Hi,
On Tue, 25 Aug 2020, Koenraad Lelong via fpc-pascal wrote:
> I'm extending an old daemon so it writes the data to MQTT, using
> mosquitto_pub.
>
> To have a correct message (-m ...) I need to include double-quotes. But
> it seems ExecuteProcess(exec,cmdline) splits the cmdline according some
> rules if it's a single string.
> When I tried to do it in a single string :
> -h 127.0.0.1 -t solartopic -u user -P secret -i clientid -m "{\"Pac\":
> 458.00}"
> I got :
> Error: Unknown option 'Pac\":'.
> So I need to make cmdline an array. How I do that ?
> I tried :
> MQTTStr : array [0..5] of ansistring;
> ...
> MQTTStr[0]:='-h '+MQTTBroker;
> MQTTStr[1]:='-t '+MQTTTopic;
> MQTTStr[2]:='-u '+MQTTUser;
> MQTTStr[3]:='-P '+MQTTPassw;
> MQTTStr[4]:='-i '+MQTTClientID;
> MQTTStr[5]:='-m "{\"'+ChanName+'\": '+TextValue+'}"';
> ExecuteProcess(MQTTExec,MQTTStr));
> But then :
> Error: Unknown option '-h 127.0.0.1'.
> Use 'mosquitto_pub --help' to see usage.
>
> Thanks in advance
Just a guess, but I think you need to do:
MQTTStr[0]:='-h';
MQTTStr[1]:=MQTTBroker;
MQTTStr[2]:='-t';
MQTTStr[3]:=MQTTTopic;
... etc.
MQTTStr[n]:='-m';
MQTTStr[n+1]:=MQTTMessage;
Like this. It's maybe a bit counter intuitive, but you have to think from
the perspective of the other app, everything which you put into 1 string
will go into 1 "slot" of its "ParamStr(x)". And then it's maybe more
obvious how you need to split your arguments.
BTW, shameless plug, but this is a very very hacky way to talk to an MQTT
broker I think, I've made a raw C header conversion, and a Pascal-style
multithreaded OOP wrapper for libmosquitto, so you can properly integrate
MQTT communication in your Free Pascal app (tested on Linux, MacOS and
Windows):
https://github.com/chainq/mosquitto-p
I'm not sure of the complexity of what you want to do, but for anything
remotely more complex, than sending 1 message every minute or so, this
might be a better solution than trying to squeeze things through
mosquitto_pub's arguments.
Cheers,
--
Charlie
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