FIND

1. find . -newer postgres-2021-11-17.dump
2. find . -name 'a.out' -and -atime -1 -or -name '*.dump' -and -atime +168 -delete   # accessed more than 168 h ago
3. find . -empty -exec rm -i {} \;
4. find . -not -name 'postgres-2021-11-19.dump'
5. find . -type f -executable
6. find . -type f -perm 777 -exec chmod 644 {} \;
7. find . -type f -printf "%k\t%p\n" | sort | sed -n '1p;$p'


GREP

1. grep -n -A5 -B5 '^EE' test2.txt
2. grep -i -n 'POSIX' test2.txt | cut -f1 -d:
3. grep -o -w 'WARNING' test2.txt | wc -l
4. grep -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' test2.txt



7.1 grep -E '^[0-9]+$' test2.txt
7.2 grep -E '^[0-9]{2}/[0-9]{2}/[0-9]{4}$' test2.txt
7.3 grep -E '^(([0-9]+(\.[0-9]+)?)|[0-9]+(\.[0-9]+)?e[-+][0-9]+)$' test2.txt
7.4 grep -E '^.+@.+$' test2.txt
7.5 grep -E '^https?:\/\/.+\..+(/.*)$' test2.txt