View source for Linux/C3/The-sed-command/English-timed


{| border =1
|'''Time'''
|'''Narration'''

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| 00:01
|  Welcome to this spoken tutorial on the sed - the stream editor.

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| 00:05
|  In this tutorial  we will learn usage of '''sed '''command.

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|  00:11
|We will do through some examples

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| 00:14 
|To record this tutorial, 

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| 00:16
|I am using'''Ubuntu Linux'''  version 12.04''' Operating System''' and
'''GNU BASH''' version 4.2.24

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| 00:26 
|Please note,''' GNU bash''' version 4 or above is recommended to practice this tutorial.

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| 00:34
| As prerequisites

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| 00:36 
|You should know Basics of linux terminal

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| 00:39 
|For relevant tutorials please visit our website which as shown: http://spoken-tutorial.org 

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| 00:45
| Let us with an introduction to '''sed'''

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|00:48
|'''sed''' is a stream editor. 


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| 00:51 
|'''sed''' finds some pattern of text in a particular location of a file. 

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|  00:58
|It performs some display or editing function

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| 01:02 
|editing function like insertion, substitution and deletion in matched text.

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| 01:10
| Let us first start with some examples.

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|01:13  
|We will see how to print using the '''sed''' command.

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|  01:19
|I have a file called '''seddemo.txt''' in home directory.
version 

 |-
 | 01:24
 |Let us view its content.

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|  01:26
|In this file we have some enteries like roll no, name, stream, marks, pass or fail and the stipend amount.

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| 01:39
|Now suppose we want to print the second line of the file.

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|  01:44
|For this we need to oepn the terminal by pressing
CTRL + ALT and T keys simultaneously on your keyboard.

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| 01:53
|Now Type

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| 01:55
|'''sed''' space within  single quotes ‘'''2p’''' after the single quotes space '''seddemo.txt'''

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|  02:03
|'''Press Enter'''

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| 02:06
|Here '''2''' denotes the location which is the second line.

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|  02:11
|'''p''' denotes the action, which is printing('''p''').

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| 02:16 
|Now Look at the output.

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|  02:18
|It shows the entire file but see that the second line is printed twice.

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|  02:25
|This is the default behaviour of the action '''p'''.

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| 02:29
|To only print the second line

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| 02:31 
|Type: 

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|  02:33
|'''sed '''space  '''-n''' space (Within single quotes) '''2p''' after the single quotes space '''seddemo.txt '''

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|  02:44
|'''Press Enter.'''

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|02:46
|We see only the second line as printed.

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| 02:51
| '''-n''' stands for ‘silent mode’ which will suppress all unnecessary output.

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|  02:58
|Then we give the location in the stream that we want to edit or display. 

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|  03:03
|We want to select the second line.

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|  03:07
|'''p''' indicates the action we want to take ie to print the second line.


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|  03:12
|And '''seddemo.txt''' is the name of the file

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|  03:18
|This is the general syntax of sed command.

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| 03:21
|Now let us print the last line of the file.

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|03:26
|Let me clear the promt

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|  03:29
|Now Type 

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| 03:32 
|'''sed''' space  '''-n''' space within single quotes (dollar) '''$p''' after the single quotes space '''seddemo.txt '''

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|  03:42
|Press '''Enter'''.

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|  03:43
|We see that the last line is printed.

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|  03:49
|Now come back to text editor.

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| 03:51
| Suppose we want to print the enteries from 3rd to 6th



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| 03:57 
|For this we need to type on the terminal: 

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|  04:00
|'''sed''' space  '''-n''' space within single quotes '''3''' (comma) ''',6p’''' space '''seddemo.txt '''

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|  04:14
|'''Press Enter.'''

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|  04:16
|The output is displayed from the third line to the sixth line.

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| 04:21
| Any of the actions can be reversed by using the exclamation mark before the action.

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|  04:28
|Say if we had to print all lines except from 3rd to 6th we will type:
'''sed''' space  '''-n''' space within single quotes ‘'''3''' (comma) ''',6''' (exclamation mark) '''!p''' 

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| 04:44
|After the single quotes space '''seddemo.txt '''

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|  04:51
|'''Press''' '''Enter.'''

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|  04:53
|The output is displayed.

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|  04:56
|Let us switch back to our slides.

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|  04:58
|Line addressing and context addressing.

