Antarade: Created page with "'''Title of script: Built-in functions in awk ''' '''Author: Antara Roy Choudhury''' '''Keywords: awk Built-in function, Arithmetic function, String function, Input/Output f..."

2018-03-20T03:28:29Z

Created page with "'''Title of script: Built-in functions in awk ''' '''Author: Antara Roy Choudhury''' '''Keywords: awk Built-in function, Arithmetic function, String function, Input/Output f..."

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'''Title of script: Built-in functions in awk '''

'''Author: Antara Roy Choudhury'''

'''Keywords: awk Built-in function, Arithmetic function, String function, Input/Output function, Timestamps function, length(), substr(), int(), system()'''

{| style="border-spacing:0;"
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| <center>'''Narration'''</center>

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 1: Introduction
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Welcome to this spoken tutorial on''' built-in functions''' in '''awk'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 2: Learning Objectives
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In this tutorial we will learn about '''different types of built-in functions''' like-

* '''Arithmetic functions'''
* '''String functions'''
* '''Input/Output functions '''and
* '''Time stamps functions'''

We will do this through some examples.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 3: System requirement
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux '''16.04 OS and
* '''gedit text editor '''3.20.1

You can use any text editor of your choice.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 4: Prerequisite
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| To practice this tutorial, you should have gone through the earlier '''awk''' tutorials on this website.

You should have some knowledge of any programming language like '''C''' or '''C++'''.

If not, then please go through the corresponding tutorials on our website.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 5: Code Files
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The files used in this tutorial are available in the '''Code Files''' link on this tutorial page.

Please download and extract them.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 6: Arithmetic Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''Built-in functions''' are always available for '''awk''' to call.

First we will learn about the '''arithmetic functions.'''

* '''sqrt(x) function''' returns positive square root of a number x
* '''int(x)''' truncates '''x''' to an integer value
* '''exp(x)''' gives the exponential of x

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 6: Arithmetic Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| * '''log(x)''' returns natural logarithm value of x
* '''sin(x)''' and '''cos(x)''' give sine(x) and cosine(x) respectively
* Please note that '''argument x '''should be mentioned in '''radians'''.

Let’s look at an example to understand these '''functions'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show arithmetic_function.awk

in Gedit
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| I have already written the code in a file '''arithmetic underscore function dot awk'''

The same is available in the '''Codefiles''' link

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight print statements for sqrt ()
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Here, we are printing the square root of a positive and negative number respectively.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight print statements for

int ()
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Next we are printing the integer value for a positive and negative number respectively.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight print statements for exp ()
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Then we are printing exponential of a small number and a very large number.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight print statements for

log ()
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| After that, natural logarithms of positive and negative numbers are printed.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight print statements for sine and cosine ()
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We are also printing '''sine''' and '''cosine''' values of '''0.52 radian''', that is actually '''30 degree.'''

Let us execute the file in the '''terminal.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Open the terminal by pressing Ctrl, Alt and T Keys.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| <nowiki>cd /<saved folder></nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Next go to the folder where you have downloaded and extracted the file using '''cd''' command.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type:

awk -f arithmetic_function.awk
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now type '''awk space -f arithmetic_function.awk '''

And press '''Enter '''to see the output.

Couple of things are clear from this output.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight Square root of positive

Highlight Square root of negative

Highlight int for positive & negative

Highlight exp of positive

Highlight exp of negative

Highlight log of positive

Highlight log of negative

Highlight sine & cosine
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| '''sqrt() function''' gives square root of a positive number.

It returns '''nan''' or not a number if the number is negative.

'''int()''' gives the truncated integer of any positive or negative number.

'''exp()''' gives exponential of a number.

If the number is very large, the '''function''' will return '''inf'''.

Natural logarithm of positive number is given by '''log() function'''.

If the number if negative, the '''function '''returns '''nan'''.

'''Sine '''and '''cosine functions '''return corresponding values.

You can verify the value using your calculator.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 7: Random Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now, let’s look at '''random functions.'''

* '''rand()''' returns any random number between 0 and 1.
* But never returns 0 or 1.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 7: Random Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| * Generated numbers will be random within one '''awk '''execution.
* But predictable across different executions of the awk program. 

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 7: Random Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| * '''srand(x)''' is used to provide '''seed value x''' for '''random function.'''
* In absence of '''x''', date and time of day is used as the '''seed value.'''

Let us understand these with an example.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show random.awk in Gedit
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| I have written a code for the '''random function '''and saved it as '''random.awk'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight rand ()

Highlight rand()*50

<nowiki>Highlight for (i=1;i<=5;i++)</nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Here, inside the '''for loop, rand() function '''will generate a random number between 0 and 1.

Then the generated number will be multiplied by 50 and get printed.

So, this code will generate 5 random numbers within 50.

Switch to the '''terminal''' and execute the file.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type

awk -f random.awk
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type:

'''awk space hyphen f space random dot awk''' and press '''Enter.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output

Press up key and enter
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| See, it is giving 5 random numbers.

What happens if I execute the code again?

Press the Up arrow key to get the previously executed command and press '''Enter'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output and highlight
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We are getting the same output.

Which means, '''awk '''is generating the same set of random numbers for every execution of the script.

Then how can we get a new set of random numbers in every execution?

Switch to the code once again.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type

<nowiki>srand() and [enter]</nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Before the '''for loop''', type '''srand()'''

Press Crtl and S keys to the save the file.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now switch to the '''terminal.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Press up key and enter
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Press the Up arrow key to get the previously executed command and press '''Enter'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now we have a new set of random numbers in the output.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Press up key and enter
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Let us execute once again

Press the Up arrow key and press '''Enter'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| It is giving a different set of random numbers.

