1. 命令解析

命令用途：

將文件內容輸出到標準輸出，并添加上行號；若沒有指定文件，或指定的文件名為-則讀取標準輸入作為數據源；

命令格式：

nl [OPTION]... [FILE]...

命令參數：

-b, --body-numbering=STYLE use STYLE for numbering body lines
-d, --section-delimiter=CC use CC for separating logical pages
-f, --footer-numbering=STYLE use STYLE for numbering footer lines
-h, --header-numbering=STYLE use STYLE for numbering header lines
-i, --line-increment=NUMBER line number increment at each line
-l, --join-blank-lines=NUMBER group of NUMBER empty lines counted as one
-n, --number-format=FORMAT insert line numbers according to FORMAT
-p, --no-renumber do not reset line numbers at logical pages
-s, --number-separator=STRING add STRING after (possible) line number
-v, --starting-line-number=NUMBER first line number on each logical page
-w, --number-width=NUMBER use NUMBER columns for line numbers
--help display this help and exit
--version output version information and exit

2. 示例

2.1 無參顯示文件內容及行號(空行不顯示行號)

[root@test nlTest]# cat f1
This is
My
File

After blank
is still file content
[root@test nlTest]# nl f1
     1  This is
     2  My
     3  File
       
     4  After blank
     5  is still file content

2.2 顯示空行的行號 -b

[root@test nlTest]# nl -b a f1
     1  This is
     2  My
     3  File
     4  
     5  After blank
     6  is still file content

2.3 顯示行號且指定格式 -n

[root@test nlTest]# nl -n ln f1
1       This is
2       My
3       File
       
4       After blank
5       is still file content
[root@test nlTest]# nl -n rn f1
     1  This is
     2  My
     3  File
       
     4  After blank
     5  is still file content
[root@test nlTest]# nl -n rz f1
000001  This is
000002  My
000003  File
       
000004  After blank
000005  is still file content

2.4 指定格式位數 -n -w

[root@test nlTest]# nl -n rz -w 3 f1
001 This is
002 My
003 File
    
004 After blank
005 is still file content