nl command on Linux (number lines)

The nl command in Linux (number lines) is used to number the lines of a file. The command considers special conditions for the file header and footer.

The commonly used options are:

-h sub-option: Used to format the text header. The default is not to number the header;
-b sub-option: Used to format the body of the text. The default is to number only non-empty lines;
-f sub-option: Used to format the text footer. The default is to not number the footer.

The sub-options are:

A: Number all lines;
t: Number only completed lines;
n: Do not number lines.

Example:

Assume that the arquivo.txt has the following content:

:::
Grades and Attendance Report for Software Engineering students
———————————————————————————————
Name Note Freq. Result
———————————————————————————————
::
Carlos Torres 8.5 80% Approved
José Antônio 10.0 100% Approved
Maria de Lourdes 10.0 100% Approved
Mário Cabral 9.5 100% Approved
:
———————————————————————————————

And we use the nl command:

$ nl arquivo.txt

The result will be:

<br></br>Grades and Attendance Report for Software Engineering students <br></br>———————————————————————————————————————————————————————— Result

———————————————————————————————————
1 Carlos Torres 8.5 80% Approved
2 José Antônio 10.0 100% Approved
3 Maria de Lourdes 10.0 100% Approved
4 Mário Cabral 9.5 100% Approved —
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nl command on Linux (number lines)

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