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

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.
03:13	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.
04:12	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 to contact@spoken-tutorial.org
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: http://spoken-tutorial.org\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