Re: parameter expansion with `:` does not work

[Chet Ramey]

On 7/7/21 6:48 PM, lisa-asket@perso.be wrote:

> I have some difficulty understanding the difference between ${parameter:-word} 
> and ${parameter:=word}, and when it is appropriate to use one as opposed to the 
> other.

Dennis Williamson succinctly summarized the differences.

> ${parameter:-word}
> If parameter is unset or null, the expansion of word is substituted. 

> ${parameter:=word}
> If parameter is unset or null, the expansion of word is assigned to parameter. The value of parameter is then substituted. 

The key difference is in the first sentence of each description.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/