At this time, the only way to share data between steps is by writing to disk. Write the data to disk in one step, and read the data from disk in the next step.

.drone.yml

@@ -6,8 +6,8 @@ steps:
 - name: prereq
   image: cburki/mosquitto-clients
   commands:
-    - echo mosquitto_sub -h mqtt.ctdo.de -t "homie/$hostname/\$localip" -C 1
-    - lastknownip=$(mosquitto_sub -h mqtt.ctdo.de -t "homie/$hostname/\$localip" -C 1)
+#    - echo mosquitto_sub -h mqtt.ctdo.de -t "homie/$hostname/\$localip" -C 1
+    - mosquitto_sub -h mqtt.ctdo.de -t "homie/$hostname/\$localip" -C 1 | tr -d '\n' >/tmp/lastknownip
   environment:
     hostname:
       from_secret: hostname
@@ -18,7 +18,7 @@ steps:
     - sed -i "s/WIFIPASS/$iotpwd/" data/homie/config.json 
     - sed -i "s/HOSTNAME/$hostname/g" data/homie/config.json 
     - sed -i "s/HOSTNAME/$hostname/g" data/homie/config.json 
-    - echo $lastknownip
+    - lastknownip=$(cat /tmp/lastknownip)
     - sed -i "s/HOSTNAME/$lastknownip/g" platformio.ini
     - cat data/homie/config.json
     - cat platformio.ini