An important aspect to remember about arrays is that array subscripts
are always strings. When a numeric value is used as a subscript,
it is converted to a string value before being used for subscripting
(see section Conversion of Strings and Numbers).
This means that the value of the predefined variable
affect how your program accesses elements of an array. For example:
xyz = 12.153 data[xyz] = 1 CONVFMT = "%2.2f" if (xyz in data) printf "%s is in data\n", xyz else printf "%s is not in data\n", xyz
This prints ‘12.15 is not in data’. The first statement gives
xyz a numeric value. Assigning to
data with the string value
(using the default conversion value of
Thus, the array element
data["12.153"] is assigned the value one.
The program then changes
the value of
CONVFMT. The test ‘(xyz in data)’ generates a new
string value from
"12.15"—because the value of
CONVFMT only allows two significant digits. This test fails,
"12.15" is different from
According to the rules for conversions
(see section Conversion of Strings and Numbers), integer
values always convert to strings as integers, no matter what the
CONVFMT may happen to be. So the usual case of
the following works:
for (i = 1; i <= maxsub; i++) do something with array[i]
The “integer values always convert to strings as integers” rule
has an additional consequence for array indexing.
Octal and hexadecimal constants
(see section Octal and Hexadecimal Numbers)
are converted internally into numbers, and their original form
is forgotten. This means, for example, that
array[0x11] all refer to the same element!
As with many things in
awk, the majority of the time
things work as you would expect them to. But it is useful to have a precise
knowledge of the actual rules, as they can sometimes have a subtle
effect on your programs.