Arrays of Arrays, described how gawk
provides arrays of arrays. In particular, any element of
an array may be either a scalar, or another array. The
isarray()
function (see Type Functions)
lets you distinguish an array
from a scalar.
The following function, walk_array()
, recursively traverses
an array, printing each element's indices and value.
You call it with the array and a string representing the name
of the array:
function walk_array(arr, name, i) { for (i in arr) { if (isarray(arr[i])) walk_array(arr[i], (name "[" i "]")) else printf("%s[%s] = %s\n", name, i, arr[i]) } }
It works by looping over each element of the array. If any given element is itself an array, the function calls itself recursively, passing the subarray and a new string representing the current index. Otherwise, the function simply prints the element's name, index, and value. Here is a main program to demonstrate:
BEGIN { a[1] = 1 a[2][1] = 21 a[2][2] = 22 a[3] = 3 a[4][1][1] = 411 a[4][2] = 42 walk_array(a, "a") }
When run, the program produces the following output:
$ gawk -f walk_array.awk -| a[4][1][1] = 411 -| a[4][2] = 42 -| a[1] = 1 -| a[2][1] = 21 -| a[2][2] = 22 -| a[3] = 3