Perl 为什么在生成守护进程时utf8 IO层会被剥离?
以下代码按预期工作:Perl 为什么在生成守护进程时utf8 IO层会被剥离?,perl,encoding,utf-8,Perl,Encoding,Utf 8,以下代码按预期工作: use feature qw(say); use strict; use warnings; use open qw/:std IN :encoding(utf-8) OUT :utf8/; say join ' ', (PerlIO::get_layers(\*STDOUT)); my $pid = fork(); die "fork() failed: $!" unless defined $pid; if ($pid == 0) { say join
use feature qw(say);
use strict;
use warnings;
use open qw/:std IN :encoding(utf-8) OUT :utf8/;
say join ' ', (PerlIO::get_layers(\*STDOUT));
my $pid = fork();
die "fork() failed: $!" unless defined $pid;
if ($pid == 0) {
say join ' ', (PerlIO::get_layers(\*STDOUT));
}
输出:
unix perlio utf8
unix perlio utf8
但如果我使用守护进程而不是常规fork:
use feature qw(say);
use strict;
use warnings;
use open qw/:std IN :encoding(utf-8) OUT :utf8/;
use Cwd qw(getcwd);
use Proc::Daemon;
my $work_dir = getcwd;
my $daemon = Proc::Daemon->new(
work_dir => $work_dir,
child_STDOUT => 'stdout.txt',
child_STDERR => 'stderr.txt',
pid_file => 'pid.txt',
);
my $pid = $daemon->Init();
if ( $pid == 0 ) {
say join ' ', (PerlIO::get_layers(\*STDOUT));
}
文件stdout.txt
的输出为:
unix perlio
因此,utf8
IO层已被剥离。考虑以下示例:
下午六时
package Foo;
use warnings;
use strict;
sub test {
close STDIN;
open \*STDIN, "<", "/dev/null";
}
1;
看起来
使用open
与其他杂注类似,只适用于其中的文件。因此,当Proc::Daemon
关闭标准输入、输出和错误并重新打开它们时,它自然看不到额外的层。如中所述,该模块关闭stdin等并重新打开它们。我不确定,但我打赌open
pragma在词汇范围上与大多数其他语言一样;在一个包中设置它不会改变其他包的工作方式。use open
是词汇范围。(除了:std
部分,它会导致立即调用binmode
)
#!/usr/bin/perl
use strict;
use warnings;
use feature qw/say/;
use open qw/:std IN :encoding(UTF-8) OUT :encoding(UTF-8)/;
use lib qw/./;
use Foo;
$, = ' ';
say "Original STDIN:", PerlIO::get_layers(\*STDIN);
close STDIN;
open \*STDIN, "<", "/dev/null";
say "Reopened STDIN:", PerlIO::get_layers(\*STDIN);
Foo::test();
say "Reopened STDIN in different package:", PerlIO::get_layers(\*STDIN);
$ perl test.pl
Original STDIN: unix perlio encoding(utf-8-strict) utf8
Reopened STDIN: unix perlio encoding(utf-8-strict) utf8
Reopened STDIN in different package: unix perlio