Linux/Unix:Find and Replace

head & tail

Show only top or bottom lines from a file

tail <num> filename

Show the last <num> lines from filename. 10 is the default

tail -f filename

Keep showing all files appended to the file

head -<num> filename

Show the first <num> lines from filename. 10 is the default

head -n -<num> filename

Show all except the last <num> lines from filename

tail +<num> filename

Show all lines from line <num> onwards

tail +<lineno> filename|head -<num>

show <num> lines starting at <lineno>

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.