Re: [bug-gawk] Index function problem

[Davide Brini]

On Sun, 21 Apr 2013 08:06:33 +0100, Christopher Durant
<address@hidden> wrote:

> I notice that if you use a regular expression as the second parameter in
> an index call e.g. index ($0, /[A-Z]/); it is allowed but gives
> unpredictable results.  Perhaps this usage should be flagged as an error.

awk converts /[A-Z]/ into 1 or 0 depending on whether $0 matches the
pattern. This number is then converted into a string, which is what index()
expect.

See these examples:

# this is like doing index($0, "0")
$ echo 'aBCD' | awk '{ print index($0, /[A-Z]/) }'
0

# this is like doing index($0, "1")
$ echo 'aB1D' | awk '{ print index($0, /[A-Z]/) }'
3


To do what you're likely trying to do, you need to use match() and the
special variables RSTART and RLENGTH. See the man for the details.

-- 
D.