mjhjmtu

Consider this function:

function add_one(in_ar, each) 
 for (each in in_ar) 
 in_ar[each]++
 

I would like to modify it such that if a second array is provided, it would be
used instead of modifying the input array. I tried this:

function add_one(in_ar, out_ar, each) 
 if (out_ar) 
 for (each in in_ar) 
 out_ar[each] = in_ar[each] + 1
 
 
 else 
 for (each in in_ar) 
 in_ar[each]++
 
 

BEGIN 
 split("1 2 3 4 5", q)
 add_one(q, z)
 print z[3]

but I get this result:

fatal: attempt to use scalar `z' as an array

There are 2 problems in your script

• the variable z isn't initialized


• the test if(out_ar) in your second code snippet is not suited for arrays

To solve the first problem, you need to assign an array element (like z[1]=1) since there is no array declaration in awk. (You can't use similar statement like declare -A as you would do in bash).

The second problem can be solved, provided you're using GNU awk, with the function isarray() or typeof().

So your code should look like this:

function add_one(in_ar, out_ar, each) 
 if (isarray(out_ar)) 
 for (each in in_ar) 
 out_ar[each] = in_ar[each] + 1
 
 
 else 
 for (each in in_ar) 
 in_ar[each]++
 
 

BEGIN 
 split("1 2 3 4 5", q)
 z[1]=1
 add_one(q, z)
 print z[3]

I recommend looking at this page and this page.