Difference between revisions of "Linux-AWK/C2/Basics-of-awk/English"
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| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial we will learn, | | style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial we will learn, | ||
− | awk command. | + | '''awk command.''' |
We will do this through some examples. | We will do this through some examples. | ||
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| style="border:1pt solid #000000;padding:0.176cm;"| To record this tutorial, I am using | | style="border:1pt solid #000000;padding:0.176cm;"| To record this tutorial, I am using | ||
− | Ubuntu Linux 12.04 OS | + | *Ubuntu Linux 12.04 OS |
+ | *GNU BASH v. 4.2.24 | ||
− | + | Please note, GNU Bash version 4 or above is recommended to practice this tutorial. | |
− | + | ||
− | Please note, GNU | + | |
|- | |- | ||
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 4 | | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 4 | ||
− | + | ||
Introduction | Introduction | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| | + | | style="border:1pt solid #000000;padding:0.097cm;"| Let us start with an introduction to '''awk'''. |
− | It is named after its authors, Aho, Weinberger and Kernighan. | + | The''' awk''' command is a very powerful text manipulation tool. |
+ | |||
+ | It is named after its authors, '''Aho, Weinberger''' and '''Kernighan'''. | ||
|- | |- | ||
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| style="border:1pt solid #000000;padding:0.097cm;"| Let us see some examples. | | style="border:1pt solid #000000;padding:0.097cm;"| Let us see some examples. | ||
− | For demonstration purpose we use the''' awkdemo.txt '''file. | + | For demonstration purpose, we use the''' awkdemo.txt '''file. |
Let us see the contents of '''awkdemo.txt''' file. | Let us see the contents of '''awkdemo.txt''' file. | ||
− | |||
− | |||
− | |||
|- | |- | ||
− | | style="border:1pt solid #000000;padding:0.176cm;"| Now open the terminal | + | | style="border:1pt solid #000000;padding:0.176cm;"| Now open the '''terminal''' by pressing |
− | '''CTRL + ALT and T | + | '''CTRL + ALT''' and '''T''' keys simultaneosuly on your keyboard. |
Line 84: | Line 82: | ||
"awk '/Pass/ {print}' awkdemo.txt<nowiki>" [</nowiki>enter] | "awk '/Pass/ {print}' awkdemo.txt<nowiki>" [</nowiki>enter] | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| Let us see how to print using awk command. | + | | style="border:1pt solid #000000;padding:0.097cm;"| Let us see how to print using '''awk command.''' |
Type: | Type: | ||
− | '''awk''' | + | '''awk space''' (within single quote) (front slash) ‘'''/Pass '''(front slash)'''/'''(opening curly bracket) '''{print (closing curly bracket)}''' (after the quotes) '''space awkdemo.txt''' |
Press '''Enter''' | Press '''Enter''' | ||
− | Here '''Pass''' is the selection criterion. | + | |- |
+ | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
+ | | style="border:1pt solid #000000;padding:0.097cm;"|Here '''Pass''' is the selection criterion. | ||
Line 105: | Line 105: | ||
"awk '/M<nowiki>[</nowiki>ei]*ra<nowiki>*/ {</nowiki>print}' awkdemo.txt<nowiki>" [</nowiki>enter] | "awk '/M<nowiki>[</nowiki>ei]*ra<nowiki>*/ {</nowiki>print}' awkdemo.txt<nowiki>" [</nowiki>enter] | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| We can also use regular expressions in awk | + | | style="border:1pt solid #000000;padding:0.097cm;"| We can also use '''regular expressions''' in '''awk''' |
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− | We would type: | + | |- |
+ | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
+ | | style="border:1pt solid #000000;padding:0.097cm;"|We would type: | ||
− | '''awk | + | '''awk space '/M opening square bracket [ ei closing square bracket ]*ra */{ print}' space awkdemo.txt''' |
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− | + | |- | |
+ | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
+ | | style="border:1pt solid #000000;padding:0.097cm;"| '''"*"''' will give one or more occurrences of previous character. | ||
− | Thus entries with more than one occurrence for i, e and a will be listed | + | Thus entries with more than one occurrence for '''i, e''' and '''a''' will be listed. |
− | For ex. Meera | + | For ex. |
− | + | *Meera | |
− | Mira | + | *Mira |
− | + | *Meeraa | |
− | Meeraa | + | |
|- | |- | ||
| style="border:1pt solid #000000;padding:0.097cm;"| | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| '''awk''' supports the extended regular expressions (ERE). | + | | style="border:1pt solid #000000;padding:0.097cm;"| '''awk''' supports the '''extended regular expressions (ERE)'''. |
