Linux/C3/The-grep-command/English-timed

From Script | Spoken-Tutorial
Revision as of 17:37, 18 July 2014 by Pratik kamble (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
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 line, paragraph or a file.
01:17 If filename is not mentioned, grep search for the patterns in the standard input.


01:23 If filename 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
02:28 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?


02:46 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 option with grep.
03:06 From 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.
03:21 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.
04:12 To see the content of file, type:

cat space notpass.txt

04:20 Press Enter.
04:21 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.
04:38 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 multiword 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.
06:04 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 content 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,
07:58 Explore some other commands like -E, + and ?


08:04 Watch the video available at the link shown below.
08:06 It summarises 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 to

contact@spoken-tutorial.org

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: http://spoken-tutorial.org\NMEICT-Intro
08:45 This is Ashwini Patil from IIT Bombay signning off. Thank you for joining.

Contributors and Content Editors

Madhurig, PoojaMoolya, Pratik kamble, Sandhya.np14