323 words — 2 minutes read

Lotus Notes server on unix: Waiting for a shell command

LotusScript allows you to execute a OS command by using the rc = Shell( “command” ) command. The problem with this is, that Notes starts the command asynchronously and returns 33 as the return code, meaning “it’s started”.

There is no way to actually wait for the command to finish and - gasp - even get the return code from the command back.

This was the sitatuation with a client. We needed to run unix commands and react to their outcome in LotusScript.

Read on for the solution.

This code is designed to run on a Unix (Solaris in this case) environment ( /tmp etc). Feel free to change this for a Windows system.

Add this function to the agent you are working in:

Function ExecuteShellCommand( aCommand As String, timeoutSeconds As Integer )
	' executes the specified command in a shell, waits for the command to finish and 
	' returns the return code to the caller.
 	' aborts after "timeoutSeconds"
	On Error Goto ErrorHandler
	Dim cmd As String
	Dim rcFile As String
	Dim cnt As Integer
	Dim fileNum As Integer
	Dim isDone As Boolean
	Dim rc As Variant
	rcFile = "/tmp/ln-" & Cstr(Cint(Rnd(1) * 9999))
	cmd = aCommand &  |; echo $? > | & rcFile 
	Call LogEvent( "shell: " & cmd, SEVERITY_LOW, Nothing) 
	rc = Shell( cmd )
' the command has been sent, now wait for the return
	cnt = 0
	isDone = False
	While (cnt < timeoutSeconds) And (Not isDone)
		Sleep 1
		fileNum = Freefile()
		Open rcFile For Input As fileNum
		Line Input #fileNum, rc
		isDone = True
		Close #fileNum
		Kill rcFile
		cnt = cnt + 1
	ExecuteShellCommand = rc	
	Exit Function
	If Err = 101 Then
		Resume ContinueToPoll	
	End If
	Call LogError
	Resume Next
End Function

Now you can call it like this:

  rc = ExecuteShellCommand( "ls -l", 5 )
  if rc <> 0 then
     print "something went wrong, rc: " & CStr(rc)
  end if


Jens-Christian Fischer

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