function kfindcache {
	klist -A | grep -A1 'Kerberos 5 ticket cache' | grep -iB1 "principal: .*$1" | head -n 1 | cut -f 2 -d "'"
}

function kdo {
	local princ="$1"
	shift;
	local kinit_args="-l15m -r60m -F"
	local cache=`kfindcache "$princ"`
	if [ -n "$cache" ] && ! (KRB5CCNAME="$cache" klist -s "$cache"); then
		KRB5CCNAME="$cache" kdestroy
		cache=""
	fi
	if [ -z "$cache" ]; then
		local oldcache=`klist | grep 'Kerberos 5 ticket cache' | cut -f 2 -d "'"`
		kinit $kinit_args "$princ" || return 1
		cache=`kfindcache "$princ"`
		kswitch -c "$oldcache"
	fi
	echo "Running $1 with cache $cache (for principal $princ)" >&2
	KRB5CCNAME="$cache" "$@"
}

function krootssh {
	kdo ${ATHENA_USER:-$USER}}/root@ATHENA.MIT.EDU ssh -o "GSSAPIDelegateCredentials no" "$@"
}