awk syntax to invoke function with argument read from a file - unix

Question

I have a function
xyz()
{
x=$1*2
echo x
}
then I want to use it to replace a particular column in a csv file by awk.
File input.csv:
abc,2,something
def,3,something1
I want output like:
abc,4,somthing
def,6,something1
Command used:
cat input.csv|awk -F, -v v="'"`xyz "$2""'" 'BEGIN {FS=","; OFS=","} {$2=v1; print $0}'
Open file input.csv, calling function xyz by passing file 2nd filed as argument and result is stored back to position 2 of file, but is not working!
If I put constant in place of $2 while calling function it works:
Please help me to do this.
cat input.csv|awk -F, -v v="'"`xyz "14""'" 'BEGIN {FS=","; OFS=","} {$2=v1; print $0}'
This above line of code is working properly by calling the xyz function and putting the result back to 2nd column of file input.csv, but with only 14*2, as 14 is taken as constant.

Answer 1

There's a back-quote missing from your command line, and a UUOC (Useless Use of Cat), and a mismatch between variable v on the command line and v1 in the awk program:
cat input.csv|awk -F, -v v="'"`xyz "$2""'" 'BEGIN {FS=","; OFS=","} {$2=v1; print $0}'
^ Here ^ Here ^ Here
That should be written using $(…) instead:
awk -F, -v v="'$(xyz "$2")'" 'BEGIN {FS=","; OFS=","} {$2=v; print $0}' input.csv
This leaves you with a problem, though; the function xyz is invoked once by the shell before you start your awk script running, and is never invoked by awk. You simply can't do it that way. However, you can define your function in awk (and on the fly):
awk -F, 'BEGIN { FS = ","; OFS = "," }
function xyz(a) { return a * 2 }
{ $2 = xyz($2); print $0 }' \
input.csv
For your two-line input file, it produces your desired output.