comment on

I have been experiencing some odd behaviour that I've tracked down to a print statement (I think). Essentially, the print statement (I/O buffer?) doesn't output specific lines. Every line after the first line in fact although it always prints the first line. When run against different data sets, the loop will not drop lines consistently from set to set but will consistently drop data from the same data set on multiple runs.

The data is output to file if a filename is specified on the command line and to STDOUT if no filename is given.

The problem seems to occur only when I specify the file name on the command line. It does not occur if when printing to STDOUT. I can also correctly redirect the output from STDOUT into a file.

I've tried ...

setting $| ($AUTOFLUSH) to true.
hard coding file names and all the other variables
checking for Ctrl-Z or other non-printable chars in data
Output to both STDOUT and file. The loop will output all the expected records to STDOUT while, at the same time, only printing the first record to file.
running the program directly on the server (the output file is on a shared drive)
running the program under a different OS on different machines

Additional info & suggestions from various monks ...

The debugger shows everything is OK. Results from debugger are, however, same as from cmd line
The loop will retrieve and process all of the records it is supposed to
$obstr is set to each record and appears correctly formatted after the join
the return value for print is TRUE for all records
use strict; use warnings; use diagnostics; are set
using syswrite with the same results as print
corrected buffer AUTOFLUSH to actually flush the file buffer vice STDOUT

System specs ...

The data is standard ASCII (not utf8) data. A check on the raw data does not turn up any untoward characters.
The database connection is Win32::ODBC
The system is Activestate Perl 5.6.1 build 635 on WinXP and Win 2000

Relevent code

if($db01->FetchRow()){
    open my $fh,">",$cfg->{outfile} if(defined($cfg->{outfile}));
    unless($fh){
        warn "Unable to open output file $cfg->{outfile}\n$!\nUsing ST
+DOUT\n" if(defined($cfg->{outfile}));
        $usestdout = TRUE;
        $fh = \*STDOUT;
    }
    do{
        ++$recnum;
        printf("\b\b\b\b\b\b\b\b\b%-9s",$recnum) if($cfg->{displaycoun
+t});
        @obrec = $db01->Data();
        $obrec[$_] = sprintf("%-*s",$oblen03[$_],($obrec[$_] || '')) f
+oreach (0..$#obrec);
        $obstr = join("\t",@obrec);

# some troubleshooting attempts
#        print STDOUT "$obstr\n" if($obstr =~ /[[:cntrl:]]+/); #checki
+ng for control chars in rec
#        print STDOUT "$obstr\n" if($obstr =~ /[[:^print:]]+/); #check
+ing for unprintable chars in rec
#        print STDOUT "$obstr\n";

         print $fh "$obstr\n";
    }while($db01->FetchRow());
    close($fh) unless($usestdout);
}
[download]

At this point, I'm stumped. Any suggestions will be most appreciated.

Update01: added some additional info and the results of some monk suggestions.

Update02: I solved it. Read operator error :o( Under certain circumstances, the program makes a a second pass through the loop. The open statement then clobbers the file and only inputs a portion of the remaining records. The open mode should be append ">>" not create ">". Thanks for all the great suggestions though. I learned a few things.

PJ
use strict; use warnings; use diagnostics;

In reply to Odd behaviour from print statement by periapt

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		`&`
	<		`<`
	>		`>`
	[		`[`
	]		`]`

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.