On 8/13/07, Jeff Pang <[EMAIL PROTECTED]> wrote:
>
>
> -----Original Message-----
> >From: [EMAIL PROTECTED]
> >Sent: Aug 14, 2007 3:20 AM
> >To: beginners@perl.org
> >Subject: piping and reading stdin
> >
> >I want to read from a pipe in my perl script invoked like:
> >
> >date | perl myperlscript.pl
> >
> >I understand that this puts the text outputted from the date program
> >into the stdin. How could I check the buffer contained by the stdin
> >without it blocking for you to input anything from the keyboard if
> >nothing was piped in to the command.
> >
> >my perlscript contains something like:
> >
> >#this part im unsure about so im using functions that dont exist
> >if(buffer_has_stuff_in_it(STDIN)){
> > while(<STDIN>){
> > print "$_\n";
> > }
> >}
> >else{
> > print "You didnt pipe anything into this program!\n";
> >}
> >
>
> Hi,
>
> You need an IO::Select object to be monitored,if it's timeouted,then die or
> exit.
> Just show my sample codes,hope this helps.
>
> use strict;
> use IO::Select;
>
> my $timeout=1; # wait for 1 second
>
> open PIPE,'cat|' or die $!; # since 'cat' doesn't input anything,program
> would die after 1 sec.
> my $oldhd=select PIPE;$|++;select $oldhd;
> my $s = IO::Select->new();
> $s->add(\*PIPE);
> if (my @ready = $s->can_read($timeout)) {
> my @content=<PIPE>;
> print @content;
> }else {
> die "no input\n";
> }
> close PIPE;
snip
Another method is to use turn off blocking for STDIN. The following
code should be run like this
perl script.pl send | perl script.pl
#!/usr/bin/perl
use strict;
use warnings;
use IO::File;
if (defined $ARGV[0] and $ARGV[0] eq 'send') {
STDOUT->autoflush(1);
for my $i (1 .. 10) {
print "sending $i\n";
sleep 3;
}
exit;
}
STDIN->blocking(0);
my $timeout = 10;
my $timer;
while (1) {
last if $timer++ > $timeout;
local $_ = <STDIN>;
if (defined) {
print;
$timer = 0;
}
sleep 1;
print localtime() ."\n";
}
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