Difference between revisions of "BOSS-Linux/C3/More-on-grep-command/English-timed"
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| − | |I will use the same file '''grepdemo.txt''' | + | |I will use the same file '''grepdemo.txt'''. |
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| − | |So, what is the solution? | + | |So, what is the solution? |
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| − | |Type: '''grep''' space '''hyphen ie''' space | + | |Type: '''grep''' space '''hyphen ie''' space within double quotes '''chaudhury''' ('c' 'h' 'a' 'u' 'd' 'h' 'u' 'r' 'y') after the quotes space '''hyphen ie''' space within double quotes '''chowdhari''' ('c' 'h' 'o' 'w' 'd' 'h' 'a' 'r' 'i') after the quotes space '''grepdemo.txt'''. |
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| − | |But there can be many other ways in which we can write the names. | + | |But, there can be many other ways in which we can write the names. |
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| 02:33 | | 02:33 | ||
| − | | A regular expression provides a concise and flexible means for matching '''string'''s of text | + | | A 'regular expression' provides a concise and flexible means for matching '''string'''s of text |
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| 02:56 | | 02:56 | ||
| − | |It allows us to specify a group of characters within a pair of square brackets . | + | |It allows us to specify a group of characters within a pair of square brackets. |
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| − | | To match '''chaudhury''', we may type at the prompt | + | | To match '''chaudhury''', we may type at the prompt: |
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| 03:22 | | 03:22 | ||
| − | |'''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''' | + | |'''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''' |
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| 04:13 | | 04:13 | ||
| − | |Suppose we like to match any digit we simply write [0-9]. | + | |Suppose we like to match any digit, we simply write [0-9]. |
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| 04:24 | | 04:24 | ||
| − | | The asterisk: The | + | | The asterisk: The asterisk refers to 0 or more occurrences of the immediately preceding character. |
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| 04:33 | | 04:33 | ||
| − | |For example '''ab asterisk''' can match '''a,ab,abb,abbb''' etc. | + | |For example, '''ab asterisk''' can match '''a,ab,abb,abbb''' etc. |
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| 04:50 | | 04:50 | ||
| − | |'''grep''' space '''hyphen i''' space within double quotes '''m opening square bracket '''ei''' closing square bracket asterisk '''r a a | + | |'''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''' |
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| 05:47 | | 05:47 | ||
| − | |Here the space within the quotes is important as it would match 5 or more letter words. | + | |Here, the space within the quotes is important as it would match 5 or more letter words. |
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| 06:04 | | 06:04 | ||
| − | |For that, we have the '''caret | + | |For that, we have the '''caret''' sign. |
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| 06:18 | | 06:18 | ||
| − | |We type at the prompt: '''grep ''' within double quotes '''caret-sign A''' after the quotes '''grepdemo.txt''' | + | |We type at the prompt: '''grep ''' space within double quotes '''caret-sign A''' after the quotes '''grepdemo.txt''' |
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| 06:34 | | 06:34 | ||
| − | | Similarly, to match a pattern at the end of the file, we have the '''dollar | + | | Similarly, to match a pattern at the end of the file, we have the '''dollar''' sign. |
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| 06:49 | | 06:49 | ||
| − | |'''grep''' space within double quotes | + | |'''grep''' space within double quotes opening square bracket 78 closing square bracket '''...''' '''dollar''' sign after the quotes space '''grepdemo.txt''' |
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| 07:05 | | 07:05 | ||
| − | |Press '''Enter ''' | + | |Press '''Enter '''. |
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| 07:15 | | 07:15 | ||
| − | | In this tutorial we learnt: | + | | In this tutorial, we learnt: |
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| 07:39 | | 07:39 | ||
| − | | As an assignment, list those entries that are 5 letters long and starts with Y. | + | | As an assignment, list those entries that are 5 letters long and starts with 'Y'. |