− | Which means we can match multiple patterns separated by a PIPE. | + | Which means we can match multiple patterns separated by a '''PIPE'''. |
|- | |- | ||
Line 146: | Line 149: | ||
− | '''awk | + | '''awk space (in single quotes)(front slash) ‘/civil (vertical bar)'''|electrical '''(front slash)'''/{print}'''' '''awkdemo.txt''' |
− | ''' | + | Press '''Enter.''' |
Line 162: | Line 165: | ||
− | + | '''awk''' has some special parameters to identify individual fields of a line. | |
− | $1(Dollar 1) would indicate the first field. | + | '''$1(Dollar 1)''' would indicate the first field. |
− | Similarly we can have $2, $3 and so on for respective fields. | + | Similarly we can have '''$2, $3''' and so on for respective fields. |
− | $0 represents the entire line. | + | '''$0''' represents the entire line. |
|- | |- | ||
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− | A delimiter separates words from each other. | + | A '''delimiter''' separates words from each other. |
− | A delimiter can also be a single '''whitespace. ''' | + | A '''delimiter''' can also be a single '''whitespace. ''' |
− | + | ||
− | + | ||
− | + | ||
+ | To specify a '''delimiter''', we have to give '''- capital F '''flag followed by a '''delimiter'''. | ||
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− | | style="border:1pt solid #000000;padding:0.176cm;"| Lets go back to the terminal. | + | | style="border:1pt solid #000000;padding:0.176cm;"| Lets go back to the '''terminal'''. |
Line 208: | Line 209: | ||
− | '''awk | + | '''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''' |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
Press '''Enter''' | Press '''Enter''' | ||
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“awk -F"|" '/Pass/ {print $2, $3}' awkdemo<nowiki>” [</nowiki>enter] | “awk -F"|" '/Pass/ {print $2, $3}' awkdemo<nowiki>” [</nowiki>enter] | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| Notice that, names and stream of students are the second and third fields. | + | | style="border:1pt solid #000000;padding:0.097cm;"| Notice that, '''names''' and '''stream of students''' are the second and third fields. |
− | Say we only want to print two fields. | + | |- |
+ | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
+ | | style="border:1pt solid #000000;padding:0.097cm;"|Say we only want to print two fields. | ||
− | We will replace '''$0''' with '''$2 | + | We will replace '''$0''' with '''$2 and$3''' in the above command. |
− | + | Press '''Enter ''' | |
Only two fields are shown. | Only two fields are shown. | ||
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|- | |- | ||
| style="border:1pt solid #000000;padding:0.097cm;"| | | style="border:1pt solid #000000;padding:0.097cm;"| | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| Though it gives the right result the display is all jagged and unformatted. | + | | style="border:1pt solid #000000;padding:0.097cm;"| Though it gives the right result, the display is all jagged and unformatted. |
− | + | ||
− | + | ||
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− | | style="border:1pt solid #000000;padding:0.176cm;"| We can provide formatted output by using the C style '''printf '''statement. | + | | style="border:1pt solid #000000;padding:0.176cm;"| We can provide formatted output by using the '''C''' style '''printf '''statement. |
− | We can also provide a serial number by using a builtin variable NR. | + | We can also provide a serial number by using a builtin variable '''NR'''. |
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− | Here the NR stands for number of records. | + | Here the '''NR''' stands for number of records. |
− | + | Records are '''integers''', hence we have written''' %d'''. | |
− | Name and | + | '''Name''' and '''Stream''' are '''strings'''. So we have used '''%s'''. |
− | Here 25s will reserve 25 spaces for Name field. | + | Here '''25s''' will reserve 25 spaces for '''Name''' field. |
− | 15s will reserve for Stream field. | + | '''15s''' will reserve for '''Stream''' field. |
− | The minus sign is used to left justify the output. | + | The '''minus sign''' is used to left justify the output. |
− | |||
− | + | |- | |
+ | | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 8 | ||
+ | |style="border:1pt solid #000000;padding:0.176cm;"| This brings us to the end of this tutorial. | ||
+ | |||
+ | |||
+ | Let us move back to our slides. | ||
− | |||
− | |||
− | + | Let us summarize. | |
In this tutorial we learnt | In this tutorial we learnt | ||
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| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 9 | | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 9 | ||
