Read text file from specific line

[Yvaine]

i have a lengthy text file with more than 50 pages. However, i may only need to read the middle few lines, let say in page 20. To save time, i do not wish to read line by line. Any suggestion?

[Yvaine]

problem is i may not know which line until i perform some logic processing. let say i want to extract text with "abc" in the file but "abc" appears in the middle. And i do not want to read from beginning