A series of fixes related to stuff I came across

bin/postshow.bash

@@ -52,6 +52,13 @@ then
   exit 2
 fi
 
+if [ "$( file "${shownotes_json}" | grep -ic "text" )" -eq 0 ]
+then
+  echo "ERROR: \"${shownotes_json}\" is not a text file"
+  exit 3
+fi
+
+
 jq '.' "${shownotes_json}" | sponge  "${shownotes_json}"
 
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