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LINUX AWK Tutorial Series | Chapter 9

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LINUX AWK Tutorial Series | Chapter 9

Hello, In this chapter I will continue the concepts of arrays in AWK.

Now I am going share, how are we going to use the arrays with the file. I will use the same file Employee data. I will mostly be using awk scripts in the examples.

Let's start with an example


Example 1: 

We want to calculate the food amount for each employee. That will be calculated based on the salary of the employee. That will be 1% of the total salary.

    
[himanshu@oel7 AWK]$ cat array_food
BEGIN{FS=","}
{
food[$1]=$4*.01
}
END{
for(i in food)
print i "==" food[i]
}

Confused about what for will do here. For loop will execute for each index in the array.




So here the array index would the name of the employees (food[$1]) and calculating the food amount based on the salary which is the 4th field.



Example 2: 

Now I want to delete the array for Robert in output.

Syntax

delete array_name[index]  ==> This will delete one array element
delete array_name[index]  ==> Delete entire array


[himanshu@oel7 AWK]$ cat array_food
BEGIN{FS=","}
{
food[$1]=$4*.01
}
END{
delete food["Robert"]
for(i in food)
print i "==" food[i]
}






Try at Home: With the below awk script please try to execute and see what output we get.

[himanshu@oel7 AWK]$ cat array_food
BEGIN{FS=","}
{
food[$1]=$4*.01
}
END{
delete food
for(i in food)
print i "==" food[i]
}




Example 3:

In earlier chapters, we have discussed built-in variables related to arrays, Lets see them in our scripts.

ARGC: Number of command-line arguments.  
ARGV: Array which stores command line arguments.

[himanshu@oel7 AWK]$ cat builtin_arry_var
BEGIN{
print ("Arguments total" ARGC);
for (i=0;i<=ARGC-1;i++)
print ARGV[i]
}


Here I am using both ARGC and ARGV. The first index at i=0 will take the awk as the first argument. so the total argument here would be 2.






Example 4:

One more built-in variable is ENVIRON. It is also an array of environmental variables.
The array index would be the environment variables name.





Here I am printing value for the environment variable USER using the normal method and using AWK also doing the same.


Hope these would be clear.



More chapters will continue.



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