variable declaration

Shell Programming and Scripting
1

Hi Guys,

What does this mean actually ? Can somebody give me any explanation ?

x=${x:=1}

Thanks

2

From the (ksh) man page:

${parameter:=word}
              If  parameter is not set or is null then set it to word; the value of the parameter is then substituted.
              Positional parameters may not be assigned to in this way.

That's to say if x is empty or not defined, it's set to 1.

3

Thank Scott