The NL command is used in a Linux system to calculate the line number of a file. NL can be output file content automatically add line number, its default result and cat-n a bit different, NL can do more than the line number 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: The calculation does not start again 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:
[Root @localhost test]# nl log2012.log
1 2012-01
2 2012-02
3 ======
[Root @localhost test]#
Note: The blank line in the file, NL will not add the line number;
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:
[Root @localhost test]# nl-b a Log2012.log
1 2012-01
2 2012-02
3
4
5 ======
[Root @localhost test]#
Example 3: Make the line number preceded by 0, unified output format
command: Nl-b a-n RZ Log2014.log | Nl-b a-n rz-w 3 Log2014.log
Output:
[Root @localhost 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, to adjust the number of bits can be added to the parameter-W 3 is adjusted to 3 bits.
