Difference between revisions of "Linux/C3/The-grep-command/English-timed"
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|00:41 | |00:41 | ||
| − | |First let us know about regular expressions. | + | |First let us know about '''regular expressions'''. |
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|01:11 | |01:11 | ||
| − | |'''grep''' searches for one or more patterns in one or more | + | |'''grep''' searches for one or more patterns in one or more lines, paragraphs or a file. |
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|02:10 | |02:10 | ||
| − | |So press ''' | + | |So press '''Ctrl + Alt and T''' keys simultaneously on your keyboard. |
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|02:18 | |02:18 | ||
| − | |'''grep space (within double quotes) computers after the double quotes space grepdemo .txt''' | + | |'''grep space''' (within double quotes) '''computers''' after the double quotes '''space grepdemo .txt''' |
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|02:46 | |02:46 | ||
| − | |This is because '''grep''' searched for the pattern | + | |This is because '''grep''' searched for the pattern “computers” with small '''c'''. |
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|03:00 | |03:00 | ||
| − | |To make it '''case''' | + | |To make it '''case insensitive''', we need to use the '''minus i ''' (-i) option with '''grep'''. |
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|03:06 | |03:06 | ||
|From back to our terminal, now type: | |From back to our terminal, now type: | ||
| − | '''grep space (minus) i space (within double quotes) “computers” after the double quotes space grepdemo.txt''' | + | '''grep space (minus) i space''' (within double quotes) '''“computers”''' after the double quotes '''space grepdemo.txt''' |
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|03:48 | |03:48 | ||
| − | |We can also store this result in another file | + | |We can also store this result in another file. |
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|06:26 | |06:26 | ||
| − | |Suppose we may only want to know the '''number of matches '''or '''count'''. | + | |Suppose, we may only want to know the '''number of matches '''or '''count'''. |
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|07:03 | |07:03 | ||
| − | |* To see the | + | |* To see the contents of a file |
**eg. '''cat filename''' | **eg. '''cat filename''' | ||
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|07:50 | |07:50 | ||
| − | |And* To know the count | + | |And * To know the count |
**eg.''' grep -c “Fail” grepdemo.txt'''. | **eg.''' grep -c “Fail” grepdemo.txt'''. | ||
Revision as of 14:29, 12 March 2015
| 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. |
| 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 (-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 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. |
| 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 contents of a file
|
| 07:07 | * To list the entries of a particular stream
|
| 07:14 | * To ignore cases
|
| 07:21 | * Lines that do not match the pattern
|
| 07:30 | * To list the line numbers with the entries
|
| 07:38 | * To store the result in another file
|
| 07:50 | And * To know the count
|
| 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 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 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, signing off. Thank you for joining. |
