Linux/C3/More-on-grep-command/English-timed

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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.
01:25 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 way.
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 in double quotes chaudhury after the quotes space hyphen ie space in 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 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 quotesopening 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
07:25 * 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.

Contributors and Content Editors

Gaurav, Madhurig, PoojaMoolya, Sandhya.np14