Re^2: <> oddity ?

[Krambambuli]

As expected... hmm. Define a sample.txt like

1
2
3

And then run $ test.pl sample.txt

where test.pl is

#!/usr/bin/perl

use strict;
use warnings;

my $i = 0;
while (<>) {
    print $_;
    last if ++$i >= 2;
}

my $line;
print "My extra line: $line" while $line = <>;

Why would this program then NOT wait for any further input via STDIN ?

[LanX]

> Why would this program then NOT wait for any further input via STDIN ?

Perl can't read your mind, if you want to read from STDIN, explicitly use STDIN instead of stretching DWIM magic behavior till it breaks.

UPDATE:

actually your example is reading from STDIN, but maybe you should stop the redirecting from file to STDIN if you wanna read from interactive input (keyboard).

see select

[Krambambuli]

Just to clarify:

wishing to deal with various use modes in a perfectly similar manner, I wanted to have 3 distinct modes of calling the program behaving absolutely similar, with minimum fuss about that in the code:

$ test.pl sample.txt sample1.txt ... sampleN.txt
$ test.pl <sample.txt
$ cat sample.txt sample1.txt ... sampleN.txt | test.pl

All is well with this with the use of <>, except the fact that once EOF is seen, no further attempt to read from <> is allowed - or STDIN is opened, and will wait forever if you're unaware of it...

Thanks you helping to sort this out.

UPDATE As perlop says in 'I/O Operators':

The <> symbol will return "undef" for end-of-file only once. If you call it again after this, it will assume you are processing another @ARGV list, and if you haven't set @ARGV, will read input from STDIN.

Now I know :)

[Krambambuli]

OK, got it solved and understood now, thanks.

I actually just want NOT to read from STDIN when there is a file given in the command line, and stop reading when that file is exhausted.

Turns out that I should NOT any further $line = <> once that hit EOF, because the immediate next attempt to do so will just open STDIN.

Ahaa... :)

Thank you.