Check script with shellcheck

.github/workflows/ci.yml

@@ -0,0 +1,13 @@
+name: CI
+on:
+  push:
+  pull_request:
+jobs:
+  shellcheck:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install shellcheck
+        run: brew install shellcheck
+      - name: Run shellcheck
+        run: shellcheck --color=always mailsecchk.sh

mailsecchk.sh

@@ -5,6 +5,8 @@
 # This source code is licensed under the GPLv3 license found in the
 # LICENSE file in the root directory of this source tree.
 
+# shellcheck disable=SC3043
+
 usage()
 {
     echo "Usage: $0 [OPTIONS]..."