Delphi编写系统服务四：如何限制系统服务和桌面程序只运行一个收藏
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 如何限制系统服务和桌面程序只运行一个

在工程加入下列代码可以设置系统服务和桌面程序只运行一个。
program FleetReportSvr;

uses
  SvcMgr,
  Forms,
  SysUtils,
  Windows,
  SvrMain in 'SvrMain.pas' {FleetReportService: TService},
  AppMain in 'AppMain.pas' {FmFleetReport}；

{$R *.RES}

const
  CSMutexName = 'Global\Services_Application_Mutex';
var
  OneInstanceMutex: THandle;
  SecMem: SECURITY_ATTRIBUTES;
  aSD: SECURITY_DESCRIPTOR;
begin
  InitializeSecurityDescriptor(@aSD, SECURITY_DESCRIPTOR_REVISION);
  SetSecurityDescriptorDacl(@aSD, True, nil, False);
  SecMem.nLength := SizeOf(SECURITY_ATTRIBUTES);
  SecMem.lpSecurityDescriptor := @aSD;
  SecMem.bInheritHandle := False;
  OneInstanceMutex := CreateMutex(@SecMem, False, CSMutexName);
  if (GetLastError = ERROR_ALREADY_EXISTS)then
  begin
    DlgError('Error, Program or service already running!');
    Exit;
  end;
  if FindCmdLineSwitch('svc', True) or
    FindCmdLineSwitch('install', True) or
    FindCmdLineSwitch('uninstall', True) then
  begin
    SvcMgr.Application.Initialize;
    SvcMgr.Application.CreateForm(TSvSvrMain, SvSvrMain);
    SvcMgr.Application.Run;
  end
  else
  begin
    Forms.Application.Initialize;
    Forms.Application.CreateForm(TFmFmMain, FmMain);
    Forms.Application.Run;
  end;
end.