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| 05:03
| So far, we specified the lines in the file on which the action needs to be taken.



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|  05:09
|This is known as line addressing. 

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|  05:12
|Address specified by the line numbers.

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|  05:15
|This is one way of addressing.

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| 05:18 
|Another way of addressing is '''Context addressing'''

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|  05:22
|Lines that contain particular context say a particular word.

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|  05:28
|If we want to take actions on lines that contain a particular word we use context addressing.

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|  05:36
|Regular expressions can be used. 

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|  05:39
|Let us see an example.

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|  05:42
|Come back to our editor.

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| 05:44
|  Say we want to print those lines which have the word '''computers'''.

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|  05:50
|Come back to our temrinal.

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|  05:53
|Now Type



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|  05:54
|'''sed''' space  '''-n''' space (within single quotes) (front slash)(opening square bracket) [cC] (Closing Square bracket)  omputers/p after the single quotes'''space '''seddemo.txt '''

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|  06:20
|'''Press''' '''Enter.'''

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|  06:23
|We see the lines with the word computers is displayed.

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|  06:28
|We write pattern within square brackets. 

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|  06:31
|This is to match any one or both of the characters within square brackets.

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| 06:36 
|When we need to match patterns the pattern needs to be typed between front slashes.

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| 06:43
| We can print it in file as well using the '''w''' option. 

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|  06:50
|For this type:

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|  06:52
|'''sed''' space '''-n''' space (within single quotes) (front slash) (opening square bracket)  '''[cC] (closing square bracket)Computers/w''' space '''computer_student.txt''' after the space '''seddemo.txt '''

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|  07:18
|'''Press''' '''Enter.'''

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|  07:21
|Now all the matching lines would be transferred to the file '''computer_student.txt'''. 

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| 07:27
| Let us view the content of '''computer_student'''

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|  07:31
| Type '''cat''' space '''computer_student'''.txt

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|  07:38
|'''Press Enter.'''

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|  07:42
|We see the entries

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| 07:43
| We can also have patterns that we can write to different files. 

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|  07:50
| Let us clear the promt 

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|  07:52
| Type '''sed''' space '''-n''' space '''-e''' space (within single quotes) (front slash) '''‘/electronics/w''' space '''electro.txt’''' after the single quotes  '''-e''' space (within single quotes) (front slash) '''‘/civil/w''' space '''civil.txt’''' after the single quote  space '''seddemo.txt '''

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|  08:24
|Press '''Enter'''

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|  08:28
|Here '''-e''' is used to combine multiple methods''' '''

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|08:34
|This would create two files '''electro.txt''' and '''civil.txt'''. 

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|08:41
| To see what they contain type:

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|  08:43
|'''cat '''space''' electro.txt''' 

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|  08:49
|This will display the enteries with the word electronics.


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|  08:54
|Let us see the content of civil file.

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|  08:58
| Type '''cat '''space''' civil.txt'''

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|  09:01
|''' press Enter'''

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|  09:03
|This will display the enteries having the word civil.

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| 09:08
| We will see some more set of commands in another tutorial.

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|  09:12
|I will use the same program.

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|09:14
|This brings us to the end of this tutorial.

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|09:18
|Let us switch back to our slide

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| 09:20
| we will  summarize,

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|  09:22
|In this tutorial we learnt,

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| 09:24 
|sed.

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|  09:25
|To print using sed.



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|  09:26
|Line Addressing. 

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|  09:27
|Context Addressing.

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| 09:30
|  As an assignment,

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|  09:32
|Use the same text file '''seddemo.txt.'''

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|  09:35
|Try to print records from 6th to 12th line.

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| 09:40
| Watch the video available at the link shown below

|-
|  09:42
|It summarises the Spoken Tutorial project

|-
|  09:46
|If you do not have good bandwidth, you can download and watch it

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| 09:51
|  The Spoken Tutorial Project Team

|-
|  09:53
|Conducts workshops using spoken tutorials

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| 09:55 
|Gives certificates to those who pass an online test

|-
|  10:00
|For more details, please write tocontact@spoken-tutorial.org

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| 10:07
|  Spoken Tutorial Project is a part of the Talk to a Teacher project

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|  10:11
|It is supported by the National Mission on Education through ICT, MHRD, Government of India

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|  10:18
|More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro

|-
| 10:25
|This is Ashwini from IIT Bombay signing off . Thank You for joining.

|}