echo a{1..3}

##</code><code>##

a1 a2 a3

##</code><code>##

echo > a1; ls a{1..3}

##</code><code>##

ls: a2: No such file or directory
ls: a3: No such file or directory
a1

##</code><code>##

shopt -s extglob 
echo a@(1|2|3)

##</code><code>##

a1