Difference between revisions of "Linux/C3/The-grep-command/English-timed"
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| − | |If file name is not mentioned,''' grep''' searches for the patterns in the standard input. | + | |If file name is not mentioned, '''grep''' searches for the patterns in the standard input. |
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| − | |So press '''Ctrl + Alt and T''' keys simultaneously on your keyboard. | + | |So press '''Ctrl + Alt''' and '''T''' keys simultaneously on your keyboard. |
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| − | |Press '''Enter | + | |Press '''Enter'''. This will now enlist all the four entries. |
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Latest revision as of 11:04, 17 October 2017
| 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 tocontact@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, signing off. Thank you for joining. |