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Revision as of 21:12, 13 August 2015
| 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 on grep commands |
| 00:10 | through some examples. |
| 00:13 | To record this tutorial, I am using: |
| 00:16 | Linux Operating System and |
| 00:20 | GNU BASH version 4.2.24 |
| 00:23 | Please note, GNU bash version 4 or above is recommended to practice this tutorial. |
| 00:29 | As prerequisites- |
| 00:31 | * you should know basics of Linux terminal. |
| 00:35 | * You should be aware of grep. |
| 00:37 | For relevant tutorials, please visit our website which is as shown: http://spoken-tutorial.org |
| 00:43 | We can match more than one patterns as well. |
| 00:47 | Then we have to use the hyphen e option. |
| 00:52 | I will use the same file grepdemo.txt. |
| 00:57 | Say, we want to find information for those who are either in civil or electronics. |
| 01:04 | 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 within double quotes civil after the quotes space grepdemo.txt |
| 01:22 | Press Enter. |
| 01:24 | The output is displayed. |
| 01:27 | Say, you need to look into people whose title is choudhury. |
| 01:32 | The problem is, different people spell their titles in different way. |
| 01:38 | So, what is the solution? |
| 01:41 | In such cases, we can use hyphen e option with hyphen i. |
| 01:47 | Type: grep space hyphen ie space within double quotes chaudhury ('c' 'h' 'a' 'u' 'd' 'h' 'u' 'r' 'y') after the quotes space hyphen ie space within double quotes chowdhari ('c' 'h' 'o' 'w' 'd' 'h' 'a' 'r' 'i') after the quotes space grepdemo.txt. |
| 02:11 | Press Enter. |
| 02:14 | The output is displayed. |
| 02:16 | But, there can be many other ways in which we can write the names. |
| 02:22 | 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. |
| 02:51 | Let us see them one by one. |
| 02:54 | The character class- |
| 02:56 | 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. |
| 03:07 | Eg. [abc] would mean that this regular expression matches either a or b or c. |
| 03:17 | To match chaudhury, we may type at the prompt: |
| 03:22 | 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 |
| 03:53 | Press Enter. |
| 03:55 | The output is displayed. |
| 03:59 | It still does not match choudhuree with double e. |
| 04:02 | If we want to specify a large range then we write: |
| 04:07 | 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. |
| 04:43 | So, to match the students name whose name is Mira |
| 04:47 | We type at the prompt: |
| 04:50 | 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 |
| 05:11 | Press Enter. |
| 05:13 | 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. |
| 05:27 | We would simply type: |
| 05:30 | grep space within double quotes M... space after the quotes space grepdemo.txt |
| 05:43 | Press Enter. |
| 05:45 | The output is displayed. |
| 05:47 | 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. |
| 06:13 | We know that roll is the first field in the file. |
| 06:18 | We type at the prompt: grep space within double quotes caret-sign A after the quotes grepdemo.txt |
| 06:29 | Press Enter. |
| 06:31 | The output is displayed. |
| 06:34 | Similarly, to match a pattern at the end of the file, we have the dollar sign. |
| 06:40 | To find stipends between 7000 to 8999, we have to write: |
| 06:49 | grep space within double quotes opening square bracket 78 closing square bracket ... dollar sign after the quotes space grepdemo.txt |
| 07:05 | Press Enter . |
| 07:07 | The output is displayed. |
| 07:10 | This brings us to the end of this tutorial. |
| 07:13 | Let us summarize. |
| 07:15 | In this tutorial, we learnt: |
| 07:17 | * To match more than one pattern |
| 07:20 | * To check a word that has different spelling |
| 07:23 | * Character class |
| 07:24 | * The use of asterisk |
| 07:27 | * To match any one character using dot |
| 07:31 | * To match a pattern at the beginning of the file |
| 07:35 | * To match a pattern at the end of the file. |
| 07:39 | As an assignment, list those entries that are 5 letters long and starts with 'Y'. |
| 07:46 | Watch the video available at the link shown below. |
| 07:50 | It summarizes the Spoken Tutorial project |
| 07:53 | 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. |
| 08:04 | Gives certificates to those who pass an online test. |
| 08:08 | For more details, please write to contact@spoken-tutorial.org |
| 08:14 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 08:19 | 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, signing off. Thank you for joining. |
