BOSS-Linux/C3/The-grep-command/English-timed
From Script | Spoken-Tutorial
| 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 tocontact@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. |
