That sound right to me. The exit status of the program is set some time
after it exits (by means of a unix signal triggering a Smalltalk semaphore
which wakes up a process that updates the status in the ExternalUnixOSProcess).

For a simple command line program like this, just waiting a couple hundred
milliseconds after you evaluate the command will allow time for the program
to run and for Squeak to be informed of the outcome. So a retry loop with
200ms delay is probably fine in this case. Come to think of it, there's
an OSProcess class>>waitForCommand: that will probably do exactly what you
want in this case.

Dave


On Fri, Feb 08, 2013 at 10:17:29AM -0500, Louis LaBrunda wrote:
> Hey Dave,
> 
> Thanks for the info.  Looking at the code, I see that ExternalUnixOSProcess
> is returned from "OSProcess command:...".  It has some nice methods for
> checking if the command finished ok.
> 
> I added some code to the method that calls irsend to check if the command
> is finished and if it was successful, looping on a small delay.  If after
> awhile it has not finished successfully I try again for a few times and
> then give up.  Since I'm sure the irsend command is fine, the errors should
> just be transient of the odd timing nature and retrying should work.
> 
> Lou
> 
> >There are a couple of ways that a unix program can provide error output.
> >The exit status is a simple way to communicate either success, or one of
> >possibly several not so successful outcomes. This is useful for programs
> >that are used in shell scripts for example. The other way is for the
> >program to write error messages to its stderr output stream. This is
> >common for programs for which which a user is expected to read the error
> >messages.
> >
> >I don't see anything in the man page for irsend that explains the exit
> >status values, so it's a good bet that 0 means goodness and anything
> >else means not so good. That might not be enough information to change
> >the channel on your TV, but as you say I'd go ahead and try that first
> >and see if it is good enough.
> >
> >If you need to read the error output from the stdout stream (i.e. the
> >error messages that would normally go to the console when you run
> >the irsend program), you can do this by loading the CommandShell
> >package from SqueakMap, then do something like this:
> >
> >irsend := ProxyPipeline command: 'irsend foo bar baz'.
> >
> >irsend last processProxy ==> an ExternalUnixOSProcess with pid 4157 on /usr/bin/irsend (complete, normal termination with status 1)
> >
> >irsend errorUpToEnd ==> 'irsend: could not connect to socket
> >irsend: No such file or directory
> >'
> >
> >But I think this is more complexity than you really need for this, so
> >definitely you should first try just checking for exit status 0 and see
> >if that does what you need.
> >
> >Dave
> >
> >
> >On Thu, Feb 07, 2013 at 11:37:17AM -0500, Louis LaBrunda wrote:
> >> Hi Dave,
> >> 
> >> Last night I left the RasPi running my Squeak code to change the channels.
> >> Most worked just fine.  One of the calls to "OSProcess command:..." says it
> >> had a "... normal termination with status 1".  It didn't change the
> >> channel.  I will look through the code for what this and other status codes
> >> mean but can you tell me or point me to some docs.
> >> 
> >> I would like to test for errors and retry.  For now I think I will just
> >> test for non zero.
> >> 
> >> Lou
> >> 
> >> On Tue, 5 Feb 2013 17:22:50 -0500, "David T. Lewis" <lewis at mail.msen.com>
> >> wrote:
> >> 
> >> >On Tue, Feb 05, 2013 at 03:55:14PM -0500, Louis LaBrunda wrote:
> >> >> 
> >> >> >On Mon, Feb 04, 2013 at 02:07:12PM -0500, Louis LaBrunda wrote:
> >> >> >> Hi Guys,
> >> >> >> 
> >> >> >> I would like to call irsend (a program that is part of lirc package) from
> >> >> >> Squeak on the Raspberry Pi.  Can anyone please post some sample code.
> >> >> >> 
> >> >> >
> >> >> >I'm not familiar with it myself, but if irsend is just a simple command line
> >> >> >program then I should think that you could call it easily using OSProcess.
> >> >> >
> >> >> 
> >> >> Thanks for the reply.  OSProcess sounds like it is what I need but I can't
> >> >> find any install instructions, probably because I don't know much about
> >> >> Squeak and Linux and I'm not sure where to look.
> >> >> 
> >> >
> >> >Open a SqueakMap Package Loader:
> >> >
> >> >  world -> open... -> SqueakMap Catalog
> >> >
> >> >In the SqueakMap Package Loader, select package OSProcess. Expand that
> >> >category and you will find entries for version 4.4.11 and for "head".
> >> >Either one is fine, but I usually recommend just using the latest version,
> >> >so select "head" and install it.
> >> >
> >> >Assuming that you want to run irsend with some command line parameters,
> >> >try inspecting the following expression (but use some command parameters
> >> >that actually do something):
> >> >
> >> >  OSProcess command: 'irsend foo bar baz'
> >> >
> >> >The result will be an instance of ExternalUnixOSProcess that is a proxy
> >> >for the actual irsend program that you just executed. You can send it
> >> >#succeeded to see if the command was evaluated without error.
> >> >
> >> >I think this is sufficient for what you are trying to do, but you can also
> >> >do fancier things with external programs if you load CommandShell (also
> >> >on SqueakMap).
> >> >
> >> >For additional background see http://wiki.squeak.org/squeak/708 and
> >> >http://wiki.squeak.org/squeak/1914.
> >> >
> >> >Follow up questions welcome :)
> >> >
> >> >Dave
> >> >
> >> >
> >> -----------------------------------------------------------
> >> Louis LaBrunda
> >> Keystone Software Corp.
> >> SkypeMe callto://PhotonDemon
> >> mailto:Lou at Keystone-Software.com http://www.Keystone-Software.com
> >> 
> >
> -----------------------------------------------------------
> Louis LaBrunda
> Keystone Software Corp.
> SkypeMe callto://PhotonDemon
> mailto:Lou at Keystone-Software.com http://www.Keystone-Software.com
>