#!/bin/bash s='14_611646T,C 14_881226CT,C 14_861416.1GGC,GGCGCGCGCG' sed 's/\(.*[0-9]\)\([^0-9]\)/\1 \2/' <<< "$s" sed -E 's/(.*[0-9])([^0-9])/\1 \2/' <<< "$s"
Standard input is empty
14_611646 T,C 14_881226 CT,C 14_861416.1 GGC,GGCGCGCGCG 14_611646 T,C 14_881226 CT,C 14_861416.1 GGC,GGCGCGCGCG