BOSS-Linux/C3/The-sed-command/English-timed
From Script | Spoken-Tutorial
| 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: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: 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.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. 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.In this tutorial, we learnt: sed |
| 09:18 | To print using sed.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. |
