If statement - How to write a null statement

Shell Programming and Scripting
1

In my ksh script, if the conditions of a if statement are true, then do nothing; otherwise, execute some commands.

How do I write the "do nothing" statement in the following example?

Example:

if (( "$x"="1" && "$y"="a" && "$z"="happy" ))
then
do nothing
else
command
command
fi

Thanks.

2 
if (( "$x"="1" && "$y"="a" && "$z"="happy" ))
then
   :
else
   command
   command
fi

Another way, invert your test :

if (( "$x"!="1" || "$y"!="a" || "$z"!="happy" ))
then
   command
   command
fi

Jean-Pierre.

3 
if (( "$x"="1" && "$y"="a" && "$z"="happy" )); then
     :
else
   command
   command
fi
4

Thanks. That works.