An explanation of the use of the NL command under Linux

The NL command in Linux is much like the cat command, but the NL command will hit the uplink, which is a less commonly used command, with the small part below to learn about this little-known NL command.

The NL command is used in a Linux system to calculate the line number of a file. NL can automatically add a line number to the output file content! The default result is a bit different from Cat-n, NL can make the line number more display design, including the number of digits and whether auto-completion 0 and so on.

1. Command format:

NL [Options] ... [File] ...

2. Command parameters:

-B: Specifies the way the line number is specified, mainly in two ways:

-B A: Indicates that the line number (similar to cat-n) is also listed, whether or not it is a blank line;

-B T: If there is a blank line, the empty line does not list the row number (default);

-N: List the method of line number representation, there are three main kinds:

-N LN: The line number is displayed at the left of the screen;

-N RN: The line number is displayed on the very right of its own field and does not add 0;

-N RZ: line number in its own field to the right of the display, and add 0;

-W: The number of digits occupied by the line number field.

-P does not restart the calculation at the logical delimiter.

3. Command function:

The NL command reads the File parameter (standard input by default), computes the line number in the input, and writes the computed line number to standard output. In the output, the NL command calculates the left line based on the flags that you specify on the command line. The input text must be written in a logical page. Each logical page has a header, a body, and a footer section (which can have an empty section). Unless you use the-P flag, the NL command re-sets the line number where each logical page begins. Row calculation flags can be set separately for header, body, and footer sections (for example, header and footer lines can be computed but text lines cannot).

4. Usage examples:

Example one: List the contents of Log2012.log with NL

Command:

NL Log2012.log

Output:

[Email protected] test]# NL Log2012.log

1 2012-01

2 2012-02

3 ======[[email protected] test]#

Description

Blank lines in the file, NL does not add line numbers

Example two: The contents of Log2012.log are listed in NL, and the line number is also added to the empty bank.

Command:

Nl-b a Log2012.log

Output:

[Email protected] test]# Nl-b a Log2012.log

1 2012-01

2 2012-02

3

4

5 ======[[email protected] test]#

Example 3: Make the line number preceded by 0, unified output format

Command:

Output:

[Email protected] test]# nl-b a-n RZ log2014.log

000001 2014-01

000002 2014-02

000003 2014-03

000004 2014-04

000005 2014-05

000006 2014-06

000007 2014-07

000008 2014-08

000009 2014-09

000010 2014-10

000011 2014-11

000012 2014-12

000013 =======

[Email protected] test]# nl-b a-n rz-w 3 Log2014.log

001 2014-01

002 2014-02

003 2014-03

004 2014-04

005 2014-05

006 2014-06

007 2014-07

008 2014-08

009 2014-09

010 2014-10

011 2014-11

012 2014-12

013 =======

Description

Nl-b a-n RZ the command line number defaults to six bits, and the number of bits to adjust can be adjusted to 3 bits with the parameter-W 3.

Above is the Linux under the NL command of the relevant introduction, the command can calculate the number of lines of the file, because the frequency of use is not very much to see, you can try to see.

This article is from the "Dream to Reality" blog, please be sure to keep this source http://lookingdream.blog.51cto.com/5177800/1841357

An explanation of the use of the NL command under Linux