run-pktvisor.sh IFS fix for args with spaces (#111)

* run-pktvisor.sh IFS fix for args with spaces
* Add check for presence of semi colon for conditional IFS
* Update README.md for pktvisor-prom-write with semi colon example

Author: rlahnemann

centralized_collection/prometheus/README.md

@@ -31,6 +31,17 @@ PKTVISORD_ARGS="--prom-instance <INSTANCE> --geo-city /geo/GeoIP2-City.mmdb --ge
 --env REMOTE_URL="https://<REMOTEHOST>/api/prom/push" --env USERNAME="<USERNAME>" --env PASSWORD="<PASSWORD>" ns1labs/pktvisor-prom-write
 ```
 
+**PKTVISORD_ARGS optionally allows a semicolon delimited list of arguments to handle arguments such as bpf filters that may contain whitespace*
+
+Example with Geo enabled and bpf filter (assuming files are located in `/usr/local/geo`):
+
+```shell
+docker pull ns1labs/pktvisor-prom-write
+docker run -d --mount type=bind,source=/usr/local/geo,target=/geo --net=host --env \
+PKTVISORD_ARGS="-b; port 53; --prom-instance; <INSTANCE>; --geo-city; /geo/GeoIP2-City.mmdb; --geo-asn; /geo/GeoIP2-ISP.mmdb; <INTERFACE>" \
+--env REMOTE_URL="https://<REMOTEHOST>/api/prom/push" --env USERNAME="<USERNAME>" --env PASSWORD="<PASSWORD>" ns1labs/pktvisor-prom-write
+```
+
 There are a several pieces of information you need to substitute above:
 
 * `<INSTANCE>`: The prometheus "instance" label for all metrics, e.g. "myhost"

centralized_collection/prometheus/docker-grafana-agent/files/run-pktvisord.sh

@@ -2,4 +2,10 @@
 
 [[ "$PKTVISORD_ARGS" == "" ]] && PKTVISORD_ARGS="eth0"
 
+if [[ "$PKTVISORD_ARGS" == *';'* ]]; then
+    # allow for space after semi ('; ') for better readability and strip leading spaces in args
+    PKTVISORD_ARGS="${PKTVISORD_ARGS//; /;}"
+    IFS=$';'
+fi
+
 exec pktvisord --prometheus $PKTVISORD_ARGS