Simple calculator application of the shell

. 1 ! # / Bin / the bash
 2  the while :
 . 3  do 
. 4 Read -p " Please enter the calculation rule: " the JS
 . 5  IF [the JS the -Z $]; the then 
. 6  Exit
 . 7  the else 
. 8 # echo  " $` the JS = $ echo the JS | bc` " 
. 9  echo $ =` the JS awk the BEGIN " {} the JS Print $ " `
 10  Fi 
. 11  DONE