Add groupmerge script

groupmerge.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+#
+# groupmerge.sh
+#
+# merge two /etc/groups together, avoiding id conflicts.
+# to be used within dockerfiles
+
+if [[ ! -e $1 || ! -e $2 ]]; then
+	echo "usage: $0 <groupfile1> <groupfile2>"
+	echo "Use groupfile1 as the basis and merges missing entries from groupfile2"
+fi
+
+cat $1
+echo "# merged entries:"
+cat $2 | while read grp; do
+ 	name=$(echo $grp | cut -d ':' -f 1)
+	pass=$(echo $grp | cut -d ':' -f 2)
+	dgid=$(echo $grp | cut -d ':' -f 3)
+	rest=$(echo $grp | cut -d ':' -f 4-)
+
+	line=$(cat $1 | grep -E "^$name:")
+	if [[ $line == "" ]]; then
+	  echo $name:$pass:$(($dgid + 2000)):$rest
+	fi
+done