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Passing DTMF to Shell Scripts

This is one method to pass DTMF "strings" to a shell script, to be evaluated and executed accordingly.

It is basically a workaround, as it is not normally possible with the radio channel in Asterisk/app_rpt.

This method uses an alternate "autopatch" command with a different Asterisk "context", and a few other settings that would be different than the normal autopatch function. These settings make it quiet and seamless.

Existing Autopatch Command

If you have a existing autopatch command enabled, make sure the new command number is at least 2 digits, and different than your existing autopatch command.

It is recommended that you use a prefix starting with 6, and keep your commands listed together with the autopatch command in numerical order for better readability.

You may want to consider changing the standard "autopatch down" command from 62 to 60, so that you could utilize a command structure such as:

*60 - autopatch down
*61 - autopatch up
*62 - pass DTMF to script 1
*63 - pass DTMF to script 2

Configuring rpt.conf

You need to modify rpt.conf to add another autopatchup command, with a different context, such as:

62=autopatchup,context=pass2script,noct=1,farenddisconnect=1,dialtime=10000,quiet=1

The command above will take any digits after *62 and send them to extensions.conf in the [pass2script] context. Additionally, it disables the courtesy tone, "hangs up" when your script ends, sets the inter-digit dial time to 10 seconds, and does all this quietly (no patchup or patchdn telemetry).

Configuring extensions.conf

In our dialplan, we need to create the context pass2script. This is done in extensions.conf.

Example:

[pass2script]                                                       ; this context needs to be unique in the system
exten = _X.,1,Wait,1
exten = _X.,n,SayAlpha(/var/lib/asterisk/sounds/activated,${EXTEN}) ; allison says something and then speaks the dtmf string {EXTEN}
exten = _X.,n,Wait,3                                                ; pause for a chance to cancel by hitting DTMF # (hangup)
exten = _X.,n,System(/path/to/script.sh ${EXTEN})                   ; here we pass the DTMF string to shell script script.sh
exten = _X.,n,Hangup

Putting it Together

With our example here, dialing *6212345 would pass 12345 to the shell script script.sh.

The modified autopatchup command takes the DTMF string dialed, puts it in a variable, and sends it to the pass2script context in extensions.conf. From there, it becomes pure Asterisk for how you handle the variable in the dialplan. You can use all regular Asterisk dialplan functions to evaluate, reformat, or execute, based on the contents of the ${EXTEN} variable.

You will need your shell script to receive the "DTMF number string" accordingly. Help for that is available on the internet by searching for "passing variables to shell scripts". You would likely use the variable $1 in your shell script, since we are only sending one command line argument, which should contain the DTMF string.

You don't have to pass the DTMF to an external script, you could also evaluate and pass it to internal Asterisk/app_rpt functions as well, just using the dialplan.

As noted above, you could have multiple autopatch DTMF hand-offs, as long as you first provide a new unique command number for it and a new unique context for it in your dialplan.

Example:

62=autopatchup,context=pass2script,noct=1,farenddisconnect=1,dialtime=10000,quiet=1 
63=autopatchup,context=sitecontrol,noct=1,farenddisconnect=1,dialtime=10000,quiet=1

Practical uses can be site or home control via USB or network relays, radio control/digital mode control functions, web execution scripts etc., all dependent on your script/dialplan.