awk script

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1

Hey guys. Im trying to create a script that Create a one-line script named awkscript.sh that uses awk to read its standard input and extract the column of input given as an argument on the command line.
What do i put in vi?
For example: (the script name is awkscript.sh)
$ echo a b c d e f | ./awkscript.sh 1
a
$ echo a b c d e f | ./awkscript.sh 2
b
$ echo a b c d e f | ./awkscript.sh NF
f

2

Put this code in file: awkscript.sh

p="$1"

awk -v P="$p" '
{
        for (i=1; i<=NF; i++)
        {
                if (i == P)
                        print $i
                if (P == "NF" && i == NF)
                        print $i
        }
} '
3

Or..
Put this in your script..

awk -v var="$1" '{ print var!="NF"?$var:$NF}'
4

works perfectly :slight_smile: thank you. Im a noobie to learning awk. Can you explain to me that full command?

awk -v var="$1" '{ print var!="NF"?$var:$NF}'

5

Have you tried mine solution..?

$ cat test.sh
awk -v var="$1" '{ print var!="NF"?$var:$NF}'

$ echo a b c d e f | ./test.sh NF
f

$ echo a b c d e f | ./test.sh 4
d
6

yes it worked. I mistyped it. sorry

7

It's ok..

awk -v var="$1"  #    It uses var for saving $1(number which are passed to the script is $1).

'{ print var!="NF"?$var:$NF}' #    Here we check if variable var is not equal to "NF". If it is a number/not equal to "NF" then directly print $var(print that column value). 
                                If it is "NF" then print $NF.

Hope this helps you
Pamu

8

Thanks so much! this helped a lot! I understand until the point ?$var:$NF. I dont understand that part.

9

This can be written as..

Condition?True:False

Here we are using var!=NF as condition.
If condition satisfies then execute true part. If condition fails then execute false part.

As var is not equal to "NF" then print $var

And if var is equal to "NF" then print $NF

10

Again, thank you! Explained very well :slight_smile: