# Basic syntax:
grep -o -E '.{0,3}string.{0,4}' your_file.txt
# Where:
# - This expression returns 3 characters before string and 4 after
# -o specifies returning only the matching text, not the entire line
# -E specifies allowing extended regular expressions (some answers
# change this to -P, but that doesn't work on macOS)
# Note, add the -m flag if you want to specify the number of matches to
# allow per line (e.g. -m 2)