Pure BASh.
Code:
#!/bin/bash
[ ${#} -lt 2 ] && { printf "${0} <string> <file(s)>\n";exit 1; }
str="${1}"; shift; files=( "${@}" ); h=0
for ((i=0; i < ${#files[@]}; i++)); do
file="${files[${i}]}"; j=0; k=1; m=
[ ${h} -lt ${#file} ] && h=${#file} || \
[ ${h} -gt ${#file} ] && for ((l=0;l < ${h} - ${#file}; l++)); do m+=" "; done
path_to_file="${file}${m}\r"; printf "${path_to_file}"
[ -r "${file}" ] || \
{ printf "\e[1m${file}\e[0m is \e[31;1mnot readable\e[0m\n" && continue; } && \
[ -d "${file}" ] || \
while read fstr; do ((j++))
[[ "${fstr}" =~ "${str}" ]] && \
{ [ ${k} -eq 1 ] && printf "\e[1m${file}\e[0m\n" && ((k=0)) || \
printf "\t${j}: ${fstr/${str}/\e[32;1m${str}\e[0m}\n"; }
done < "${file}"
done
printf "\n"
