21 essential Linux test commonly used commands, every day a knock, knock three times each, monthly cycle, all can remember! !
https://www.cnblogs.com/poloyy/category/1672457.html
Display line numbers, in addition to a blank line
This is the default
nl test.txt nl -b t test.txt
Regardless of whether the blank lines, line numbers are displayed
nl -b a test.txt
The line number is displayed on the left-most
nl -n ln test.txt
The line number is displayed on the far right
nl -n rn test.txt
The line number is displayed on the far right, the left is less than the number of bits make up 0
nl -n rz test.txt
