try scalar(<STDIN>)
On Wed, Dec 15, 2010 at 3:05 PM, Assaf Gordon <gor...@cshl.edu> wrote:
> Hello all,
>
> Perhaps you could help me with some perl weirdness (or my lack of
> understanding)...
>
> My goal is to have a tiny perl program, that reads STDIN, grabs couple of
> lines from it, then executes another program which should consume the rest
> of the lines from STDIN.
>
> This works as expected when using shell redirection, but not when using
> pipes.
>
> I've tried it on two different systems (Debian with perl 5.10.1 and CentOS
> with perl 5.8.8).
>
> Complete details below.
> Any suggestions will be very welcomed.
>
> Thanks,
> -Assaf
>
> =======
>
> $ cat input.txt
> A
> B
> C
> D
>
> ### The first program does nothing but run "sort"
> $ cat test_good.pl
> #!/usr/bin/perl
> system("sort");
>
> ### Redirection works
> $ ./test_good.pl < input.txt
> A
> B
> C
> D
>
> ### Pipes work
> $ cat input.txt | ./test_good.pl
> A
> B
> C
> D
>
>
> ### The second program reads one line from STDIN, then runs "sort"
> $ cat test_bad.pl
> #!/usr/bin/perl
> $dummy = <STDIN>;
> system("sort");
>
> ### Redirection still works (first line removed)
> $ ./test_bad.pl < input.txt
> B
> C
> D
>
> ### Pipes do not work - why ???
> $ cat input.txt | ./test_bad.pl
> ## nothing is printed
>
> ==================
>
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>
--
Tzadik
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