shell筆記之sed編輯器的基礎用法（下）

 1、本篇從刪除行開始講起

 文本替換命令只是sed編輯器多種命令用法之一，若是咱們工做當中，須要刪除文本中特定的文本行或者字符串，那就要用到sed編輯器的刪除命令了.

刪除命令爲d,它將刪除全部與命令匹配的文本行或字符串。使用刪除命令要當心，由於在命令執行的過程當中包含尋址模式，若是忘記尋址模式，全部文本行都會從文本流中刪除。

$ sed 'd' test2.txt

注意，上述命令我只是掩飾d的用法，加上-i參數，才能真正刪除整個文本的內容。切忌，刪除前，必定要記得用尋址模式，下面咱們演示利用尋址模式，刪除文本中特定的行。

$ sed '3d' test2.txt
this is script test, we are test bash shell
this is script test, we are test bash shell
this is script test, we are test bash shell
this is script test, we are test bash shell

發現沒，文本中共有五行，刪除了第三行，因此就變成四行了。

再來作個刪除特定文本行範圍的實例：

$ sed '2,3d' test2.txt
this is script test, we are test bash shell
this is script test, we are test bash shell
this is script test, we are test bash shell

 使用特殊的文件結束符，來指定要刪除的一段文本行

$ sed '3,$d' test2.txt
this is script test, we are test bash shell
this is script test, we are test bash shell

 sed編輯器的模式匹配功能也一樣適用於刪除命令

 sed '/number 1/d' test2.txt
this is script test, we are test bash shell
this is script test, we are test bash shell
this is script test, we are test bash shell
this is script test, we are test bash shell

這一步要注意，sed編輯器不會處理原始文件，所刪除的全部文本行僅從sed編輯器輸出中刪除，原始文件仍然包含這些「已刪除的行」。

 再來練習一個刪除指定行範圍的例子

$  sed '/1/,/3/d' test2.txt
this is script test, we are test bash shell
this is script test, we are test bash shell

 

2、插入和附加文本

 與其餘編輯器同樣，sed編輯器也能夠在數據流中插入和附加文本。兩個操做之間有必定的差異，千萬不要搞混淆了哦

  
  
  
  

   
   
   
   
插入命令(i)在指定行以前添加新的一行  
   
   
   
   
附加命令(a)在指定行以後添加新的一行 
  
  
  
  

 這兩個命令格式比較容易混淆，不能在單命令行上使用這兩個命令，必須單獨要插入和附加的行。格式以下：

sed '[address]command\
new line'

 new line 中的文本出如今sed輸出中指定的位置，使用插入命令，文本出如今該數據流文本以前，例子以下：

$ echo "testing"|sed 'i\
> this is a test'
this is a test
testing

 然而，在使用附加命令的時候，文本就出如今該數據流文本以後，示例以下：

$ echo "testing"|sed 'a\
> this is a test'
testing
this is a test

 (a) ,(i)這兩個命令，也能夠用在數據流內部進行文本插入和附加處理，在特定文本行上處理：

$ sed '3i\
> this is a dog line test' test2.txt
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is a dog line test
this is script test, we are test bash shell 3
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

在第三行，成功插入this is a dog line test

 接下來，咱們在將this is a dog line test插入到第三行以後：

 $ sed '3a\
> this is a dog line test' test2.txt
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is script test, we are test bash shell 3
this is a dog line test
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

 若是數據流有多行，而您又須要在此數據流末尾附加新的一行文本，那麼你可使用美圓符號（$），它表示尾行，示例：

$ sed '$a\
> this is a dog line test' test2.txt
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is script test, we are test bash shell 3
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5
this is a dog line test

 要插入或附加多行文本，必需要在每一行插入或附加的新文本行以前使用一個反斜槓，直到到達要插入或者附加文本行的最後一行：

$ sed '1i\
> this is a dog test line\
> this is a beautiful test' test2.txt
this is a dog test line
this is a beautiful test
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is script test, we are test bash shell 3
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

 

3、更改行

更改行命令用於更改數據流中整行文本內容，工做方式與插入和附加命令相同，所以必須與其餘命令獨立執行。示例：

$ sed '3c\
> this is new correct line' test2.txt
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is new correct line
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

在本例中，sed編輯器更改了第三行文本內容，咱們也可使用文本模式進行更改：

$ sed '/number 3/c\
> this is new right script' test2.txt
this is script test, we are test bash shell 1
this is script test, we are test bash shell 2
this is new right script
this is script test, we are test bash shell 5
this is script test, we are test bash shell 5

 文本模式更改命令將更改與全部文本模式匹配的文本行：

$ sed '/number 1/c\
> this is a beautiful test script' test2.txt
this is a beautiful test script
this is script test, we are test bash shell 2
this is script test, we are test bash shell 3
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

 在更改命令中，可使用地址範圍，可是結果卻不是預期要達到的結果。

$ sed '2,3c\
> this is a beautiful test script' test2.txt
this is script test, we are test bash shell 1
this is a beautiful test script
this is script test, we are test bash shell 4
this is script test, we are test bash shell 5

 

執行後，結果倒是把2,3兩行變成了一行更改後的文本。因此這點要注意！