Grep
=====

`-i` - searches for upper && lower cased  <br>
`-v word` - searches every row without `word` <br>
`-n` - shows line number of occurence <br>
`-E` - grep on steroids || egrep <br>

`grep -i "..cen" GNU` - searches for all ..cen in GNU <br>
`grep "t[wo]o" GPL-3` - searches for too && two in GPL-3, because of [wo], which stands for ||<br>
`grep -i "[^c]en" GNU` - searches for everything '*en' but 'cen'<br>
`grep "^[[:upper:]]" GNU` - searches for all rows which statrts with uppercase letters.<br>
`grep "^[A-Z].*to$" GNU` - searches for string which starts with uppercase letter and end with "to"<br>
`grep -E "GNU|License" GNU` - searches either for 'GNU' or for 'License'<br>
`grep -E "(copy)?right" GPL-3` - searches for right or copyright<br>
`grep -E "a[^[:space:]]+" GNU` - searches for any 'a' begining row without "space"<br>
`grep -E "[AEIOUaeiou]{2}" GNU` - searches for sicuence(size: 2) of vowels<br>
`grep -E "[[:alpha:]]{8,20}" GNU` - searches for words which length is BETWEEN 8 AND 20 <br>