View source for Linux-AWK/C2/Basics-of-awk/English-timed

{| border=1
| '''Time'''
| '''Narration'''

|-
|  00:01
| Welcome to the spoken tutorial on the '''awk''' command.

|-
|00:05 
|  In this tutorial we will learn, '''awk command.'''

|-
| 00:09
| We will do this through some examples.

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| 00:12
| To record this tutorial, I am using
*Ubuntu Linux 12.04 OS
*GNU BASH v. 4.2.24

|-
| 00:23
| Please note, GNU Bash version 4 or above is recommended to practice this tutorial.

|-
| 00:29
| Let us start with an introduction to '''awk'''.

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| 00:33
| The''' awk''' command is a very powerful text manipulation tool.

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| 00:38
| It is named after its authors, '''Aho, Weinberger''' and '''Kernighan'''.

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| 00:44
| It can perform several functions. 

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| 00:46
| It operates at the field level of a record. 

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| 00:51
| So, it can easily access and edit the individual fields of the record.

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| 00:56
| Let us see some examples. 

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| 00:59
| For demonstration purpose, we use the''' awkdemo.txt '''file. 

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| 01:04
| Let us see the contents of '''awkdemo.txt''' file.

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| 01:09
| Now open the '''terminal''' by pressing 
'''CTRL + ALT''' and '''T''' keys simultaneosuly on your keyboard.

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| 01:17
| Let us see how to print using '''awk command.''' 

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| 01:22
| Type:
'''awk space''' (within single quote) (front slash) ‘'''/Pass '''(front slash)'''/'''(opening curly bracket) '''{print (closing curly bracket)}''' (after the  quotes) '''space awkdemo.txt''' 

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| 01:38
| Press '''Enter'''

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| 01:40
|Here '''Pass''' is the selection criterion. 

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| 01:44
| All the lines of the '''awkdemo''' where '''Pass''' occurs are printed. 

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| 01:49
| The action here is print. 

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| 01:52
| We can also use '''regular expressions''' in '''awk'''

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| 01:56
| Say we want to print records of students with name '''Mira.'''

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| 02:01
| We would type:
'''awk space '/M opening square bracket [ ei closing square bracket ]*ra */{ print}' space awkdemo.txt'''

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| 02:27
| Press '''Enter.'''

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| 02:29
| '''"*"'''  will give one or more occurrences of previous character.

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| 02:33
| Thus entries with more than one occurrence for '''i, e''' and '''a''' will be listed.

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| 02:40
| For example 

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| 02:42
| *Mira

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|02:45 
| *Meera

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| 02:47
| *Meeraa

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| 02:52
| '''awk''' supports the '''extended regular expressions (ERE)'''.

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| 02:58
| Which means we can match multiple patterns separated by a '''PIPE'''.
|-
|03:03
|Let me clear the promt

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|03:05
|Now type:

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| 03:10
| '''awk space (in single quotes)(front slash) ‘/civil (vertical bar)'''|electrical '''(front slash)'''/{print}'''' '''awkdemo.txt'''

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| 03:23
| Press '''Enter.'''

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| 03:26
| Now entries for both '''civil''' and '''electrical''' are given.

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| 03:31
|  Let us go back to our slides. 

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| 03:34
| Parameters '''awk''' has some special parameters to identify individual fields of a line. 

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| 03:41
| '''$1(Dollar 1)''' would indicate the first field. 

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| 03:45
| Similarly we can have '''$2, $3''' and so on for respective fields. 

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| 03:53
| '''$0''' represents the entire line.

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|03:56
|come back to our terminal

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| 03:59
|Note that each word is separated by '''PIPE''' in the file '''awkdemo.txt.'''

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| 04:05
| In this case '''PIPE '''is called a '''delimiter.'''

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| 04:09
| A '''delimiter''' separates words from each other.

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| 04:13
| A '''delimiter''' can also be a single '''whitespace. '''

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| 04:16
| To specify a '''delimiter''', we have to give '''- capital F '''flag followed by a '''delimiter'''.

|-
|04:24
| Let us see 

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| 04:25
| Type '''awk space minus capital F space''' within double quotes''' PIPE space''' within single quote '''front slash civil PIPE electrical front slash ''' within curly braces''' print space dollar0 space awkdemo.txt'''

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| 04:51
| Press '''Enter'''

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| 04:53
| This print the entire line since we have used '''$0.'''

|-
| 04:58
| Notice that, '''names''' and '''stream of students''' are the second and third fields.

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| 05:04
|Say we only want to print two fields.

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| 05:08
| We will replace '''$0''' with '''$2 and$3''' in the above command.

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| 05:15
| Press '''Enter '''

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| 05:18
| Only two fields are shown.

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| 05:21
| Though it gives the right result, the display is all jagged and unformatted. 

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| 05:26
|  We can provide formatted output by using the '''C''' style '''printf '''statement. 

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| 05:32
| We can also provide a serial number by using a builtin variable '''NR'''. 

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| 05:40
| We will see more about builtin variables later.

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| 05:44
| Now Type
'''awk''' space '''-F”|”''' space ''''/Pass/{printf “%4d %-25s %-15s \n”,''' '''NR,$2,$3 }'''' space '''awkdemo.txt''' 

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| 06:33
| '''Press Enter.'''

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| 06:34
| We see the difference.

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| 06:37
| Here the '''NR''' stands for number of records. 

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| 06:41
| Records are '''integers''', hence we have written''' %d'''. 

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| 06:45
| '''Name''' and '''Stream''' are '''strings'''. So we have used '''%s'''. 

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| 06:50
| Here '''25s''' will reserve 25 spaces for '''Name''' field.

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| 06:55
| '''15s''' will reserve 15 spaces for '''Stream''' field.

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| 07:01
| The '''minus sign''' is used to left justify the output.

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| 07:05
| This brings us to the end of this tutorial.

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| 07:08
| Let us move back to our slides.

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| 07:10
| Let us summarize.

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| 07:11
| In this tutorial we learnt To print using awk

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| 07:16
| Regular expression in awk To list the enteries for a paritcular stream

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| 07:21
| To list only the second and the third fileds

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| 07:24
| To display a formatted output

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| 07:28
| As an assignment 

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|07:29 
| Display roll no., stream and marks of Ankti Saraf

|-
| 07:34
|  Watch the video available at the link shown below

|-
| 07:37
| It summarises the Spoken Tutorial project

|-
| 07:40
| If you do not have good bandwidth, you can download and watch it

|-
|07:45
|The Spoken Tutorial Project Team Conducts workshops using spoken tutorials

|-
| 07:48
| Gives certificates to those who pass an online test

|-
| 07:52
| For more details, please write to contact@spoken-tutorial.org

|-
| 07:58
|Spoken Tutorial Project is a part of the Talk to a Teacher project

|-
| 08:01
| It is supported by the National Mission on Education through ICT,MHRD,Government of India

|-
| 08:07
| More information on this Mission is available at:  [http://spokentutorial.org\NMEICT-Intro]

|-
| 08:12
|This is Ashwini Patil from IIT Bombay signning off. Thank you for joining.

|}