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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.
00:12 To record this tutorial, I am using:
00:15 Linux Operating System and
00:18 GNU BASH version 4.2.24
00:22 Please note, GNU bash version 4 or above is recommended to practice this tutorial.
00:30 As prerequisites, you should know basics of Linux terminal.
00:34 For relevant tutorials, please visit our website which is as shown.
00:39 First, let us know about regular expressions .
00:43 * Regular expressions are pattern matching techniques.
00:47 * when we have to find out whether a pattern exists in a line, paragraph or a file.
00:54 For ex. If you want to search a phone number in the telephone directory
01:01 or to find a keyword in a paragraph or a line, we use grep command.

Let us move on to grep.

01:08 grep searches for one or more patterns in one or more lines, paragraph or a file.
01:15 If file-name is not mentioned, grep searches for the patterns in the standard input.
01:22 If filename is missing, grep searches for the patterns in the standard input.
01:28 I will demonstrate usage of grep using a demo file called grepdemo.txt.
01:35 Let us see the content of the file.
01:37 This is a file that has 13 entries.
01:41 Each entry has 6 fields- roll number, name, stream, marks and stipend amount.
01:50 The fields are separated by a bar which is called a delimiter.
01:55 Let us see how grep works.
01:58 Say, we want to use 'grep' command to see who are the students in the computers stream.
02:04 For this, we have to open the terminal.
02:07 Now, type on the terminal:
02:09 grep space (within double quotes) computers after the double quotes space grepdemo .txt
02:18 Press Enter.
02:20 This would enlist those entries where stream is computers.
02:25 Now, compare the result with the original file.
02:29 Come back to our text editor.
02:31 We see that the entry for Zubin is not enlisted.
02:37 Why this is so?
02:38 This is because grep searched for the pattern “computers” with small c
02:43 while for Zubin, the stream is “Computers” with a capital C.
02:48 The pattern matching is case sensitive.
02:51 To make it case insensitive, we need to use the minus i option with grep.
02:58 Come back to our terminal. Now, type:

grep space minus i space within double quotes computers after the double quotes space grepdemo.txt

03:12 Press Enter.This will now enlist all the four entries.
03:17 So we saw, grep enlists only those lines of files that match a given pattern.
03:23 We may do the reverse.
03:26 It is possible to make grep enlist only those lines that do not match the pattern.
03:32 For that, we have the minus v option.
03:35 Say, we want to enlist those entries of students who have not passed.
03:40 We can also store this result in another file.
03:43 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

04:02 Press Enter.
04:04 To see the content of the file, type: cat space notpass.txt .
04:11 Press Enter.The output is displayed.
04:15 Now, at the prompt, type:
04:17 grep space minus i space within double quotes fail after the double quotes space grepdemo.txt
04:28 and press Enter.
04:30 This is different.
04:32 This will include those students who are failed but their result is incomplete.
04:37 If we want to see the line number in the file at which the enlisted entries are, we have the minus n option.
04:46 Let us clear the prompt.
04:49 Now, type: grep space -in space within double quote "fail" after the double quotes space grepdemo.txt
05:01 Press Enter.
05:03 The line number is displayed.
05:06 The patterns so far have been of single word.
05:10 We may have multi-word patterns as well.
05:13 But the entire pattern must be within quotes.
05:17 So, type: grep space minus i space within double quotes ankit space saraf after the double quotes space grepdemo.txt
05:29 Press Enter.
05:31 We see that Ankit Saraf's record is displayed.
05:35 We can also find patterns in multiple files.
05:39 For this, type:

grep space minus i space within double quotes fail after double quotes space grepdemo.txt space notpass.txt

05:55 Press Enter.
05:57 The output is displayed.
05:59 With multiple files, grep will write the name of the file in which the entry was found. grepdemo.txt and notpass.txt.
06:10 These are the records from notpass.txt file and these are the records from grepdemo.txt file.
06:18 Suppose, we may only want to know the number of matches or count .
06:23 For that, we have the minus c option.
06:27 So, type: grep space minus c space within double quotes Fail with a capital F after the quotes space grepdemo.txt
06:40 Press Enter.
06:42 This will give us the count of number of lines matched.
06:46 This brings us to the end of this tutorial.
06:51 Let us summarize.
06:53 In this tutorial, we learnt:
06:55 To see the content of a file e.g. cat filename
06:59 To list the entries of a particular stream e.g. grep “computers” grepdemo.txt
07:06 To ignore cases e.g. grep -i “computers” grepdemo.txt
07:14 Lines that do not match the pattern e.g. grep -iv “pass” grepdemo.txt
07:22 To list the line numbers with the entries e.g. grep -in “fail” grepdemo.txt
07:31 To store the result in another file e.g. grep -iv “pass” grepdemo.txt notpass.txt and
07:41 To know the count e.g. grep -c “Fail” grepdemo.txt.
07:48 As an assignment,
07:50 explore some other commands like -E, + and ?.
07:56 Watch the video available at the link shown below.
07:58 It summarizes the Spoken Tutorial project.
08:01 If you do not have good bandwidth, you can download and watch it.
08:05 The Spoken Tutorial Project Team:
08:07 Conducts workshops using spoken tutorials.
08:11 Gives certificates to those who pass an online test.
08:14 For more details, please write
08:21 Spoken Tutorial project is a part of the Talk to a Teacher project.
08:25 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
08:32 More information on this mission is available at:\NMEICT-Intro
08:36 This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14