http://qs321.pair.com?node_id=11128250


in reply to Re^3: 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

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]

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Re^5: Why can't I write to a custom log from a Catalyst application on SELinux/CentOS
by LanX (Saint) on Feb 11, 2021 at 18:37 UTC
    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]
      even easier is using method autoflush directly.

      Got it from HaukeX' recent post.

      I should have read the FAQ: https://perldoc.perl.org/perlfaq5#How-do-I-flush/unbuffer-an-output-filehandle?-Why-must-I-do-this? more carefully :) 

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

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



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



if (0){                                 # as you like
    my $previous_default = select(OUT); # save previous default
    $|++;                               # autoflush OUT
    select($previous_default);          # restore previous default
} else {
    #use PerlIO;                         # needed for Perl <5.14
    OUT->autoflush();
}


print OUT "before close";

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

my $read;

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

close OUT;

      [download]

      -*- mode: compilation; default-directory: "d:/tmp/pm/" -*-
Compilation started at Fri Feb 12 02:23:56

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

Compilation finished at Fri Feb 12 02:23:56

      [download]

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

[reply]
[d/l]
[select]
Re^5: Why can't I write to a custom log from a Catalyst application on SELinux/CentOS
by LanX (Saint) on Feb 11, 2021 at 18:30 UTC
    > 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]

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