Re: difference in RS handling for equivalent regexps with unending input stream

[Ed Morton]

Thanks Andy but unfortunately I'm not able to install any extensions 
such as the "select" library that don't just come with the gawk 
installation on my work computer (where I most need to develop/use 
solutions to problems) and so I avoid doing so on my personal one too to 
keep the tools I use on both as similar as possible. So I won't be able 
to try your suggestion.

    Ed.

On 7/3/2024 12:22 PM, Andrew J. Schorr wrote:
> On Wed, Jul 03, 2024 at 06:58:27AM -0500, Ed Morton wrote:
> > I'd be interested to hear if you or anyone else reading this knows
> > of a way to read the input 1 char at a time in a case like this
> > where the input is unending and we can't rely on a regexp match for
> > RS to find each character.
> Have you considered trying to use the select extension and its
> nonblocking feature?
>
> Something like this sort of seems to work:
>
> (echo "A;B;C;D;"; cat -) | gawk -v 'RS=[;=]' -lselect -ltime '
> BEGIN {
>     fd = input_fd("")
>     set_non_blocking(fd)
>     PROCINFO[FILENAME, "RETRY"] = 1
>     while (1) {
>        delete readfds
>        readfds[fd] = ""
>        select(readfds, writefds, exceptfds)
>        while ((rc = getline x) > 0) {
>          if (rc > 0)
>             printf "%d [%s]\n", ++n, x
>          else if (rc != 2) {
>             print "Error: non-retry error"
>             exit 1
>          }
>        }
>     }
> }'
>
> Regards,
> Andy