diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea1472e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+output/
diff --git a/4467-sprout-usage/grab_shielded_data.py b/4467-sprout-usage/grab_shielded_data.py
index 6df21ee..1856ff9 100644
--- a/4467-sprout-usage/grab_shielded_data.py
+++ b/4467-sprout-usage/grab_shielded_data.py
@@ -1,18 +1,29 @@
+import os
 import sys
 from slickrpc.rpc import Proxy
 import csv
 import progressbar
 
-if not (3 <= len(sys.argv) <= 5):
-    raise SystemExit(f'Usage: {sys.argv[0]} RPCUSER RPCPASSWORD [ HOST [ PORT ] ]\n\nFound: {sys.argv}')
+usage = f'Usage: {sys.argv[0]} OUTPUTDIR RPCUSER RPCPASSWORD [ HOST [ PORT ] ]\n\nFound: {sys.argv}'
+args = sys.argv[1:]
 
-user, passwd = sys.argv[1:3]
-host = '127.0.0.1'
-if len(sys.argv) > 3:
-    host = sys.argv[3]
-port = '8232'
-if len(sys.argv) > 4:
-    port = sys.argv[4]
+def pop_arg(name, default=None):
+    try:
+        return args.pop(0)
+    except IndexError:
+        if default is None:
+            raise SystemExit(f'Missing {name} argument.\n\n{usage}')
+        else:
+            return default
+
+os.chdir(pop_arg('OUTPUTDIR'))
+user = pop_arg('RPCUSER')
+passwd = pop_arg('RPCPASSWORD')
+host = pop_arg('HOST', default='127.0.0.1')
+port = pop_arg('PORT', default='8232')
+
+if len(args) > 0:
+    raise SystemExit(f'Unexpected args.\n\n{usage}')
 
 rpc_url = f'http://{user}:{passwd}@{host}:{port}/'
 print(f'RPC URL: {rpc_url!r}')
diff --git a/Dockerfile b/Dockerfile
index 940628b..2047db8 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -14,4 +14,4 @@ RUN pip3 install slick-bitcoinrpc && pip3 install progressbar2
 RUN mkdir -p /project/{src,output}
 COPY . /project/src
 
-ENTRYPOINT ["python3", "/project/src/4467-sprout-usage/grab_shielded_data.py"]
+ENTRYPOINT ["python3", "/project/src/4467-sprout-usage/grab_shielded_data.py", "/project/output"]
diff --git a/docker-run.sh b/docker-run.sh
new file mode 100755
index 0000000..66d5458
--- /dev/null
+++ b/docker-run.sh
@@ -0,0 +1,10 @@
+#!/bin/bash
+set -efuo pipefail
+
+REPODIR="$(dirname "$(readlink -f "$0")")"
+OUTDIR="${REPODIR}/output"
+
+[ -d "$OUTDIR" ] || mkdir "$OUTDIR"
+
+time docker build -t zcash-graphs "$REPODIR"
+time docker run -v "${OUTDIR}:/project/output" zcash-graphs "$@"