Difference between revisions of "BOSS-Linux/C3/The-sed-command/English-timed"

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|editing function like insertion, substitution and deletion in matched text.
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|editing functions like insertion, substitution and deletion in matched text.
  
 
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| Let us first start with some examples.
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| Let us start with some examples.
  
 
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|I have a file called '''seddemo.txt''' in '''home''' directory version.  
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|I have a file called '''seddemo.txt''' in the '''home''' directory.  
  
 
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|Now, suppose we want to print the second line of the file.
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|Now suppose, we want to print the second line of the file.
  
 
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|For this, we need to open the terminal.  
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|For this, we need to open the '''terminal'''.  
  
 
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|'''sed''' space within  single quotes ‘'''2p’''' after the single quotes space '''seddemo.txt'''
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|'''sed''' space within  single quotes '''2p''' after the single quotes space '''seddemo.txt'''
  
 
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|Here '''2''' denotes the location which is the second line.
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|Here, '''2''' denotes the location which is the second line.
  
 
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|'p' denotes the action which is printing ('''p''').
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|'p' denotes the action which is printing.
  
 
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|This is the default behavior of the action '''p'''.
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|This is the default behavior of action '''p'''.
  
 
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|type: '''sed '''space  '''-n''' space (Within single quotes) '''2p''' after the single quotes space '''seddemo.txt '''
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|type: '''sed '''space  '''-n''' space (within single quotes) '''2p''' after the single quotes space '''seddemo.txt '''
  
 
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|'''p''' indicates the action we want to take i.e. to print the second line.
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|'''p''' indicates the action we want to take i.e. to print the second line
  
 
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|This is the general syntax of ''''sed'''' '''command'''.
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|This is the general syntax of ''''sed' command'''.
  
 
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|'''sed''' space  '''-n''' space within single quotes (dollar) '''$p''' after the single quotes space '''seddemo.txt '''
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|'''sed''' space  '''-n''' space within single quotes dollar-sign '''p''' after the single quotes space '''seddemo.txt '''
  
 
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|'''sed''' space  '''-n''' space within single quotes '''3''' (comma) ''',6p’''' space '''seddemo.txt '''
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|'''sed''' space  '''-n''' space within single quotes '''3''' comma '''6p''' after the single quotes space '''seddemo.txt'''
  
 
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|Say, if we had to print all lines except from 3rd to 6th we will type:
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|Say, if we had to print all lines except from 3rd to 6th, we will type:
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'''sed''' space  '''-n''' space within single quotes ‘'''3''' (comma) ''',6''' (exclamation mark) '''!p'''  
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'''sed''' space  '''-n''' space within single quotes '''3''' comma '''6''' (exclamation mark) '''!p'''  
  
 
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|This is known as '''line addressing'''.
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|This is known as '''line addressing''';
  
 
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|Address specified by the line numbers.
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|address specified by the line numbers.
  
 
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|Another way of addressing is '''Context addressing'''
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|Another way of addressing is '''Context addressing'''.
  
 
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|If we want to take actions on lines that contain a particular word, we use context addressing.
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|If we want to take actions on lines that contain a particular word, we use '''context addressing'''.
  
 
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|Come back to our editor.
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|Come back to our text editor.
  
 
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|'''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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|'''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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|'''sed''' space '''-n''' space (within single quotes) (front slash) (opening square bracket)  '''[cC] (closing square bracket)omputers/w''' space '''computer_student.txt''' after the single quotes space '''seddemo.txt '''
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|'''sed''' space '''-n''' space within single-quotes front-slash opening square-bracket '''[cC]''' closing square-bracket '''omputers/w''' space '''computer_student.txt''' after the single quotes space '''seddemo.txt'''
  
 
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|Now all the matching lines would be transferred to the file '''computer_student.txt'''.  
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|Now, all the matching lines would be transferred to the file '''computer_student.txt'''.  
  
 
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| Type: '''cat''' space '''computer_student'''.txt
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| Type: '''cat''' space '''computer_student.txt'''
  
 
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| Type: '''sed''' space '''-n''' space '''-e''' space (within single quotes) (front slash) '''‘/electronics/w''' space '''electro.txt’''' after the single quotes space  '''-e''' space (within single quotes) (front slash) '''‘/civil/w''' space '''civil.txt’''' after the single quote  space '''seddemo.txt '''
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| Type: '''sed''' space '''-n''' space '''-e''' space (within single quotes) (front slash) '''‘/electronics/w''' space '''electro.txt’''' after the single quotes space  '''-e''' space (within single quotes) (front slash) '''‘/civil/w''' space '''civil.txt’''' after the single quote  space '''seddemo.txt'''
  
 
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|Here '''-e''' is used to combine multiple methods.
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|Here, '''-e''' is used to combine multiple methods.
  
 
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|Use the same text file "seddemo.txt".
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|use the same text file "seddemo.txt".
  
