Linux to check whether the program exits, exit and restart

#! / bin / bash 

dir = / home / test / compare / bin 

cd $ dir /
 while  true 
do 
ps -ef | grep  " compare " | grep -v " grep " 
# $ ? The return value of the last instruction executed (display The exit status of the last command. 0 means no error, any other value indicates that there is an error) 
# $ ? Here the return value is 1 if an error occurs
 if [ " $? " -Eq 1 ]
 then 
# When the program exits, restart the program 
    . / compare
 fi 

sleep  180 

done