rbucmd: start ssh-agent only if there isn't one running already

bin/rbucmd.sh

@@ -32,7 +32,7 @@ while getopts cl: flag; do
 	*)	usage
 	esac
 done
-shift $((OPTIND - 1))
+shift $(($OPTIND - 1))
 if [ $# -ne 2 ] || [ -z "$1" ] || [ -z "$2" ]; then
 	usage
 fi
@@ -41,8 +41,10 @@ backup_name=$2
 
 [ -f "$host/bulist" ] || err "no bulist present in \"$h/\""
 
+if [ -z "$SSH_AUTH_SOCK" ] || [ ! -S "$SSH_AUTH_SOCK" ]; then
 	eval $(ssh-agent -s)
 	trap 'eval $(ssh-agent -ks)' EXIT INT QUIT TERM
+fi
 
 set -e