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Time Narration
00:01 Welcome to the spoken tutorial on grep command.
00:05 In this tutorial we will learn grep command.
00:09 We will do this with the help of some examples.
00:11 To record this tutorial, I am using
00:15 Ubuntu Linux 12.04 Operating System
00:20 and GNU BASH version 4.2.24.
00:24 Please note, GNU bash version 4 or above is recommended to practice this tutorial.
00:32 As prerequisites you should know basics of Linux terminal.
00:36 For relevant tutorials, please visit our website which is as shown.
00:41 First let us know about regular expressions.
00:45 Regular expressions are pattern matching techniques
00:50 when we have to find out whether a pattern exist in a line, paragraph or a file.
00:56 For ex. If you want to search a phone number in the telephone directory
01:02 or to find a keyword in a paragraph or a line, we use grep command.Let us move on to grep.
01:11 grep searches for one or more patterns in one or more lines, paragraphs or a file.
01:17 If file name is not mentioned, grep searches for the patterns in the standard input.
01:23 If file name is missing, grep searches for the patterns in the standard input.
01:30 I will demonstrate usage of grep using a demo file called grepdemo.txt.
01:37 Let us see the content of the file.
01:40 This is a file that has 13 entries.
01:44 Each entry has 6 fields: roll number, name, stream, marks, and stipend amount.
01:52 The fields are separated by a bar, which is called a delimiter.
01:56 Let us see how grep works.
02:00 Say we want to use grep command, to see who are the students in the computers stream.
02:07 For this we have to open the terminal.
02:10 So press Ctrl + Alt and T keys simultaneously on your keyboard.
02:16 Now type on the terminal:
02:18 grep space (within double quotes) computers after the double quotes space grepdemo .txt
02:27 Press Enter.This would enlist those entries where stream is computers.
02:33 Now compare the result with the original file.
02:37 Come back to our text editor.
02:40 We see that the entry for Zubin is not enlisted.
02:45 Why this is so? This is because grep searched for the pattern “computers” with small c.
02:52 While for Zubin, the stream is “Computers” with a capital C.
02:57 The pattern matching is case sensitive.
03:00 To make it case insensitive, we need to use the minus i (-i) option with grep.
03:06 Come back to our terminal, now type:grep space (minus) i space (within double quotes) “computers” after the double quotes space grepdemo.txt
03:20 Press Enter. This will now enlist all the four entries.
03:25 So we saw, grep enlists only those lines of files that match a given pattern.
03:32 We may do the reverse.
03:34 It is possible to make grep enlist only those lines that do not match the pattern.
03:40 For that we have the minus v option.
03:43 Say, we want to enlist those entries of students who have not passed.
03:48 We can also store this result in another file.
03:52 For this type: grep space minus iv space within double quotes pass after the double quotes space grepdemo.txt space greater than sign space notpass.txt
04:11 Press Enter. To see the content of file, type: cat space notpass.txt
04:20 Press Enter.The output is displayed.
04:24 Now at the prompt type:
04:26 grep space minus i space' within double quotes fail after the double quotes space grepdemo.txt
04:37 And Press Enter.This is different.
04:41 This will include those students who are failed but their result is incomplete.
04:46 If we want to see the line number in the file at which the enlisted entries are, we have the minus n option
04:54 Let us clear the prompt.
04:58 Now type grep space -in space within double quote "fail" after the double quotes space grepdemo.txt.
05:09 Press Enter.
05:11 The line number is displayed.
05:15 The patterns so far have been of single word.
05:18 We may have multi-word patterns as well.
05:21 But the entire pattern must be within quotes.
05:24 So, type: grep space minus i spacewithin double quotes ankit space saraf after the double quotes space grepdemo.txt
05:38 Press Enter.
05:40 We see that Ankit Saraf's record is displayed.
05:44 We can also find patterns in multiple files.
05:48 For this, type: grep space minus i space within double quotes fail after double quotes space grepdemo.txt space notpass.txt
06:03 Press Enter. The output is displayed.
06:07 With multiple files, grep will write the name of the file in which the entry was found. grepdemo.txt and notpass.txt.
06:18 These are the records from notpass.txt file and these are the records from grepdemo.txt file.
06:26 Suppose, we may only want to know the number of matches or count.
06:31 For that, we have the minus c option.
06:35 So, type: grep space minus c spacewithin double quotes Fail with a capital F after the quotes space grepdemo.txt
06:48 Press Enter.
06:50 This will give us the count of number of lines matched.
06:55 This brings us to the end of this tutorial.
06:59 Let us summarize.
07:01 In this tutorial we learnt:
07:03 To see the contents of a file eg. cat filename
07:07 To list the entries of a particular stream eg. grep “computers” grepdemo.txt
07:14 To ignore cases eg. grep -i “computers” grepdemo.txt
07:21 Lines that do not match the pattern eg. grep -iv “pass” grepdemo.txt
07:30 To list the line numbers with the entries eg. grep -in “fail” grepdemo.txt
07:38 To store the result in another file eg. grep -iv “pass” grepdemo.txt > notpass.txt
07:50 And To know the count eg. grep -c “Fail” grepdemo.txt.
07:57 As an assignment,Explore some other commands like -E, + and ?.
08:04 Watch the video available at the link shown below.
08:06 It summarizes the Spoken Tutorial project.
08:10 If you do not have good bandwidth, you can download and watch it.
08:14 The Spoken Tutorial Project Team:
08:16 Conducts workshops using spoken tutorials
08:19 Gives certificates to those who pass an online test.
08:23 For more details, please write
08:30 Spoken Tutorial Project is a part of the Talk to a Teacher project.
08:33 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:40 More information on this Mission is available at:\NMEICT-Intro.
08:45 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

Madhurig, PoojaMoolya, Pratik kamble, Sandhya.np14