G'day dissident,
"This is my code:"
It's some of your code. We're left guessing at the rest.
For future reference, please supply an SSCCE.
"I found a comment on StackOverflow, saying that the UTF-8 encoding layer adds another buffering layer."
That refers to the "open pragma" (which you don't show)
not the "open function" (which you do show).
"Is this the reason why ..."
That would depend on if, and how, you used the "open pragma"
in the code you haven't shown us.
A couple of other points regarding your post:
-
You shouldn't be opening and closing the logfile on every call to printtolog().
-
Already mentioned by ++swl.
-
See how I handle this in the code below.
-
:encoding(UTF-8) is preferred over :utf8.
"Does there exist a way to circumvent this buffering and to force creation and flushing of the file at all?"
That emboldened text looks like you're shouting (at us).
After "trying unsuccessfully half the day" I can understand that you're frustrated;
please don't take it out on your fellow monks — we're here to help, not to be abused. Thankyou.
With missing code, I am guessing somewhat;
however, I think the following annotated script should be sufficient for you to resolve your problem.
#!/usr/bin/env perl
use strict;
use warnings;
use autodie;
use utf8;
use constant DELAY => 2;
my @ascii_texts = map "text#$_", 0 .. 9;
my @unicode_texts = map "🅃🄴🅇🅃#️
+$_", qw{0️ 1️ 2️ 3️ 4️ 5️ 6
+️ 7️ 8️ 9️};
for my $i (0 .. 9) {
write_ascii_log($ascii_texts[$i]);
write_unicode_log($unicode_texts[$i]);
sleep DELAY;
}
close_ascii_log();
close_unicode_log();
sub now {
return scalar localtime();
}
# Log file routines
# Note anonymous block
{
my ($asc_filename, $uni_filename);
BEGIN {
($asc_filename, $uni_filename) = qw{ascii.log unicode.log};
}
my ($ascii_fh, $unicode_fh);
sub _open_asc {
open $ascii_fh, '>>', $asc_filename;
$ascii_fh->autoflush();
# For demo only:
print "Run 'tail -f $asc_filename' in a separate window.\n";
print 'Hit <Enter> when ready: ';
(undef) = scalar <STDIN>;
return;
}
sub write_ascii_log {
my ($text) = @_;
_open_asc() unless defined $ascii_fh;
$ascii_fh->print(now(), ": $text\n");
return;
}
sub close_ascii_log {
return unless defined $ascii_fh;
undef $ascii_fh;
# For demo only:
print "Stop 'tail -f $asc_filename'.\n";
print 'Hit <Enter> when ready: ';
(undef) = scalar <STDIN>;
return;
}
sub _open_uni {
open $unicode_fh, '>>:encoding(UTF-8)', $uni_filename;
$unicode_fh->autoflush();
# For demo only:
print "Run 'tail -f $uni_filename' in a separate window.\n";
print 'Hit <Enter> when ready: ';
(undef) = scalar <STDIN>;
return;
}
sub write_unicode_log {
my ($text) = @_;
_open_uni() unless defined $unicode_fh;
$unicode_fh->print(now(), ": $text\n");
return;
}
sub close_unicode_log {
return unless defined $unicode_fh;
undef $unicode_fh;
# For demo only:
print "Stop 'tail -f $uni_filename'.\n";
print 'Hit <Enter> when ready: ';
(undef) = scalar <STDIN>;
return;
}
}
In case the line with Unicode text is rendered as entity references,
here it is in a <pre> block:
my @unicode_texts = map "🅃🄴🅇🅃#️$_", qw{0️ 1️ 2️ 3️ 4️ 5️ 6️ 7️ 8️ 9️};
Here's a sample run:
ken@titan ~/tmp/pm_11154936_buffering
$ ./log_example1.pl
Run 'tail -f ascii.log' in a separate window.
Hit <Enter> when ready:
Run 'tail -f unicode.log' in a separate window.
Hit <Enter> when ready:
Stop 'tail -f ascii.log'.
Hit <Enter> when ready:
Stop 'tail -f unicode.log'.
Hit <Enter> when ready:
ken@titan ~/tmp/pm_11154936_buffering
$
Here's the output from tailing ascii.log:
ken@titan ~/tmp/pm_11154936_buffering
$ tail -f ascii.log
Fri Oct 13 23:07:47 2023: text#0
Fri Oct 13 23:08:07 2023: text#1
Fri Oct 13 23:08:09 2023: text#2
Fri Oct 13 23:08:11 2023: text#3
Fri Oct 13 23:08:13 2023: text#4
Fri Oct 13 23:08:15 2023: text#5
Fri Oct 13 23:08:17 2023: text#6
Fri Oct 13 23:08:19 2023: text#7
Fri Oct 13 23:08:21 2023: text#8
Fri Oct 13 23:08:23 2023: text#9
Here's the output from tailing unicode.log:
ken@titan ~/tmp/pm_11154936_buffering
$ tail -f unicode.log
Fri Oct 13 23:08:05 2023: 🅃🄴🅇🅃#️0️
Fri Oct 13 23:08:07 2023: 🅃🄴🅇🅃#️1️
Fri Oct 13 23:08:09 2023: 🅃🄴🅇🅃#️2️
Fri Oct 13 23:08:11 2023: 🅃🄴🅇🅃#️3️
Fri Oct 13 23:08:13 2023: 🅃🄴🅇🅃#️4️
Fri Oct 13 23:08:15 2023: 🅃🄴🅇🅃#️5️
Fri Oct 13 23:08:17 2023: 🅃🄴🅇🅃#️6️
Fri Oct 13 23:08:19 2023: 🅃🄴🅇🅃#️7️
Fri Oct 13 23:08:21 2023: 🅃🄴🅇🅃#️8️
Fri Oct 13 23:08:23 2023: 🅃🄴🅇🅃#️9️
Obviously, you'll need to run that yourself to see that the lines are printed to the logs every two seconds;
you don't have to wait until filehandles are closed or the script ends.
See also: "Suffering from Buffering?".
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