Difference between revisions of "Linux/C3/The-sed-command/English-timed"
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|I have a file called '''seddemo.txt''' in '''home directory''' version. | |I have a file called '''seddemo.txt''' in '''home directory''' version. | ||
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| − | + | |Let us view its contents. | |
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| − | |Press '''Enter'''. | + | |Press '''Enter'''.We see that the last line is printed. |
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| − | |Now type: | + | |Now type:'''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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| − | |We see the entries. | + | |We see the entries.We can also have patterns that we can write to different files. |
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| − | | | + | | To print using sed.Line Addressing. |
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| − | | | + | | Context Addressing. |
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Revision as of 12:38, 10 March 2017
| Time | Narration |
| 00:01 | Welcome to this spoken tutorial on sed - the stream editor. |
| 00:05 | In this tutorial, we will learn usage of sed command. |
| 00:11 | We will do this through some examples. |
| 00:14 | To record this tutorial, |
| 00:16 | I am using Ubuntu Linux version 12.04 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. |
| 00:34 | As prerequisites, |
| 00:36 | you should know basics of Linux terminal. |
| 00:39 | For relevant tutorials please visit our website which is as shown: http://spoken-tutorial.org |
| 00:45 | Let us start with an introduction to sed: |
| 00:48 | sed is a stream editor. |
| 00:51 | sed finds some pattern of text in a particular location of a file. |
| 00:58 | It performs some display or editing function- |
| 01:02 | editing function 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. |
| 01:19 | I have a file called seddemo.txt in home directory version. |
| 01:24 | 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. |
| 01:39 | Now, suppose we want to print the second line of the file. |
| 01:44 | For this, we need to open the terminal by pressing Ctrl + Alt and T keys simultaneously on your keyboard. |
| 01:53 | Now Type: |
| 01:55 | sed space within single quotes ‘2p’ after the single quotes space seddemo.txt |
| 02:03 | Press Enter. |
| 02:06 | Here, 2 denotes the location which is the second line. |
| 02:11 | p denotes the action, which is printing(p). |
| 02:16 | Now Look at the output. |
| 02:18 | It shows the entire file but see that the second line is printed twice. |
| 02:25 | This is the default behavior of the action p. |
| 02:29 | To only print the second line, |
| 02:31 | type: |
| 02:33 | sed space -n space (Within single quotes) 2p after the single quotes space seddemo.txt |
| 02:44 | Press Enter. |
| 02:46 | We see only the second line as printed. |
| 02:51 | -n stands for ‘silent mode’ which will suppress all unnecessary output. |
| 02:58 | Then we give the location in the stream that we want to edit or display. |
| 03:03 | We want to select the second line. |
| 03:07 | p indicates the action we want to take i.e to print the second line. |
| 03:12 | And seddemo.txt is the name of the file. |
| 03:18 | This is the general syntax of sed command. |
| 03:21 | Now let us print the last line of the file. |
| 03:26 | Let me clear the prompt. |
| 03:29 | Now type: |
| 03:32 | sed space -n space within single quotes (dollar) $p after the single quotes space seddemo.txt |
| 03:42 | Press Enter.We see that the last line is printed. |
| 03:49 | Now come back to our text editor. |
| 03:51 | Suppose we want to print the entries from 3rd to 6th. |
| 03:57 | For this, we need to type on the terminal: |
| 04:00 | sed space -n space within single quotes 3 (comma) ,6p’ space seddemo.txt |
| 04:14 | Press Enter. |
| 04:16 | The output is displayed from the third line to the sixth line. |
| 04:21 | Any of the actions can be reversed by using the exclamation mark before the action. |
| 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 |
| 04:44 | after the single quotes space seddemo.txt |
| 04:51 | Press Enter. |
| 04:53 | The output is displayed. |
| 04:56 | Let us switch back to our slides. |
| 04:58 | Line addressing and context addressing. |
| 05:03 | So far, we specified the lines in the file on which the action needs to be taken. |
| 05:09 | This is known as line addressing- |
| 05:12 | address specified by the line numbers. |
| 05:15 | This is one way of addressing. |
| 05:18 | Another way of addressing is Context addressing- |
| 05:22 | lines that contain particular context say a particular word. |
| 05:28 | If we want to take actions on lines that contain a particular word, we use context addressing. |
| 05:36 | Regular expressions can be used. |
| 05:39 | Let us see an example. |
| 05:42 | Come back to our text editor. |
| 05:44 | Say, we want to print those lines which have the word computers. |
| 05:50 | Come back to our terminal. |
| 05:53 | Now type:sed space -n space within single quotes front slash (opening square bracket) [cC] (Closing Square bracket) omputers/p after the single quotesspace seddemo.txt |
| 06:20 | Press Enter. |
| 06:23 | We see the lines with the word "computers" is displayed. |
| 06:28 | We write pattern within square brackets. |
| 06:31 | This is to match any one or both of the characters within square brackets. |
| 06:36 | When we need to match patterns, the pattern needs to be typed between front slashes. |
| 06:43 | We can print it in a file as well, using the w option. |
| 06:50 | For this type: |
| 06:52 | 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 |
| 07:18 | Press Enter. |
| 07:21 | Now all the matching lines would be transferred to the file computer_student.txt. |
| 07:27 | Let us view the content of computer_student |
| 07:31 | Type: cat space computer_student.txt |
| 07:38 | Press Enter. |
| 07:42 | We see the entries.We can also have patterns that we can write to different files. |
| 07:50 | Let us clear the prompt. |
| 07:52 | 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 |
| 08:24 | Press Enter |
| 08:28 | Here -e is used to combine multiple methods. |
| 08:34 | This would create two files electro.txt and civil.txt. |
| 08:41 | To see what they contain, type: |
| 08:43 | cat space electro.txt |
| 08:49 | This will display the entries with the word "electronics". |
| 08:54 | Let us see the contents of civil file. |
| 08:58 | Type: cat space civil.txt |
| 09:01 | press Enter. |
| 09:03 | This will display the entries having the word "civil". |
| 09:08 | We will see some more set of commands in another tutorial. |
| 09:12 | I will use the same program. |
| 09:14 | This brings us to the end of this tutorial. |
| 09:18 | Let us switch back to our slide. |
| 09:20 | we will summarize, |
| 09:22 | In this tutorial we learnt, sed: |
| 09:25 | To print using sed.Line Addressing. |
| 09:27 | Context Addressing. |
| 09:30 | As an assignment, |
| 09:32 | use the same text file seddemo.txt, |
| 09:35 | try to print records from 6th to 12th line. |
| 09:40 | Watch the video available at the link shown below. |
| 09:42 | It summarizes the Spoken Tutorial project. |
| 09:46 | If you do not have good bandwidth, you can download and watch it. |
| 09:51 | The Spoken Tutorial Project Team: |
| 09:53 | Conducts workshops using spoken tutorials |
| 09:55 | Gives certificates to those who pass an online test. |
| 10:00 | For more details, please write tocontact@spoken-tutorial.org. |
| 10:07 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 10:11 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 10:18 | More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro. |
| 10:25 | This is Ashwini Patil from IIT Bombay, signing off . Thank You for joining. |
