How to get part of a filename in bash?

Question

linux

There is a directory with files named according to the pattern username_phonenumber.txt . How to get a piece of phonenumber in bash?
Thank you.

Answer 1

for i in ls dir; do
   var=${i#*_};
   echo ${var%%.txt};
done

ls -1 dir | grep -Eo '_(\w+)\.'

Answer 2

ls *_*.txt|sed 's/^.*_\(.*\)\.txt$/\1/'

Answer 3

ls | awk -F"_|.txt" '{print $2}'

Answer 4

ls -1 | cut -d "_" -f 2 | cut -d "." -f 1