Linux/Unix:Find and Replace

tr

tr "[:upper:]" "[:lower:]"

tr "[abc]" "[xyz]"

Transtlate, make all lowercase

replace all a's with y, all b's with y and all c's with z, works from stdin to stdout. All sort of translations can be done

tr -d <char>

Delete <char> from standard input

sed

s/pattern/newstring/

In each line replace first occurrence of pattern with newstring. /g at the end replaces all occurrences of pattern.

s/pattern/d

Delete each line matching pattern.