Useful Filters

Task	Command
Trim whitespace at the end of lines	sed -E 's/\s+$//' file
Wrap long lines after at most 40 characters	sed -E 's/.{1,40}( |$)/&\n/g' file
Delete empty lines	sed '/^\s*$/d' file
Delete comment lines	grep -v '^\s*#' file
Show a config without comments and blanks	grep -Ev '^\s*(#|$)' file
Remove duplicate lines, keeping the order	awk '!seen[$0]++' file
Count occurrences of each line	sort file | uniq -c | sort -rn
Extract all IPv4 addresses	grep -oE '\b([0-9]{1,3}\.){3}[0-9]{1,3}\b' file
Replace in place, with a backup	sed -i.bak 's/old/new/g' file

fold -s -w 40 file wraps at word boundaries too, without regex.