What are the different options available for the nl command?

The nl Command in Linux

The nl command in Linux is used to number lines in a file. It is a powerful tool that can be used to add line numbers to the output of other commands or to files. The nl command provides several options that allow you to customize the line numbering process, making it a versatile tool for various use cases.

Options for the nl Command

Here are the different options available for the nl command:

1. Numbering Format Options:

   • -b: Specifies the type of body lines to be numbered. The available options are:
     • a: Number all lines.
     • t: Number only non-empty lines.
     • n: No line numbering.
   • -f: Specifies the type of footer lines to be numbered. The available options are the same as for -b.
   • -h: Specifies the type of header lines to be numbered. The available options are the same as for -b.
   • -n: Specifies the numbering format. The available options are:
     • ln: Left-justified, no leading zeros.
     • rn: Right-justified, no leading zeros.
     • rz: Right-justified, leading zeros.

2. Output Options:

   • -s: Specifies the separator string used between the line number and the corresponding text line. The default separator is a tab character.
   • -w: Specifies the number of characters to be used for the line number. The default is 6.

3. Miscellaneous Options:

   • -d: Specifies the delimiter used to separate the starting line number from the increment value. The default delimiter is a single space.
   • -v: Specifies the starting line number. The default is 1.
   • -i: Specifies the increment value used between line numbers. The default is 1.

Here's an example of how you can use the nl command with some of these options:

$ cat example.txt
This is line 1.
This is line 2.
This is line 3.
This is line 4.
This is line 5.

$ nl -b a -n rz -w 3 -s ": " example.txt
001: This is line 1.
002: This is line 2.
003: This is line 3.
004: This is line 4.
005: This is line 5.

In this example, the nl command is used to number all lines (-b a), with right-justified line numbers with leading zeros (-n rz), a width of 3 characters for the line numbers (-w 3), and a colon (: ) as the separator between the line number and the text (-s ": ").

Visualizing the nl Command Options

Here's a Mermaid diagram that visualizes the different options available for the nl command:

This diagram provides a visual representation of the different options available for the nl command, making it easier to understand the various configuration possibilities.