BASH oneliners
dig +short myip.opendns.com @resolver1.opendns.com
find . -printf '%s %p\n'|sort -nr|head
find . -mtime +7 -print0 | du -hc --files0-from - | tail -n 1
find . -type f -exec ls -s {} \; | sort -nr | awk 'NR==1 { $1=""; sub(/^ /, ""); print }'
grep -E -o "(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)" file.txt
find */ | sed 's!/.*!!' | uniq -c
free && sync && echo 3 > /proc/sys/vm/drop_caches && free