Please refer to this node: To Kill a Meme: while(defined($line = <>)).

Oopss... Seems that defined is not really needed. Thankie very muchie, Valerio! That is quite an article. I'll try to absorb it anyway. Ciao! :)

You are welcome :) Some monks here don't agree on this; read that thread and you'll discover that the real problem lies in the wrong use of defined, see Thelonius's answer for a quick answer :)

Ciao, Valerio

The idiomatic way to write that is:

local @ARGV=qw(c:/tmp.txt);
while (<>) {
    chomp;
    print "\$_: '$_'\n";
}
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And its easier to get right too. ;-)

Update after a moments reflection: My point being that no its not better to use defined, or any of the other common pieces of advice about avoiding perl idiom. The idiom exists to make your life easy and to reduce trivial and common coding errors. If you want to have to hassle with stuff like that then do it in C.

Update 2: Read the link valdez posted. ++ to him. Obviously its clear which camp im in, but I can see there are good points raised in that thread about using defined(). I still wouldnt though.

OIC, now it's clear. Yes, you're right, Have just verified everything out. chomp does return a value of 1 by default for every <> read-in. It actually ties with the contents $/. ICIC! Thanks again, Thelonius!

One further note of caution. If you use while(chomp($a = <>)), then your loop will not process the last line of the file if it is incomplete (i.e. if it is missing the final newline). It is common on DOS and Windows for the last line to be incomplete.

It is safer to put the chomp inside the body of the loop.

If you want to know if /tmp.txt has data in it use:

$qfile = "c:/tmp.txt";
if (-s $qfile) # man perlfunc has more -s = if exist with size > 0
{
  open QINPUT...
}
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while (chomp(my $qline = <QINPUT>))
{
   # yadda, yadda, yadda
}
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Though, this will fail to read the last line if it doesn't contain a newline at the end of it. (Similar to the "Incomplete last line" error vi gives you in the same situation.)

Just do what demerphq or valdez (through the link provided) suggest.

open (IN,"<" . "c:/tmp.txt") or die "Doh: $!"; # Use ()'s, and added o
+r die... sometimes that comes in hand when debugging.

while(<IN>){  # $_ is set to each line for each file.
  my $line = $_; # Take raw form of line
  $line =~ chomp $line; # chomp the line.
  if (length($line)){ # does line have non zero length?  (Sorta what y
+ou're doing.)
     print "$line\n"; 
  }
}
close IN; # Clean up.
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Well, actually this all wrong. chomp certainly doesnt belong on the right side of a =~ operator. The way to write this is to use the idiom that dragonchild outlined:

while (<$in>) {
    chomp(my $line=$_);
    next unless length $line;
    print;
}

__END__
# please excuse this stuff here, just doing some pmdev testing with th
+is node :-)
# it will be removed soon.

# No indent
 # single space
  # two spaces
   # three spaces
    # four spaces
# No indent
 # single space
  # two spaces
   # three spaces
    # four spaces
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:-)



---
demerphq


First they ignore you, then they laugh at you, then they fight you, then you win.
-- Gandhi