in reply to Re: Why can't I write to a custom log from a Catalyst application on SELinux/CentOS
in thread Why can't I write to a custom log from a Catalyst application on SELinux/CentOS

> close LOG;

Hm ... I already mentioned $|

https://perldoc.perl.org/perlvar#$OUTPUT_AUTOFLUSH

Though the documentation says

> forces a flush right away and after every write or print on the currently selected output channel.

so, this means one has to select LOG before using it???°

IO::Handle mentions a method autoflush

BUT from my experience are opened handles per default unbuffered???

Or are they only line-buffered, and the OP forgot the trailing "\n"?

°) and after some digging I found this in the FAQ

{
    my $previous_default = select(STDOUT);  # save previous default
    $|++;                                   # autoflush STDOUT
    select(STDERR);
    $|++;                                   # autoflush STDERR, to be 
+sure
    select($previous_default);              # restore previous default
}

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

Replies are listed 'Best First'.
Re^3: Why can't I write to a custom log from a Catalyst application on SELinux/CentOS
by LanX (Saint) on Feb 11, 2021 at 17:41 UTC
    > Or are they only line-buffered, and the OP forgot the trailing "\n"?

    Nope, from testing in the debugger, do new handles automatically autoflush

      DB<280> open LOG, ">>", "log.txt"

  DB<281> ! type log.txt
  DB<282> print LOG "bla"

  DB<283> ! type log.txt
bla  DB<284>

  DB<284> print LOG "\n"

  DB<285> ! type log.txt
bla
  DB<286>

    [download]

    probably is Catalyst bending the defaults?

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery

[reply]
[d/l]
      Not sure about the debugger, but code shows otherwise: 
      #!/usr/bin/perl
use strict;
use warnings;
use feature qw{ say };

open OUT, '>', 'log.txt' or die $!;
print OUT "bla\n";

open IN, '<', 'log.txt' or die $!;
my $nothing = <IN>;
say "Read: $nothing.\n";

close OUT;
my $bla = <IN>;
say "Read: $bla.\n";

      [download]
      map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
[reply]
[d/l]
[select]
        so yes, autoflush is not default, but you don't need to close after explicitly setting it

        #!/usr/bin/perl
use strict;
use warnings;
use feature qw{ say };

unlink "./log.txt" or warn "$!";         # in case


open OUT, '>>', 'log.txt' or die $!;

{
    my $previous_default = select(OUT);  # save previous default
    $|++;                                # autoflush OUT
    select($previous_default);           # restore previous default
}

print OUT "before close";

open IN, '<', 'log.txt' or die $!;

my $read;

$read = <IN>;
chomp $read;
say "Before close: <$read>";

close OUT;

        [download]

        Before close: <before close>

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        Wikisyntax for the Monastery

[reply]
[d/l]
[select]
        > Not sure about the debugger, but code shows otherwise:

        It's not the debugger, I think the system command (aka backticks) is causing a flush

        #!/usr/bin/perl
use strict;
use warnings;
use feature qw{ say };

unlink "./log.txt" or warn "$!";


open OUT, '>>', 'log.txt' or die $!;
print OUT "before system\n";

print `type log.txt`;

print OUT "after system\n";

open IN, '<', 'log.txt' or die $!;
my $nothing = <IN>;
say "Before close: $nothing.\n";


close OUT;
my $bla = <IN>;
say "After close: $bla.\n";

        [download]

        -*- mode: compilation; default-directory: "d:/tmp/pm/" -*-
Compilation started at Thu Feb 11 19:29:04

C:/Perl_524/bin\perl.exe -w d:/tmp/pm/auto_flush.pl 
before system
Before close: before system
.

After close: after system
.


Compilation finished at Thu Feb 11 19:29:05

        [download]

        Cheers Rolf
        (addicted to the Perl Programming Language :)
        Wikisyntax for the Monastery

[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom