find

Find Inside File

find ./ -type f -name '*.*' -exec grep 'STRING_TO_FIND_HERE' {} \; -print

Or

grep -rnw '/path/' -e "STRING_TO_FIND_HERE"

-r = recursive
-n = show line number
-w = whole word only (you can omit this if you need partial match).

Files files changed in last 1 day

find /path -mtime -1 -ls

-1 = changed in last 24 hours
+1 = changed earlier than 24 hours. Useful to find older files.