Again Diamond ..

c=25;
for i in {1..25};
do temp=$c; 
while [ $temp -gt 0 ]; 
do printf " ";
temp=$(( temp - 1 )); 
done;
j=$i; 
if [ $j -eq 1 ]; 
then printf "*"; 
else v=$(( j * 2 )); 
while [ $v -gt 0 ]; 
do printf "*";
v=$(( v - 1 )); 
done; 
fi;  
c=$(( c - 1 )); 
printf "\n"; 
done;
v=1;a=25; 
while [ $a -gt 0 ]; 
do  j=$(( 25 - a ));
while [ $j -ge 0 ];
do printf " ";
j=$(( j - 1 )); 
done;  t=$(( a * 2 ));
while [ $t -gt 0 ] ;
do printf "*"; 
t=$(( t - 1)); 
done;  
a=$(( a - 1 )); 
if [ $a -eq -1 ] ;
then printf "*";
fi; 
printf "\n";
done;