片言1

mysql:

--        
drop table if exists TABLE_NAME;

shell:

#      
[ -s $file ] 

#       
[ -z $str ] 

#   
echo 9934234 |awk '{print rshift(and($1,99),3) }';

#    ,  subshell,export    
function inner(){
local i
for((i=0;i<10;i++))
do
  # do sth;
done

for((i=0;i<10;i++))
do
  inner
done

#shell  mysql，  column  
./mysql -Ne"select 1">cc;