Re: substr() - copying or not copying, that is here the question.

In article <101f9oo$18edp$1@dont-email.me>,
Janis Papanagnou  <janis_papanagnou+ng@hotmail.com> wrote:

In the context   p=index(substr(t,s),r)
it would not be necessary to copy the substr(t,s),
the index() function could operate on the original
using some access "descriptor" (say, a pointer and
a length) in read-only mode.
>
Will (GNU) Awk do a copy of the data value or does
it use a read-only descriptor access to the already
existing substring of variable "t"?
>
Currently I'm playing with some huge data and copies
of MB sized data is costly (if it's repeatedly done
with various substr() subscripts).

substr() makes a copy. This is clear in the code.

It's almost impossible to do this via read-only descriptor.
Consider something like

x = substr($0, 10, 15)
getline
print x

Gawk manages the storage such that for something like
your example the copy will be released after index()
returns a value.