regular expression of numbers in ls in linux

Question

I have several files like aa_1.txt,aa_6.txt,aa_9801234123.txt,aa_90.txt I tried to use

ll aa_[0-9]+.txt

to list them and order them as aa_1.txt,aa_6.txt,,aa_90.txt,aa_9801234123.txt. But it does not work.

Answer 1

Pipe ll through egrep:

ll | egrep "aa_[0-9]+.txt"