Re: [Boston.pm] Fwd: script works ok on command line, hangs when run from shell script

I'd definitely start by not using csh. It has a pile of problems as a scripting language. Especially related to pipes and file descriptors. 

http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/

-Andrew

> On Apr 27, 2017, at 11:18, Bill Ricker <[email protected]> wrote:
> 
> Apparently i replied off-list.  Here's my reply for those following along
> at home.
> 
> // Bill
> 
> ---------- Forwarded message ----------
> 
> 
> Is your interactive commandline provided by (ba)sh or [tcz]sh ?
> I see your script is Csh.
> That's one possible difference since that's where the pipe is actually
> created and sub-process spawned.
> 
> $| won't
> ​do what you want.
> 
> perldoc -v '$|'
> 
> HANDLE->autoflush( EXPR )
> $OUTPUT_AUTOFLUSH
> $|
> 
> If set to nonzero, forces a flush right away and after every write or print
> on the currently selected output channel. Default is 0 (regardless of
> whether the channel is really buffered by the system or not; $| tells you
> only whether you've asked Perl explicitly to flush after each write).
> STDOUT will typically be line buffered if output is to the terminal and
> block buffered otherwise. Setting this variable is useful primarily when
> you are outputting to a pipe or socket, such as when you are running a Perl
> program under rsh and want to see the output as it's happening. This has no
> effect on input buffering. See getc for that. See select on how to select
> the output channel. See also IO::Handle.
> 
> Mnemonic: when you want your pipes to be piping hot.
> 
> ​ If you want actual non-blocking output in an output pipe or to a file, I
> _think_ you'll need
> ​
> perldoc IO::Handle
> 
> ​*$io->blocking ( [ BOOL ] )*
> 
> If called with an argument blocking will turn on non-blocking IO if BOOL is
> false, and turn it off if BOOL is true.
> 
> blocking will return the value of the previous setting, or the current
> setting if BOOL is not given.
> 
> If an error occurs blocking will return undef and $! will be set.
> ​as in
> $io->blocking( 0 ) or croak "$!: io->blocking ( 0 )";
> 
> ​the "sub init" for SSL-capable netcat script "scnc" does :
> 
>   $SIG{INT}  = sub { $self->exit };
>   $SIG{CHLD} = 'IGNORE';
> 
>   STDOUT->blocking(0);
>   STDOUT->autoflush(1);
>   STDIN->blocking(0);
>   STDIN->autoflush(1);
> ​
> 
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