basic unix

sed '1d' filename

it will delete the first line of the file.

sed '$d' filename

it will delete the last line of the file.

cat filename

it will show the content of the file

cat -b filename

it will show the content of the file with line number.

cat filename|grep -v 'word'

it will ignore the line which have a word.

sed 's/apple//g' filename

it will empty the file which has a word apple.

grep -r "word" *

search a particular word in a available lines


Note: post your doubts in comment. so that I will help you