Примеры циклов

while :
do
 if ! pgrep incrond >/dev/null
 then
    echo "$(date) Incrond is down. Starting"
    /etc/init.d/incron start
 fi
 sleep 5
done

# Выполнять до победного:
until ls ${FILE}
do
 echo -n "a"
 sleep 1
done
# Или:
while :
do
 ls ${FILE} && break
 sleep 2
done


while :
do ping -c1 host.xxxxxxx.ru
 if [ -z $? ]
 then break
 fi
done

for ((i=0; i < 255; i++))
 do nmap 10.10.$i.0/24 -p 11 2>&1|grep -v "Transport endpoint is not connected" >>test-11
done

# Ждать, пока не отпустят ${FILE}
until ! lsof ${FILE} >/dev/null
do
 echo -n "a"
 sleep 10
done