--- bin/compton-trans.orig	2016-09-07 08:23:44 UTC
+++ bin/compton-trans
@@ -2,7 +2,7 @@
 
 #
 # compton-trans
-# transset in a bash script
+# transset in a sh script
 # Copyright (c) 2011-2012, Christopher Jeffrey
 #
 
@@ -46,7 +46,7 @@ v=
 
 # Workaround: replace '-5' with '~5' so as not to confuse getopts.
 for v in "$@"; do
-  shift && set -- "$@" "$(echo "$v" | sed 's/^-\([0-9]\+%\?\)$/~\1/')"
+  shift && set -- "$@" "$(echo "$v" | sed 's/^-\([0-9]\{1,\}%\{0,1\}\)$/~\1/')"
 done
 
 # This takes into account the fact that getopts stops on
@@ -69,7 +69,7 @@ while test $# -gt 0; do
           OPTIND=$((OPTIND + 1))
         ;;
         name=* | window=* | opacity=*)
-          v=$(echo "$OPTARG" | sed 's/^[^=]\+=//')
+          v=$(echo "$OPTARG" | sed 's/^[^=]\{1,\}=//')
         ;;
         *)
           echo "$0: illegal option $OPTARG" >& 2
@@ -92,7 +92,7 @@ while test $# -gt 0; do
       n) wprefix='-name'; window=$OPTARG ;;
       w) wprefix='-id'; window=$OPTARG ;;
       o) opacity=$OPTARG ;;
-      \?) exit 1 ;;
+      \{0,1\}) exit 1 ;;
     esac
   done
 
@@ -102,10 +102,10 @@ while test $# -gt 0; do
 done
 
 # clean up opacity. xargs == a poor man's trim.
-opacity=$(echo "$opacity" | xargs | sed 's/%//g' | sed 's/^~\([0-9]\+\)$/-\1/')
+opacity=$(echo "$opacity" | xargs | sed 's/%//g' | sed 's/^~\([0-9]\{1,\}\)$/-\1/')
 
 # Validate opacity value
-if test -z "$action" && ! echo "$opacity" | grep -q '^[+-]\?[0-9]\+$'; then
+if test -z "$action" && ! echo "$opacity" | grep -q '^[+-]\{0,1\}[0-9]\{1,\}$'; then
   echo "Invalid opacity specified: $opacity."
   exit 1
 fi
@@ -184,7 +184,7 @@ fi
 
 # Get current opacity.
 cur=$(xprop -id "$topmost" -notype _NET_WM_WINDOW_OPACITY \
-  | sed 's/^.*\b\([0-9]\+\).*$\|^.*$/\1/')
+    | sed -n 's/^\(.*^[_[:alnum:]]\)\{0,1\}\([0-9]\{1,\}\).*$/\2/p')
 test -z "$cur" && cur=0xffffffff
 cur=$((cur * 100 / 0xffffffff))