Re: [bug-gawk] gawk 4.1.3 gensub() warning

[Ed Morton]

see my response below

On 9/3/2015 7:34 AM, address@hidden wrote:
> Ed Morton <address@hidden> wrote:
>
> > I'm seeing this new warning in gawk 4.1.3 executing existing scripts:
> >
> > $ echo 'a' | gawk '{print gensub(/a/,"b","")}'
> > gawk: cmd. line:1: (FILENAME=- FNR=1) warning: gensub: third argument `' treated
> > as 1
> > b
> >
> > This will impact a ton of scripts, like if sed suddenly started issuing warnings
> > if you wrote `s/foo/bar/` instead of `s/foo/bar/1`. Is it here to stay?
> >
> >       Ed.
> The warning is indeed here to stay. Use of "" is wrong; you should
> supply a numeric 1 there.  Fix your scripts.
>
> Arnold
Arnold - there's lots of things that are "wrong" but harmless so gawk just 
handles them sensibly without issuing warnings. For example, using an out of 
range starting index for substr():

$ awk 'BEGIN{print substr("foobar",-127,3)}'
foo

$ awk 'BEGIN{print substr("foobar","",3)}'
foo

is IMHO much more likely to indicate a real problem in your code than using "" 
instead of 1 in gensub() but in substr() gawk just quietly assumes you meant to 
use 1 instead of -127 or "" or whatever value a loop variable accidentally 
became. If substr() can continue to quietly assume that anything numerically 
less than 1 means 1, why can't gensub() continue to do that too after all of 
these years of doing so?

Anyway, I've changed 130+ scripts on one machine now, hoping I didn't screw any 
of them up, and moving on to my next machine so I'm far enough along the process 
of updating my scripts that I'll finish the rest and so I'm fine either way.

Thanks for the quick response.

    Ed.