#!/bin/bash
s="Lorem ipsum dolor sit amet, consectetur
adipiscing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna
aliqua."
grep -o '.\{0,3\}eiusmod.\{0,3\}' <<< "$s"
IyEvYmluL2Jhc2gKcz0iTG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyCmFkaXBpc2NpbmcgZWxpdCwgc2VkIGRvIGVpdXNtb2QgdGVtcG9yCmluY2lkaWR1bnQgdXQgbGFib3JlIGV0IGRvbG9yZSBtYWduYQphbGlxdWEuIgpncmVwIC1vICcuXHswLDNcfWVpdXNtb2QuXHswLDNcfScgPDw8ICIkcyI=