− | | As an assignment | + | | style="border:1pt solid #000000;padding:0.176cm;" | As an assignment |
Display roll no., stream and marks of Ankti Saraf | Display roll no., stream and marks of Ankti Saraf | ||
Line 323: | Line 317: | ||
|- | |- | ||
− | | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide | + | | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 10 |
Acknowledgement Slide | Acknowledgement Slide | ||
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|- | |- | ||
− | | style="border:1pt solid #000000;padding:0.176cm;"| Display Slide | + | | style="border:1pt solid #000000;padding:0.176cm;"| Display Slide 11 |
Spoken Tutorial Workshops | Spoken Tutorial Workshops | ||
Line 353: | Line 347: | ||
|- | |- | ||
− | | style="border:1pt solid #000000;padding:0.176cm;"| Display Slide | + | | style="border:1pt solid #000000;padding:0.176cm;"| Display Slide 12 |
Acknowledgement | Acknowledgement |
Latest revision as of 16:32, 22 March 2018
Title of script: The Awk Command
Author: Sachin Patil and Anirban
Keywords: Selection criteria, action, formatted printing, fields, Regular expressions, Variables
|
|
Display Slide 1 | Welcome to the spoken tutorial on the awk command. |
Display Slide 2
Learning Objective |
In this tutorial we will learn,
awk command. We will do this through some examples. |
Display Slide 3
System requirement |
To record this tutorial, I am using
Please note, GNU Bash version 4 or above is recommended to practice this tutorial. |
Display Slide 4
Introduction |
Let us start with an introduction to awk.
The awk command is a very powerful text manipulation tool. It is named after its authors, Aho, Weinberger and Kernighan. |
Continue Slide
|
It can perform several functions.
It operates at the field level of a record. So, it can easily access and edit the individual fields of the record. |
Let us see some examples.
For demonstration purpose, we use the awkdemo.txt file. Let us see the contents of awkdemo.txt file.
| |
Now open the terminal by pressing
CTRL + ALT and T keys simultaneosuly on your keyboard.
|
Now open the terminal by pressing CTRL + ALT and T keys simultaneosuly on your keyboard. |
type:
|
Let us see how to print using awk command.
Type: awk space (within single quote) (front slash) ‘/Pass (front slash)/(opening curly bracket) {print (closing curly bracket)} (after the quotes) space awkdemo.txt
|
Here Pass is the selection criterion.
| |
Type
"awk '/M[ei]*ra*/ {print}' awkdemo.txt" [enter] |
We can also use regular expressions in awk
|
We would type:
| |
"*" will give one or more occurrences of previous character.
| |
awk supports the extended regular expressions (ERE).
Which means we can match multiple patterns separated by a PIPE. | |
Type
"awk '/civil|electrical/ {print}' awkdemo" [enter] |
Now type:
|
Display slide 7
|
Let us go back to our slides.
|
Switch to the terminal
|
Note that each word is separated by PIPE in the file awkdemo.txt.
|
Type
“awk -F "|" '/civil|electrical/ {print $0}' awkdemo ” [enter]
|
Lets go back to the terminal.
Press Enter This print the entire line since we have used $0. |
Type
“awk -F"|" '/Pass/ {print $2, $3}' awkdemo” [enter] |
Notice that, names and stream of students are the second and third fields.
|
Say we only want to print two fields.
Only two fields are shown. | |
Though it gives the right result, the display is all jagged and unformatted.
| |
“awk -F"|" '/Pass/ {printf "%4d %-25s %-15s \n",
NR,$2,$3 }' awkdemo” [enter]
|
We can provide formatted output by using the C style printf statement.
awk space -F”|” space '/Pass/{printf “%4d %-25s %-15s \n”, NR,$2,$3 }' space awkdemo.txt
We see the difference.
|
Display Slide 8
|
This brings us to the end of this tutorial.
In this tutorial we learnt To print using awk Regular expression in awk To list the enteries for a paritcular stream To list only the second and the third fileds To display a formatted output
|
Display Slide 9 | As an assignment
Display roll no., stream and marks of Ankti Saraf
|
Display Slide 10
Acknowledgement Slide
|
Watch the video available at the link shown below
It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it |
Display Slide 11
Spoken Tutorial Workshops
|
The Spoken Tutorial Project Team
Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact@spoken-tutorial.org |
Display Slide 12
Acknowledgement
|
Spoken Tutorial Project is a part of the Talk to a Teacher project
It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro |
No Last Slide for tutorials created at IITB
Display the previous slide only and narrate this line. |
The script has been contributed by Sachin Patil.
This is Ashwini Patil from IIT Bombay signning off. Thank you for joining. |