So, we can generate a new set of random numbers using '''srand function''', when it’s used without an '''argument'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 8: String Functions
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Next will see some '''string functions'''.

'''length(s)''' gives the length of a particular string '''s'''

'''index(s1,s2) function''' determines the position of''' string s2 '''within the larger '''string s1.'''

For example, '''index("linux","n")''', returns 3.

Let us see an example.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| show awkdemo.txt in gedit
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Open the file '''awkdemo.txt'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the file opened and highlight rollnumber column
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We know that each student in the '''awkdemo.txt '''file has a 4 digit rollnumber.

Due to typing error, the roll numbers may have wrong number of digits.

We can easily detect these using '''awk commands.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In terminal Type:

awk -F"|" 'length($1)!=4 {print}' awkdemo.txt

Highlight 'length($1)!=4 {print}'

<nowiki>[Enter]</nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the '''terminal '''and''' '''type the '''command '''as shown here.

Here we are checking the length of the 1st field is equal to 4 or not.

If not, then that particular record will get printed.

Press '''Enter'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| See, there is '''one '''roll-number '''S02''' that has been typed incorrectly.

It has three digits, whereas all others have four digits.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 9: Substring function
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The '''substr(s,a,b) function '''extracts a '''substring '''from a larger '''string s.'''

Let me explain the parameters.

* Here '''s''' is the '''string'''
* '''a''' denotes the position in '''s '''from which the extraction would start
* '''b''' denotes the number of characters that would be extracted.

Let us see one example.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show awkdemo.txt in Gedit
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Switch to the''' awkdemo.txt''' file.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the file opened

| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The first letter of the roll numbers represents the '''Hostel code''' where the particular student resides.

Say we want to find the list of students, who are staying in Hostel '''A'''.

To get that, let’s switch to the '''terminal'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type

awk -F"|" 'substr($1,1,1)=="A" {print $1,$2}' awkdemo.txt
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type the command as shown here.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight substr($1,1,1)
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Here we take the '''string''' denoted by '''$1'''.

As we know '''$1''' represents the first '''field''', that is roll number in our case.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight substr($1,1,1)
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Next, we extract a '''substring''' that starts at position '''one''' with the character length '''one'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Highlight <nowiki>=="A" </nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Then, if it is equal to capital '''A''', then that line from the file will get printed.

Press '''Enter''' to see the output.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We got the list of students who are in Hostel '''A'''.

|-
| style="background-color:#9fc5e8;border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 10: Split function
| style="background-color:#9fc5e8;border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| We have seen the '''function split''' earlier.

So, I am not explaining the details here.

Please refer to the earlier awk tutorials if you have any doubt.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 11: I/O Functions

| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| There are some other '''functions''' which are related to '''Input/Output'''.

* '''system() function''' - helps us to run any '''unix command '''within '''awk'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"|
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now, we will run the '''unix command date''' through '''awk command.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Type

awk 'BEGIN{system("date")}'

<nowiki>[Enter]</nowiki>
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In the '''terminal''' type:

'''awk space''' single quote in capital letters '''BEGIN''' opening curly brace '''system '''inside parentheses and double quotes '''date '''closing curly brace single quotes

And press '''Enter.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Show the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Today’s date and time is displayed on the '''terminal''' as an output.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Hover your mouse on the command

awk 'BEGIN{system("date")}'
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Now, why do we need this?

We have kept only the '''BEGIN''' section of the '''awk command. '''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Hover your mouse on the output
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| In real world scenarios, we may want to print the '''system date, '''before displaying the required output.

In that case, we would need to execute '''system commands''' from '''awk command.'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 12: Time Stamps
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| There are some '''functions''' dealing with '''time stamps''' like

* '''systime()'''
* '''strftime() '''
* etc.

Browse through the Internet to know about these '''functions'''.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 13: Summary
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| This brings us to the end of this tutorial.

Let us summarize.

In this tutorial we learnt about different types of '''built-in functions''' like

* '''Arithmetic functions'''
* '''String functions'''
* '''Input/Output functions'''
* '''Time stamps functions'''

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 14: Assignment

| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| As an assignment-

Write an '''awk''' program to print the last '''field''' of every record

* where name of the student has small '''u''' as the third letter using the '''awkdemo.txt '''file.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 15:

About Spoken Tutorial project
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 16:

Spoken Tutorial workshops
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The '''Spoken Tutorial Project''' team conducts workshops using spoken tutorials.

And gives certificates on passing online tests.

For more details, please write to us.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 17:

Forum for specific questions:
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 18: Acknowledgement
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at

this link.

|-
| style="border-top:0.035cm solid #000001;border-bottom:0.035cm solid #000001;border-left:0.035cm solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| Slide 19: Thank You
| style="border:0.035cm solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.079cm;padding-right:0.191cm;"| The script has been contributed by Antara.

And this is Praveen from IIT Bombay signing off.

Thank you for joining

|}

Linux-AWK/C2/Built-in-Functions-in-awk/English - Revision history

Nancyvarkey: Nancyvarkey moved page Linux/C3/Built-in-Functions-in-awk/English to Linux-AWK/C2/Built-in-Functions-in-awk/English without leaving a redirect: New series

Nancyvarkey at 12:06, 21 March 2018

Antarade: Created page with "'''Title of script: Built-in functions in awk ''' '''Author: Antara Roy Choudhury''' '''Keywords: awk Built-in function, Arithmetic function, String function, Input/Output f..."

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