Difference between revisions of "Linux/C3/More-on-grep-command/English-timed"
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Revision as of 15:17, 23 March 2017
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on More on grep. |
| 00:05 | In this tutorial we will learn |
| 00:07 | some more grep commands |
| 00:10 | through some examples. |
| 00:13 | To record this tutorial, I am using |
| 00:16 | Ubuntu Linux version 12.04 Operating System and |
| 00:20 | GNU BASH version 4.2.24 |
| 00:24 | Please note, GNU bash version 4 or above is recommended to practice this tutorial. |
| 00:31 | As prerequisites: |
| 00:33 | You should know basics of Linux terminal. |
| 00:36 | You should be aware of 'grep'. |
| 00:39 | For relevant tutorials, please visit our website which is as shown: http://spoken-tutorial.org |
| 00:45 | We can match more than one patterns as well. |
| 00:49 | Then we have to use the hyphen e option. |
| 00:53 | I will use the same file 'grepdemo.txt'. |
| 00:58 | Say, we want to find information for those who are either in civil or electronics. |
| 01:05 | We need to type on the terminal: |
| 01:07 | grep space hyphen e space within double quotes electronics after the quotes space hyphen e space in double quotes civil after the quotes space grepdemo.txt |
| 01:24 | Press Enter.The output is displayed. |
| 01:28 | Say, you need to look into people whose title is "choudhury". |
| 01:33 | The problem is, different people spell their titles in different ways. |
| 01:38 | So what is the solution?. |
| 01:42 | In such cases we can use hyphen e option with hyphen i. |
| 01:48 | Type:
grep space hyphen ie space within double quotes chaudhury after the quotes space hyphen ie space within double quotes chowdhari after the quotes space grepdemo.txt |
| 02:12 | Press Enter. |
| 02:14 | The output is displayed. |
| 02:16 | But there can be many other ways in which we can write the names. |
| 02:23 | How many hyphen e options can we give? |
| 02:26 | Obviously there needs to be a better way and that way is through Regular expressions. |
| 02:33 | A regular expression provides a concise and flexible means for matching strings of text |
| 02:41 | such as particular characters, words or patterns of characters. |
| 02:47 | There are a number of regular expression characters. |
| 02:52 | Let us see them one by one. |
| 02:55 | The character class: |
| 02:57 | It allows us to specify a group of characters within a pair of square brackets . |
| 03:03 | Only one out of this group of characters is matched. |
| 03:08 | Eg. [abc] would mean that this regular expression matches either a or b or c. |
| 03:18 | To match "chaudhury", we may type at the prompt: |
| 03:23 | grep space hyphen i space within double quotes ch opening square bracket ao closing square bracket opening square bracket uw closing square bracket dh opening square bracket ua closing square bracket r opening square bracket yi closing square bracket after the double quotes space grepdemo.txt |
| 03:54 | Press Enter. |
| 03:56 | The output is displayed. |
| 03:59 | It still does not match "choudhuree" with double 'e'. |
| 04:03 | If we want to specify a large range then we write: |
| 04:08 | First letter dash last letter of the range |
| 04:13 | Suppose we like to match any digit we simply write [0-9]. |
| 04:20 | One out of this group of characters is matched. |
| 04:24 | The Asterisk: The asterisk refers to 0 or more occurrences of the immediately preceding character. |
| 04:33 | For example ab asterisk can match a, ab, abb, abbb etc. |
| 04:44 | So, to match the student's name whose name is "Mira", |
| 04:48 | we type at the prompt: |
| 04:51 | grep space hyphen i space within double quotes m opening square bracket ei closing square bracket asterisk r a a asterisk after the quotes space grepdemo.txt |
| 05:12 | Press Enter. |
| 05:14 | The output is displayed. |
| 05:16 | The dot regular expression matches any one character. |
| 05:21 | Say, we want to search any words that are 4 letters long and starts with M. |
| 05:29 | We would simply type: |
| 05:31 | grep space within double quotes M... space after the quotes space grepdemo.txt |
| 05:44 | Press Enter. |
| 05:46 | The output is displayed. |
| 05:48 | Here, the space within the quotes is important as it would match 5 or more letter words. |
| 05:56 | We may be specific about where in the line we want to search for our pattern. |
| 06:01 | It may be at the beginning of the line. |
| 06:04 | For that we have the caret sign. |
| 06:07 | Now if we want to get those entries whose roll numbers start with A. |
| 06:14 | We know that roll is the first field in the file. |
| 06:19 | We type at the prompt: grep space within double quotes caret sign A after the quotes grepdemo.txt |
| 06:29 | Press Enter. |
| 06:32 | The output is displayed. |
| 06:35 | Similarly to match a pattern at the end of the file, we have the dollar sign. |
| 06:41 | To find stipends between 7000 to 8999 we have to write: |
| 06:50 | grep space within double quotes opening square bracket 78 closing square bracket ... dollar sign after the quotes space grepdemo.txt |
| 07:06 | Press Enter . |
| 07:08 | The output is displayed. |
| 07:11 | This brings us to the end of this tutorial. |
| 07:13 | Let us summarize. |
| 07:16 | In this tutorial we learnt: |
| 07:18 | To match more than one pattern |
| 07:20 | To check a word that has different spelling |
| 07:24 | Character class The use of asterisk |
| 07:28 | To match any one character using dot |
| 07:32 | To match a pattern at the beginning of the file |
| 07:35 | To match a pattern at the end of the file. |
| 07:40 | As an assignment,list those entries that are 5 letters long and starts with Y. |
| 07:48 | Watch the video available at the link shown below. |
| 07:51 | It summarizes the Spoken Tutorial project. |
| 07:54 | If you do not have good bandwidth, you can download and watch it. |
| 07:59 | The Spoken Tutorial Project Team conducts workshops using spoken tutorials, |
| 08:05 | gives certificates to those who pass an online test. |
| 08:08 | For more details, please write to contact@spoken-tutorial.org |
| 08:15 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 08:20 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 08:26 | More information on this Mission is available at the link shown below : http://spoken-tutorial.org\NMEICT-Intro |
| 08:32 | The script has been contributed by Anirban and Sachin. |
| 08:36 | This is Ashwini Patil from IIT Bombay, signning off. Thank you for joining. |
