What's the difference between ${varname} and $varname in a shell scripts

Question

I have a simple question but I wonder what is the difference between ${varname} and $varname ?

I use both but I don\'t see any difference w

Answer 1

The distinction becomes important when something follows the variable:

text="House"
plural="${text}s"

Without the braces, the shell would see texts as variable name which wouldn't work.

The braces are also necessary when you use the extended syntax to specify defaults (${name-default}), display errors when undefined (${name?error}), or pattern substitution (see this article for other patterns; it's for BASH but most work for KSH as well)

> echo $name-default
-default
> echo ${name-default}
default

Related:

• Parameter Substitution in Korn-/POSIX-Shell