not exist.

Stu