How to verify if program is installed in system with Inno Setup Pascal Script? - inno-setup

Question

I want to verify if user has Docker installed in their system.
If it is installed proceed further otherwise display an error message.
Previously I was looking at the registry group in Windows but it's not the correct way.
I want to check if cmd gives correct output for command docker.
function GetHKLM: Integer;
begin
if IsWin64 then
Result := HKLM64
else
Result := HKLM32;
end;
function GetHKU: Integer;
begin
if IsWin64 then
Result := HKCU64
else
Result := HKCU32;
end;
function InitializeSetup: Boolean;
begin
// Opening the setup installer initially
Result := True;
//if the docker is present in the machine registry return True else checking user registry
if not RegKeyExists(GetHKLM, 'SOFTWARE\Docker Inc.') then
begin
if not RegKeyExists(GetHKU, 'Software\Docker Inc.') then
begin
// return False to prevent installation to continue
Result := False;
// Display that you need to install docker.
SuppressibleMsgBox('<Docker not found!>', mbCriticalError, MB_OK, IDOK);
end;
end;
end;
How do I do this with just cmd? Instead of checking registry.. How can I run the command line and verify the output?
for etc:
function checkdocker() :Boolean;
var
dockerfound: string;
begin
Result :=
ShellExecute(application.handle, 'docker', nil, nil, SW_MAXIMIZE)
end;
function InitializeSetup: Boolean;
begin
Result := True;
if not checkdocker then;
SuppressibleMsgBox('<Docker not found!>', mbCriticalError, MB_OK, IDOK);
else
#continue
end;

Answer 1

To answer your literal question: Just use Exec and check the result code:
function CheckDocker: Boolean;
var
ResultCode: Integer;
begin
Result :=
Exec('docker', '', '', SW_HIDE, ewWaitUntilTerminated, ResultCode) and
(ResultCode = 0);
if Result then Log('Succeeded executing docker')
else Log('Failed to execute docker');
end;
(based on How to get an output of an Exec'ed program in Inno Setup?)
Though there's more efficient way to check if docker.exe executable is in a search path. Use FileSearch. See How can I check SQLCMD.EXE if it is installed on client in Inno Setup.