Perl无法写入子进程中的文件句柄

Question

我需要将一些数据写入child中的文件句柄.文件句柄是在分叉之前在父级中创建的.这是因为我可以从父文件句柄中读取数据,因为fork保留文件句柄并锁定它们(如果有的话),在父和子之间共享.这是在Linux和Windows平台上共享父和子的数据.我能够在Linux中使用IPC :: Shareable进行数据共享,这在windows中不起作用,因为windows中没有semaphore.pm [windos不支持semaphore.pm],所以对于windows我试过Win32 :: MMF哪个崩溃了我的perl编译器.

因此,使用文件句柄方法,IO写入不会发生在子级中.请查看以下代码

---

use strict;
use warnings;

print "creating file\n"; 
open FH, ">testfile.txt" or die "cant open file: $!\n";
close FH;

my $pid = fork();

if ( $pid == 0 )
{
print "entering in to child and opening file for write\n";
open FH, ">>testfile.txt" or die "cant open file: $!\n";
print FH "dummy data\n";
print FH "dummy data\n";     
print "child sleeping for 5 sec before exiting\n";
sleep 50;
exit;

}
else
{
print "entering the parent process\n";   
open FH, "<testfile.txt" or die "cant open file: $!\n";
 print <FH>;
 print <FH>;


}

---

Answer 1

父进程应至少等待几分之一秒，以便给子进程一些时间进行写入。

use strict;
use warnings;

print "creating file\n";
open my $FH, ">", "testfile.txt" or die "cant open file: $!\n";
close $FH;

my $pid = fork();

if ( $pid == 0 ) {
  print "entering in to child and opening file for write\n";
  open my $FH, ">>", "testfile.txt" or die "cant open file: $!\n";
  print $FH "dummy data\n";
  print $FH "dummy data\n";

  # print "child sleeping for 5 sec before exiting\n";
  # sleep 50;
  exit;
}
else {
  sleep 1;
  print "entering the parent process\n";
  open my $FH, "<", "testfile.txt" or die "cant open file: $!\n";
  print while <$FH>;
}

输出

creating file
entering in to child and opening file for write
entering the parent process
dummy data
dummy data