perl,重定向stdout,但保持父级

在孩子身上,执行

open STDOUT, "|-", "tee", $output
  or die "$0: failed to start tee: $!";

如果你不想使用 tee 出于某种原因,你可以用叉子叉一个穷人的版本 另一个 儿童通道 open STDOUT, "|-" 在孙子身上做复制:

#! /usr/bin/perl

use warnings;
use strict;

my $pid = fork;
die "$0: fork: $!" unless defined $pid;

if ($pid) {
  waitpid $pid, 0;
}
else {
  my $pid = open STDOUT, "|-";
  die "$0: fork: $!" unless defined $pid;
  select STDOUT; $| = 1;  # disable STDOUT buffering
  if ($pid) {
    print "Hiya!\n";
    system "echo Howdy";
    close STDOUT or warn "$0: close: $!";
    exit 0;
  }
  else {
    open my $fh, ">", "/tmp/other-output" or die "$0: open: $!";
    my $status;
    while ($status = sysread STDIN, my $data, 8192) {
      syswrite $fh, $data and print $data or die "$0: output failed: $!";
    }
    die "$0: sysread: $!" unless defined $status;
    close $fh or warn "$0: close: $!";
    exit 0;
  }
}

样品运行:

$ ./owntee 
Hiya!
Howdy

$ cat other-output 
Hiya!
Howdy

如果父级可以等待子级完成,则子级可以将其输出返回父级,父级负责将其打印到stdout和目标文件:

open my $destfile, '>', $path or die "Can't open destination file: $!\n";

my $pid = open my $child, '-|';
defined $pid or die "Can't fork: $!\n";

if ($pid == 0) {
    # Child process:
    print "I'm the child!\n";
    close $destfile;
    #  do whatever
    exit;
}

# Parent process:

while (<$child>) {
    print STDOUT    $_;
    print $destfile $_;
}

close $child;
close $destfile;

事实上,即使家长不能等待孩子完成任务,如果家长首先将一个子分叉来执行上面概述的逻辑,这个策略仍然有效。