move docker build into separate script

README.md

@@ -24,17 +24,21 @@ before sharing.
 
 ## Usage
 
-The following command will build the necessary docker image, then run it
-against the signal config directory you point it to, and dump the output to
-./output/table.csv:
+First build the docker container for the tool
 
-    $ ./run.sh -c ~/.config/Signal
-
-    Sending build context to Docker daemon  380.4kB
+    $ ./build.sh
+    Sending build context to Docker daemon  716.3kB
     Step 1/12 : FROM archlinux:base-20241110.0.278197
     ---> 8f94599caa7b
-    ...
+    [...]
+    Successfully built 1c3e3a1b45f5
     Successfully tagged sigint:latest
+
+The following command will run the analysis against the signal config directory
+you point it to, and dump the output to ./output/table.csv:
+
+    $ ./run.sh -c ~/.config/Signal
+
     INFO:main:writing message count table to /output/table.csv
 
 

build.sh

@@ -0,0 +1 @@
+docker build . -t sigint

run.sh

@@ -14,7 +14,6 @@ if [ -z ${SIGNAL_DIR+x} ]; then
     exit 1
 fi
 
-docker build . -t sigint
 if [ $FILTER -eq 1 ]; then
     docker run -it -v $SIGNAL_DIR:/root/.config/Signal -v ./output:/output sigint -f config/chat_list.txt
 else