 
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Revision as of 20:52, 13 August 2015

Time Narration
00:01 Welcome to this spoken tutorial on sed - the stream editor.
00:07 In this tutorial, we will learn usage of sed command.
00:11 We will do through some examples.
00:14 To record this tutorial,
00:16 I am using Linux Operating System and GNU BASH version 4.2.24
00:26 Please note, GNU bash version 4 or above is recommended to practice this tutorial.
00:33 As prerequisites,
00:35 you should know basics of Linux terminal.
00:38 For relevant tutorials, please visit our website which is as shown: http://spoken-tutorial.org
00:44 Let us start with an introduction to sed.
00:47 sed is a stream editor.
00:50 sed finds some pattern of text in a particular location of a file.
00:57 It performs some display or editing function-
01:01 editing functions like insertion, substitution and deletion in matched text.
01:10 Let us start with some examples.
01:13 We will see how to print using the sed command.
01:18 I have a file called seddemo.txt in the home directory.
01:23 Let us view its contents.
01:26 In this file, we have some entries like- roll no, name, stream, marks, pass or fail and the stipend amount.
01:38 Now suppose, we want to print the second line of the file.
01:43 For this, we need to open the terminal.
01:47 Now, type:
01:48 sed space within single quotes 2p after the single quotes space seddemo.txt
01:57 Press Enter.
02:00 Here, 2 denotes the location which is the second line.
02:05 'p' denotes the action which is printing.
02:09 Now look at the output.
02:11 It shows the entire file but see that the second line is printed twice.
02:18 This is the default behavior of action p.
02:22 To only print the second line,
02:25 type: sed space -n space (within single quotes) 2p after the single quotes space seddemo.txt
02:37 Press Enter.
02:40 We see only the second line is printed.
02:44 -n stands for ‘silent mode’ which will suppress all unnecessary output.
02:51 Then we give the location in the stream that we want to edit or display.
02:57 We want to select the second line.
03:00 p indicates the action we want to take i.e. to print the second line
03:06 and seddemo.txt is the name of the file.
03:11 This is the general syntax of 'sed' command.
03:15 Now, let us print the last line of the file.
03:20 Let me clear the prompt.
03:24 Now, type:
03:25 sed space -n space within single quotes dollar-sign p after the single quotes space seddemo.txt
03:36 Press Enter.
03:39 We see that the last line is printed.
03:42 Now come back to text editor.
03:45 Suppose, we want to print the entries from 3rd to 6th.
03:50 For this, we need to type on the terminal:
03:54 sed space -n space within single quotes 3 comma 6p after the single quotes space seddemo.txt
04:07 Press Enter.
04:09 The output is displayed from the third line to the sixth line.
04:14 Any of the actions can be reversed by using the exclamation mark (!) before the action.
04:21 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

04:38 After the single quotes space seddemo.txt
04:45 Press Enter.
04:46 The output is displayed.
04:49 Let us switch back to our slides.
04:52 Line addressing and context addressing.
04:56 So far, we specified the lines in the file on which the action needs to be taken.
05:02 This is known as line addressing;
05:05 address specified by the line numbers.
05:08 This is one way of addressing.
05:11 Another way of addressing is Context addressing.
05:16 Lines that contain particular context say a particular word.
05:21 If we want to take actions on lines that contain a particular word, we use context addressing.
05:29 Regular expressions can be used.
05:32 Let us see an example.
05:35 Come back to our text editor.
05:38 Say, we want to print those lines which have the word "computers".
05:44 Come back to our terminal.
05:46 Now, type:
05:48 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
06:14 Press Enter.
06:16 We see the lines with the word "computers" is displayed.
06:22 We write pattern within square-brackets.
06:24 This is to match any one or both of the characters within square-brackets.
06:30 When we need to match patterns, the pattern needs to be typed between front slashes.
06:37 We can print it in a file as well using the w option.
06:43 For this, type:
06:44 sed space -n space within single-quotes front-slash opening square-bracket [cC] closing square-bracket omputers/w space computer_student.txt after the single quotes space seddemo.txt
07:11 Press Enter.
07:14 Now, all the matching lines would be transferred to the file computer_student.txt.
07:21 Let us view the contents.
07:25 Type: cat space computer_student.txt
07:32 Press Enter.
07:35 We see the entries.
07:37 We can also have patterns that we can write to different files.
07:42 Let us clear the prompt.
07:45 Type: sed space -n space -e space (within single quotes) (front slash) ‘/electronics/w space electro.txt’ after the single quotes space -e space (within single quotes) (front slash) ‘/civil/w space civil.txt’ after the single quote space seddemo.txt
08:18 Press Enter.
08:22 Here, -e is used to combine multiple methods.
08:27 This would create two files- electro.txt and civil.txt.
08:34 To see what they contain, type:
08:37 cat space electro.txt
08:42 This will display the entries with the word "electronics".
08:47 Let us see the content of "civil" file.
08:50 Type: cat space civil.txt
08:55 press Enter.
08:57 This will display the entries having the word "civil".
09:01 We will see some more set of commands in another tutorial.
09:05 I will use the same program.
09:08 This brings us to the end of this tutorial.
09:11 Let us switch back to our slide.
09:14 we will summarize.
09:15 In this tutorial, we learnt: sed
09:18 * To print using sed.
09:19 * Line Addressing.
09:21 * Context Addressing.
09:23 As an assignment,
09:25 use the same text file "seddemo.txt".
09:28 Try to print records from 6th to 12th line.
09:33 Watch the video available at the link shown below.
09:36 It summarizes the Spoken Tutorial project.
09:39 If you do not have good bandwidth, you can download and watch it.
09:44 The Spoken Tutorial project team:
09:46 Conducts workshops using spoken tutorials.
09:49 Gives certificates to those who pass an online test.
09:53 For more details, please write to contact@spoken-tutorial.org
10:00 Spoken Tutorial project is a part of the Talk to a Teacher project.
10:04 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
10:11 More information on this mission is available at: http://spoken-tutorial.org\NMEICT-Intro
10:17 This is Ashwini Patil from IIT Bombay, signing off. Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14

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