diff --git a/TODO.md b/TODO.md
index a8c1513..8996811 100644
--- a/TODO.md
+++ b/TODO.md
@@ -21,6 +21,13 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 # Completed Steps
 
+- 2026-10-19: `bin/entrypoint.sh` has each of its steps in a function, and a
+  `main` at the end calls them in order, as the shell section of the code style
+  guide asks ([#163](https://git.eeqj.de/sneak/netwatch/issues/163)). It is
+  still POSIX sh with no `set -e`, and does what it did, with the same messages
+  and exit codes. Checked by running the image with each script: a normal start,
+  bad `PORT`, `TRUSTED_PROXIES` and `DATA_DIR` values, `docker stop`, INT, and
+  nginx exiting on its own
 - 2026-10-19: while report files cannot be written, the health check answers 503
   with `"status":"error"` and the same fields, so the image's `HEALTHCHECK`
   reports the container `unhealthy`
diff --git a/bin/entrypoint.sh b/bin/entrypoint.sh
index db7c3ff..7bae9d4 100755
--- a/bin/entrypoint.sh
+++ b/bin/entrypoint.sh
@@ -13,24 +13,27 @@ set -u
 # address and start anyway, and reports a bad port without naming
 # PORT, so a value that is not a usable port stops the container here,
 # before either process starts.
-export PORT="${PORT:-8080}"
-case "$PORT" in
-    *[!0-9]*)
-        echo "entrypoint: PORT must be a port number, not '$PORT'" >&2
+check_port() {
+    export PORT="${PORT:-8080}"
+    case "$PORT" in
+        *[!0-9]*)
+            echo "entrypoint: PORT must be a port number, not '$PORT'" >&2
+            exit 1
+            ;;
+    esac
+    # The length is checked first because, for a number too big for it,
+    # the shell's test prints an error and is false, so the range checks
+    # alone would let it through.
+    if [ "${#PORT}" -gt 5 ] || [ "$PORT" -lt 1 ] || [ "$PORT" -gt 65535 ]; then
+        echo "entrypoint: PORT must be from 1 to 65535, not '$PORT'" >&2
         exit 1
-        ;;
-esac
-# The length is checked first because, for a number too big for it,
-# the shell's test prints an error and is false, so the range checks
-# alone would let it through.
-if [ "${#PORT}" -gt 5 ] || [ "$PORT" -lt 1 ] || [ "$PORT" -gt 65535 ]; then
-    echo "entrypoint: PORT must be from 1 to 65535, not '$PORT'" >&2
-    exit 1
-fi
-if [ "$PORT" -eq 8081 ]; then
-    echo "entrypoint: PORT cannot be 8081, netwatch-server listens there" >&2
-    exit 1
-fi
+    fi
+    if [ "$PORT" -eq 8081 ]; then
+        echo "entrypoint: PORT cannot be 8081, netwatch-server" \
+            "listens there" >&2
+        exit 1
+    fi
+}
 
 # TRUSTED_PROXIES names the reverse proxies in front of the container,
 # as IP addresses or CIDRs separated by commas. nginx takes the client
@@ -47,21 +50,23 @@ fi
 # TRUSTED_PROXIES. Its error, naming the CIDR, is dropped for the one
 # below, naming the entry as written. set -f keeps a * in an entry from
 # becoming a list of file names.
-TRUSTED_PROXIES="${TRUSTED_PROXIES-10.0.0.0/8,172.16.0.0/12,192.168.0.0/16}"
-set -f
-for proxy in $(printf '%s' "$TRUSTED_PROXIES" | tr ',' ' '); do
-    case "$proxy" in
-        */*) cidr="$proxy" ;;
-        *:*) cidr="$proxy/128" ;;
-        *) cidr="$proxy/32" ;;
-    esac
-    if ! netwatch-server check-cidr "$cidr" 2> /dev/null; then
-        echo "entrypoint: TRUSTED_PROXIES must be IP addresses or CIDRs" \
-            "separated by commas; '$proxy' is neither" >&2
-        exit 1
-    fi
-    echo "set_real_ip_from $cidr;"
-done > /etc/nginx/trusted-proxies.conf
+write_trusted_proxies() {
+    TRUSTED_PROXIES="${TRUSTED_PROXIES-10.0.0.0/8,172.16.0.0/12,192.168.0.0/16}"
+    set -f
+    for proxy in $(printf '%s' "$TRUSTED_PROXIES" | tr ',' ' '); do
+        case "$proxy" in
+            */*) cidr="$proxy" ;;
+            *:*) cidr="$proxy/128" ;;
+            *) cidr="$proxy/32" ;;
+        esac
+        if ! netwatch-server check-cidr "$cidr" 2> /dev/null; then
+            echo "entrypoint: TRUSTED_PROXIES must be IP addresses or CIDRs" \
+                "separated by commas; '$proxy' is neither" >&2
+            exit 1
+        fi
+        echo "set_real_ip_from $cidr;"
+    done > /etc/nginx/trusted-proxies.conf
+}
 
