BBC BASIC Programmers' Reference

by Michael Hicks, June 2007

The Microsoft Windows API call “CreateToolhelp32Snapshot” takes, as its name suggests, a “snapshot” of the processes (programs) running. Each process may spawn multiple “threads”. This code lists the running processes and provides various other details of the process such as the “process ID”, the number of threads and the other “modules” (dynamic link libraries) used by the process. To keep the code short, there is no error handling. For more details about “CreateToolhelp32Snapshot” see the MSDN documentation.

      _PROCESS_ALL_ACCESS = &1F0FFF
      _MAX_PATH = 512
      _MAX_MOD_NAME = 255

      DIM pe32{dwSize%, cntUsage%, th32ProcessID%, th32DefaultHeapID%, \
      \ th32ModuleID%, cntThreads%, th32ParentProcessID%, pcPriClassBase%, \
      \ dwFlags%, szExeFile&(_MAX_PATH) }

      DIM me32{dwSize%, th32ModuleID%, th32ProcessID%, GlblcntUsage%, \
      \ ProccntUsage%, modBaseAddr%, modBaseSize%, hModule%, \
      \ szModule&(_MAX_MOD_NAME), szExePath&(_MAX_PATH) }

      pe32.dwSize% = DIM(pe32{})

      SYS "CreateToolhelp32Snapshot", 2, 0 TO hProcessSnap%
      SYS "Process32First", hProcessSnap%, pe32{}

      file$ = @tmp$ + "output.txt" : REM create an output file in temp directory
      OSCLI "SPOOL """ + file$ + """"
      REPEAT
        PRINT "======================================"
        PRINT "Process Name", pe32.szExeFile&()
        PRINT "======================================"

        SYS "OpenProcess", _PROCESS_ALL_ACCESS, pe32.th32ProcessID% TO hProcess%
        SYS "GetPriorityClass", hProcess% TO dwPriorityClass%
        SYS "CloseHandle", hProcess%

        PRINT "Process ID ", pe32.th32ProcessID%
        PRINT "Thread Count", pe32.cntThreads%
        PRINT "Parent Process ID", pe32.th32ParentProcessID%
        PRINT "Priority Base", pe32.pcPriClassBase%
        PRINT "Priority Class", dwPriorityClass%

        PROCListProcessModules(pe32.th32ProcessID%)
        SYS "Process32Next", hProcessSnap%, pe32{} TO res%
        PRINT '
      UNTIL res% = 0

      SYS "CloseHandle", hProcessSnap%
      *SPOOL
      OSCLI "RUN Notepad.exe """ + file$ + """;"
      END

      DEF PROCListProcessModules(pid%)
      LOCAL hModuleSnap%, n%, res%
      SYS "CreateToolhelp32Snapshot", 8, pid% TO hModuleSnap%
      IF hModuleSnap% = -1 ENDPROC
      me32.dwSize% = DIM(me32{})
      SYS "Module32First", hModuleSnap%, me32{}
      PRINT "----------------"
      PRINT "    Modules"
      PRINT "----------------"
      PRINT "Exe Path", me32.szExePath&()

      n% = 1
      REPEAT
        PRINT STR$(n%), me32.szModule&()
        SYS "Module32Next", hModuleSnap%, me32{} TO res%
        n% += 1
      UNTIL res% = 0
      SYS "CloseHandle", hModuleSnap%
      ENDPROC