quote tr character classes

diff --git a/.mutt/sendmail-checks.d/ack-recipients b/.mutt/sendmail-checks.d/ack-recipients
index f461462b6f4812506f2b6662e04ad209896c720a..d341964f47fcc42d47056e7f89184f4076dad141 100755 (executable)
--- a/.mutt/sendmail-checks.d/ack-recipients
+++ b/.mutt/sendmail-checks.d/ack-recipients
@@ -10,7 +10,7 @@
 # addresses (no newline) instead of the addresses themselves as a measure to
 # protect privacy. You can get new lines like this:
 #
-#   printf my.new@e-mail.addre.ss | tr [[:upper:]] [[:lower:]] \
+#   printf my.new@e-mail.addre.ss | tr '[[:upper:]]' '[[:lower:]]' \
 #     | sha256sum | sed -e 's, .*,,'
 #
 # E.g. my address (see below) will become
@@ -23,14 +23,14 @@ set -eu
 
 CHECKLIST="$HOME/.mutt/ack-recipients"
 HEADER=X-Acked
-ACKED_RCPTS=$(formail -czx ${HEADER}: < $1 | tr -d ',' | tr [[:upper:]] [[:lower:]])
+ACKED_RCPTS=$(formail -czx ${HEADER}: < $1 | tr -d ',' | tr '[[:upper:]]' '[[:lower:]]')
 MAILFILE="$1"; shift
 
 ret=0
 for r in $@; do
   ack=0
   # check if this recipient is in the list of acked recipients
-  rl=$(printf $r | tr [[:upper:]] [[:lower:]])
+  rl=$(printf $r | tr '[[:upper:]]' '[[:lower:]]')
   for a in $ACKED_RCPTS; do [ $a = $rl ] && ack=1 && break; done
   rs=$(printf $rl | sha256sum)
   # now check if this unacked recipient needs to be acked