shell scripting - using ${variable:=","}
 

In Wicked Cool Shell Scripts on page 18 toward the bottom I see:

result="${TD:=","}${remainder}${result}"

What does the ${TD:=","} do?

The variable TD is assigned elsewhere in the script (on page 19).

Thanks,

Steve

What is Wicked Cool Shell Scripts???

A book of shell scripts by Dave Taylor. Published by No Starch Press.

${TD:=","} Use the variable "TD" if it is set. If it is not set, assign it the value ",", and then use it.

For a complete list of conditional assignment statements, do 'man bash' and read the paragraph 'Parameter Expansion'.

Thanks. I've run into this and:

${variable#?}

and

${variable%pattern}

but I haven't found a place where these parsing/assignment operators are listed.

OK. There it is. Thanks.

I just wanted to say thanks for pointing out that book , it seams llike a really good shell scripting book , just what i was looking for :)