Fix #4: Choose correct sed option for extended re

The GNU and BSD versions of sed use different options for enabling
extended regular expressions. In order for scripts to work on both
systems, the flux.sh script needs to check which sed version is
installed. This commits adds a check for this. Additionally, the
the script is aborted if sed does not seem to support extended
regexps at all.

Author: cboehme

src/main/scripts/flux.sh

@@ -4,6 +4,18 @@
 # end in an unexpected location if CDPATH is not empty.
 unset CDPATH
 
+# This script uses extended regular expressions in sed. As
+# there are two ways to enable them, we need to find out what
+# the installed version of sed supports:
+if echo "" | sed -r "" > /dev/null 2>&1 ; then
+	extended_regexp="-r"
+elif echo "" | sed -E "" > /dev/null 2>&1 ; then
+	extended_regexp="-E"
+else
+	echo "Error: sed does not seem to support extended regular expressions (neither -r nor -E works)" >&2
+	exit 2
+fi
+
 if [ -z "$BASH_SOURCE" ] ; then
 	echo "Error: cannot determine script location (\$BASH_SOURCE is not set)" >&2
 	exit 2
@@ -79,7 +91,7 @@ vars_to_script=$( cat <<'EOF'
 	q
 EOF
 )
-substitute_vars_script=$( set | sed -r "$vars_to_script" )
+substitute_vars_script=$( set | sed $extended_regexp "$vars_to_script" )
 # Substitute environment variables in the java options:
 java_opts=$( echo "$java_opts" | sed "$substitute_vars_script")
 
@@ -92,7 +104,7 @@ option_pattern="[^\"' ]*(\"[^\"\\]*(\\\\.[^\"\\]*)*\"|'[^'\\]*(\\\\.[^'\\]*)*'|\
 remove_quotes="s/(^[\"'])|(([^\\])[\"'])/\3/g"
 java_opts_array=()
 while read line ; do
-	line=$( echo "$line" | sed -r "$remove_quotes" )
+	line=$( echo "$line" | sed $extended_regexp "$remove_quotes" )
 	java_opts_array+=("$line")
 done < <( echo "$java_opts" | grep -Eo "$option_pattern" )