printf in if-statement

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

Hello monks, I have a question/problem concerning a printf in an if-statement. In the following code I am going through a file with data in time. Some of this data is worthless which is represented by a file holding the start and endtimes of these worthless timespans in epoch seconds($gapsfile). For each day I want to calculate the number of gaps as well and print these to file. However for some reason the printf in the if-statement which checks if a next day begins ( if(! ($julday == $julday_old)) ) does not work. It does print to filehandle OUT1 before the if statement. The print statements, printing the same variables to standard output in the if-statement do function as well. I am confused.....?? thanks in advance!

my $error_cnt = 0;
my $day_cnt = 0;
my $month = 0;
my $test;
my $julday_old;
open(OUT,">$resultsfile.corrected");
open(OUT1,">$resultsfile.gaps");
open(INP, $resultsfile);
while (<INP>){
  chomp($_);
  my $line = $_;
  my ($timestr,$timebin,$fish,$vel,$azi,$px,$py) = split(/\s+/,$line);
  my ($year,$julday,$hour,$min,$sec,$msec) = split(/\./,$timestr);
  my $timest = timegm_nocheck($sec,$min,$hour,$julday,$month,$year);
  my $timeend = $timest + 512;
  $julday_old = $julday if $. == 1;
  #$test = sprintf"%s %s\n",$julday_old,$day_cnt if $. != 1;
  #printf OUT1 "%s",$test;
  if(! ($julday == $julday_old)){
    printf OUT1 "%s %s\n",$julday_old,$day_cnt;
    print "$julday_old  ";
    print "$day_cnt\n";
    $julday_old = $julday;
    $day_cnt = 0;
  }
  open(IN,"$gapsfile");
  while (<IN>){
    chomp($_);
    my ($sttime,$endtime) = split(/\s+/,$_);
    if ($sttime < $timest && $endtime > $timeend){
      print "Timespan $timestr will be removed\n";
        $day_cnt++;
        $error_cnt++;
        last;
    }
    elsif ($endtime > $timest+3.2 && $endtime < $timeend){
      print "Timespan $timestr will be removed\n";
      $day_cnt++;
      $error_cnt++;
      last;
    }
    elsif ($sttime+3.2 < $timeend && $sttime > $timest){
      print "Timespan $timestr will be removed\n";
      $day_cnt++;
      $error_cnt++;
      last;
    }
    else{
      printf OUT "$line\n";
    }
  }
  close(IN);
}
close(OUT);                                                           
+ close(OUT1);
print "\n\nTotal number of timespans of 8m 32s removed is: $error_cnt\
+n";
close(INP);
[download]

Comment on printf in if-statement Select or Download Code

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Re: printf in if-statement by toolic (Bishop) on Apr 21, 2009 at 13:48 UTC
Without a small sample of your input file, it is not simple to reproduce your results. Try to print both values before your "if" line: `print "julday >>>$julday<<<\n"; print "julday_old >>>$julday_old<<<\n";` [download] Are these values integers, or are they floating point values? Isn't... `if(! ($julday == $julday_old)){` [download] the same as...? `if ($julday != $julday_old){` [download]	[reply] [d/l] [select]
Re: printf in if-statement by lostjimmy (Chaplain) on Apr 21, 2009 at 13:55 UTC
Nothing jumps out at me as being wrong in your code, but I do have some stylistic things and best practices you might want to consider... You should really be checking the success of your open calls. Also, most people will suggest the three argument form of `open` and lexical file handles: `open my $out, ">", "$resultsfile.corrected" or die "could not open $resultsfile.corrected: $!"` You don't need to use `printf` at all in this code. Using `print` and string interpolation is usually easier to read: `print $out1 "$julday_old $day_cnt\n"` I think that `if (! ($julday == $julday_old))` would be better written as `if ($julday != $julday_old)` OK, enough of my opinions. ~~So the only real question I have is, are you sure that block of code is being reached? I assume you're seeing the printouts to the console, but I just thought I would ask.~~ Update: I reread the question and saw that the prints are showing up on stdout. I'm out of ideas...	[reply] [d/l] [select]
Re^2: printf in if-statement by Utrecht (Novice) on Apr 21, 2009 at 14:21 UTC
Hi, thank you for your input. I am sorry I was bothering you, because I think I was a little too hasty with my question. For some reason, the print-statement is not executed realtime, but only after the while over filehandle INP is finished. I don't understand why this buffering occurs in this case as normally it doesn't, but the code works fine anyway.	[reply]
Re^3: printf in if-statement by almut (Canon) on Apr 21, 2009 at 14:49 UTC
I don't understand why this buffering occurs in this case as normally it doesn't I'd say it's the other way around: buffering is the default behaviour. Only under certain circumstances, the behaviour is changed, for example when the handle is connected to a terminal (like STDOUT, typically). In this case, line-buffering (as opposed to block-buffering) is used, because an interactive mode of operation is assumed. You could enable auto-flushing, though (on any handle): `use IO::Handle; open my $fh, ">", "test.out" or die $!; $fh->autoflush(); print $fh "..."; # is being written immediately` [download] (see also Re: Troubles with do...while loop and sleep (line- vs. block-buffered))	[reply] [d/l]
Re: printf in if-statement by ikegami (Patriarch) on Apr 21, 2009 at 13:59 UTC
Then why don't you check for errors! Starting with `open`. (Too slow! See Re: printf in if-statement)	[reply] [d/l]