 # netwatch-server keeps its report files in DATA_DIR, on the /data
 # volume, which may be a host directory owned by root or by another
@@ -73,12 +78,10 @@ done > /etc/nginx/trusted-proxies.conf
 # naming DATA_DIR, unless DATA_DIR is /data or a path below it, and it
 # acts on nothing outside /data, whatever symbolic or hard links it
 # meets there.
-export DATA_DIR="${DATA_DIR:-/data/reports}"
-netwatch-server prepare-data-dir "$DATA_DIR" || exit 1
-
-# A stop signal is only noted here; the loop below acts on it.
-stop_requested=""
-trap 'stop_requested=yes' TERM INT
+prepare_data_dir() {
+    export DATA_DIR="${DATA_DIR:-/data/reports}"
+    netwatch-server prepare-data-dir "$DATA_DIR" || exit 1
+}
 
 # netwatch-server runs as the netwatch user and listens on loopback
 # only, on a port other than the public one; configs/nginx.conf proxies
@@ -87,9 +90,11 @@ trap 'stop_requested=yes' TERM INT
 # the container has. The netwatch user has no login shell, hence -s
 # /bin/sh. busybox su replaces itself with the command instead of
 # staying on as its parent, so $! is the server's own PID.
-BIND_ADDRESS=127.0.0.1 PORT=8081 TRUSTED_PROXIES=127.0.0.1/32 \
-    su -s /bin/sh netwatch -c 'exec netwatch-server' &
-backend=$!
+start_backend() {
+    BIND_ADDRESS=127.0.0.1 PORT=8081 TRUSTED_PROXIES=127.0.0.1/32 \
+        su -s /bin/sh netwatch -c 'exec netwatch-server' &
+    backend=$!
+}
 
 # nginx starts through the nginx image's own entrypoint, which applies
 # the image's start-up configuration and then replaces itself with
@@ -98,9 +103,11 @@ backend=$!
 # that rendering to PORT: a variable nginx itself uses, such as $uri,
 # would otherwise be replaced by an environment variable of the same
 # name.
-NGINX_ENVSUBST_FILTER='^PORT$' \
-    /docker-entrypoint.sh nginx -g 'daemon off;' &
-nginx=$!
+start_nginx() {
+    NGINX_ENVSUBST_FILTER='^PORT$' \
+        /docker-entrypoint.sh nginx -g 'daemon off;' &
+    nginx=$!
+}
 
 running() {
     kill -0 "$1" 2>/dev/null
@@ -109,26 +116,47 @@ running() {
 # POSIX sh cannot wait for whichever of two children exits first, so
 # look once a second. The shell collects a child that has exited while
 # it runs sleep, and running() is false for that child from then on.
-while [ -z "$stop_requested" ] && running "$backend" && running "$nginx"; do
-    sleep 1
-done
+wait_for_stop_or_exit() {
+    while [ -z "$stop_requested" ] && running "$backend" && running "$nginx"; do
+        sleep 1
+    done
+}
 
 # Stop both, then wait until neither is left.
-kill -TERM "$backend" "$nginx" 2>/dev/null
-while running "$backend" || running "$nginx"; do
-    sleep 1
-done
-
-wait "$backend"
-backend_status=$?
-wait "$nginx"
-nginx_status=$?
-echo "entrypoint: netwatch-server exited $backend_status," \
-    "nginx exited $nginx_status"
+stop_both() {
+    kill -TERM "$backend" "$nginx" 2>/dev/null
+    while running "$backend" || running "$nginx"; do
+        sleep 1
+    done
+}
 
 # Success is a requested stop that both processes exited cleanly from.
-if [ -n "$stop_requested" ] && [ "$backend_status" -eq 0 ] &&
-    [ "$nginx_status" -eq 0 ]; then
-    exit 0
-fi
-exit 1
+exit_with_status() {
+    wait "$backend"
+    backend_status=$?
+    wait "$nginx"
+    nginx_status=$?
+    echo "entrypoint: netwatch-server exited $backend_status," \
+        "nginx exited $nginx_status"
+    if [ -n "$stop_requested" ] && [ "$backend_status" -eq 0 ] &&
+        [ "$nginx_status" -eq 0 ]; then
+        exit 0
+    fi
+    exit 1
+}
+
+main() {
+    check_port
+    write_trusted_proxies
+    prepare_data_dir
+    # A stop signal is only noted here; wait_for_stop_or_exit acts on it.
+    stop_requested=""
+    trap 'stop_requested=yes' TERM INT
+    start_backend
+    start_nginx
+    wait_for_stop_or_exit
+    stop_both
+    exit_with_status
+}
+
+main "$@"