Re: avoid errors when printing to socket

On Thursday, September 30, 2021 9:30:01 PM CEST Andy Bach wrote:
> > https://perldoc.perl.org/functions/print says that 'print' would return
> 
> true
> 
> > if successful and doesn't say what it returns otherwise.  It also says
> 
> that
> 
> > "Printing to a closed pipe or socket will generate a SIGPIPE signal."
> 
> Looks like print returns 1 if it succeeds, undef if not:
> $ perl -wE 'my $res = print "hi mom\n"; say $res'
> hi mom
> 1
> $ perl -wE 'my $res = print OUT "hi mom\n"; say $res'
> Name "main::OUT" used only once: possible typo at -e line 1.
> print() on unopened filehandle OUT at -e line 1.
> Use of uninitialized value $res in say at -e line 1.
> $ perl -E 'open(OUT, ">", STDERR) ;my $res = print OUT "hi mom\n"; say $res'
> 1
> $ perl -wE 'open(OUT, ">", STDERR); close OUT ;my $res = print OUT "hi
> mom\n"; say $res'
> print() on closed filehandle OUT at -e line 1.
> Use of uninitialized value $res in say at -e line 1.
> 
> >So I tried to install a signal handler, but either I did that wrong, or no
> 
> signal was generated.  What can I do?
> 
> Well, seeing a SIGPIPE would mean it's failed already, so it's not going to
> get you any further. Showing your code might help in debugging.

If the signal would be caught, I could handle the error and try to reconnect, 
or, if that also fails, do something else.

The source is here:


https://www.adminart.net/Relaiscontrol.pm.html
https://www.adminart.net/Relaiscontrol.pm.gz


It's for controlling this relais: https://www.adminart.net/Relaiscontrol.pm.gz

It works fine, I just would like to add some more error handling.




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