awk provides one-dimensional associative arrays
(arrays indexed by string values). All arrays are associative; numeric
indices are converted automatically to strings.
- Array elements are referenced as
Referencing an element creates it if it did not exist previously.
- The proper way to see if an array has an element with a given index
is to use the
in operator: ‘indx in array’.
- Use ‘for (indx in array) …’ to scan through all the
individual elements of an array. In the body of the loop, indx takes
on the value of each element’s index in turn.
- The order in which a ‘for (indx in array)’ loop
traverses an array is undefined in POSIX
awk and varies among
gawk lets you control the order by assigning
special predefined values to
- Use ‘delete array[indx]’ to delete an individual element.
To delete all of the elements in an array,
use ‘delete array’.
This latter feature has been a common extension for many
years and is now standard, but may not be supported by all commercial
awk simulates multidimensional arrays by separating
subscript values with commas. The values are concatenated into a
single string, separated by the value of
SUBSEP. The fact
that such a subscript was created in this way is not retained; thus,
SUBSEP may have unexpected consequences. You can use
‘(sub1, sub2, …) in array’ to see if such
a multidimensional subscript exists in array.
gawk provides true arrays of arrays. You use a separate
set of square brackets for each dimension in such an array:
data[row][col], for example. Array elements may thus be either
scalar values (number or string) or other arrays.
- Use the
isarray() built-in function to determine if an array
element is itself a subarray.