If Net::Ping gets failure and has the special statement for the failure,
how can return this statement to the caller?
Thank you.
On Fri, Nov 1, 2019 at 5:30 AM Andy Bach <afb...@gmail.com> wrote:
> > How do I let the caller know what happens when the method fails to run?
>
> As noted, die() ends the program at that point, sending the text to stderr
> and setting an exit code to the shell. If you want your subs are to
> communicate with their calling code, you can use the return values to show
> success or failure:
> sub mytest {
>
> my $host = shift;
> my $p = Net::Ping->new();
> unless ($p->ping($host)) {
> $p->close();
> return 0;
> }
> return 1;
> }
>
> my $host = 'www.google.com';
> if ( not A::mytest($host) ) {
> print "failed to ping: $host\n";
> }
> else {
> print "$host is alive\n";
> }
>
> The choice of returning one or zero is up to you (or anything else - a
> range of values for different failures), just needs to be agreed on ahead
> of time. You can do something like try/catch blocks around code that dies
> by using "eval", something like:
> package main;
>
> eval {
> A::mytest('www.google.com');
> };
> if ( $@ ) {
> print "A::mytest died, saying $@\n";
> }
>
> The Perl var "$@" gets what ever the called code might have sent to
> stderr, e.g.:
> $ test_net_ping.pl
> A::mytest died, saying can't ping www.google.com at /usr/local/bin/
> test_net_ping.pl line 14.
>
> Just to note, as a package test, normally, your package A and B would be
> separate scripts (say Apingtest.pm and Bpingtest.pm, in the @INC path)
> and the main code would just have
> #!/usr/bin/perl
> use Apingtest;
> use Bpingtest;
> use strict;
> use warnings;
> ...
>
> On Thu, Oct 31, 2019 at 4:42 AM Maggie Q Roth <rot...@gmail.com> wrote:
>
>> Hello
>>
>> Sorry I am new to perl, I was reading the charter about package.
>>
>> I tried to write the code below:
>>
>> use strict;
>> use Net::Ping;
>>
>> package A;
>>
>> sub mytest {
>>
>> my $host = shift;
>> my $p = Net::Ping->new();
>> unless ($p->ping($host)) {
>> $p->close();
>> die "can't ping $host";
>> }
>> }
>>
>> 1;
>>
>> package B;
>>
>> sub mytest {
>>
>> my $host = shift;
>> my $p = Net::Ping->new();
>> unless ($p->ping($host)) {
>> $p->close();
>> return 0;
>> }
>> }
>>
>> 1;
>>
>> package main;
>>
>> A::mytest('www.google.com');
>>
>> print B::mytest('www.google.com');
>>
>>
>>
>> When I run it, always get:
>> $ perl test.pl
>> can't ping www.google.com at test.pl line 12.
>>
>>
>> Shouldn't I return die() in package's method?
>> How do I let the caller know what happens when the method fails to run?
>>
>> Thanks in advance.
>>
>> Yours
>> Maggie
>>
>
>
> --
>
> a
>
> Andy Bach,
> afb...@gmail.com
> 608 658-1890 cell
> 608 261-5738 wk
>
