Bash tool to get nth line from a file

sed -n '2p' < file.txt

will print 2nd line

sed -n '2011p' < file.txt

2011th line

sed -n '10,33p' < file.txt

line 10 up to line 33

sed -n '1p;3p' < file.txt

1st and 3th line

and so on...

For adding lines with sed, you can check this:

sed: insert a line in a certain position

head and pipe with tail will be slow for a huge file. I would suggest sed like this:

sed 'NUMq;d' file

Where NUM is the number of the line you want to print; so, for example, sed '10q;d' file to print the 10th line of file.

Explanation:

NUMq will quit immediately when the line number is NUM.

d will delete the line instead of printing it; this is inhibited on the last line because the q causes the rest of the script to be skipped when quitting.

If you have NUM in a variable, you will want to use double quotes instead of single:

sed "${NUM}q;d" file