read through \x0a in data piped via STDIN

How09 has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I am trying to read data piped to the program via stdin.
It seems that an \x0a in the data will end what is taken as "<STDIN>".
Other "control" characters will go into STDIN ok and the buffer behaves as expected.
----- small example code -----

#!/usr/bin/perl -wT
use strict;
use warnings;

my $s1 = <STDIN>;
print("\$s1= <$s1> \n");

if (<STDIN>) { 
  my $s2 = <STDIN>;
  print("\$s2= <$s1> \n"); 
};
[download]

----- some output samples: ----- (linux-gnome terminal)


perl>  echo -ne "hello\x0aWorld" | ./pipe_x-1.pl  # try \n
$s1= <hello
> 
$s2= <hello:
> 

perl>  echo -ne "hello\x0dWorld" | ./pipe_x-1.pl  # try \r
World> ello

perl>  echo -ne "hello\x09World" | ./pipe_x-1.pl  # try \t
$s1= <hello     World>
[download]

As you can see the samples using 0x0d and 0x09 are read through to EOF and buffer is empty so the $s2 print does not occur.

But something wierd happens with the 0x0a.
Very interesting , what can I do to read through that?

Comment on read through \x0a in data piped via STDIN Select or Download Code

Replies are listed 'Best First'.
Re: read through \x0a in data piped via STDIN by mr_mischief (Monsignor) on Dec 09, 2010 at 17:54 UTC
You're not reading to EOF. This: `my $s1 = <STDIN>;` [download] reads exactly one line. Since `$/` is "\n" (see perlvar), your line ends at "\n". If you want to read by line and get more than one line, I suggest some sort of iteration. Perhaps a `while` loop. The most common idiom for reading a whole file line by line in Perl is: `while ( <$filehandle> ) { # do something }` [download] In your case, that'd be: `while ( <STDIN> ) { # do something }` [download] There's really nothing mysterious going on. All of this is well-documented and widely known.	[reply] [d/l] [select]
Re: read through \x0a in data piped via STDIN by VinsWorldcom (Prior) on Dec 09, 2010 at 17:56 UTC
Try adding: `$/ = undef;` [download] after your 'use' statements: `#!/usr/bin/perl use strict; use warnings; $/ = undef; my $s1 = <STDIN>; print("\$s1= <$s1> \n"); if (<STDIN>) { my $s2 = <STDIN>; print("\$s2= <$s1> \n") }` [download] By not defining (undef) the input record separator (default newline), it will read to EOF.	[reply] [d/l] [select]
Re^2: read through \x0a in data piped via STDIN by How09 (Novice) on Dec 09, 2010 at 18:23 UTC
Oh I see. It all make sense now. perlvar - tonight! Thank you all.	[reply]
Re: read through \x0a in data piped via STDIN by Anonyrnous Monk (Hermit) on Dec 09, 2010 at 17:54 UTC
But something wierd happens with the 0x0a Well, `<...>`, aka readline, by definition reads up to the next input record separator, which by default is a newline, i.e. `\n` or `0x0a`. You could change `$/` ...	[reply] [d/l] [select]