1

我试图学习fork，这是一个简单的程序：

#!/usr/bin/perl
# PRGNAME.pl by Whom
#
#
use strict;
use warnings;

main(@ARGV);

sub main
{
    my @array = qw(1 2 3 4 5 6);
    while ( (my $t = pop @array) ) {
        if (! (my $pid = fork) ) {
                exit if ( $t == 2 );
                for(;;){}
        }
    }
    waitpid(-1, 0);
    message("This is the $PRGNAME exercise file.");
}

sub message
{
    my $m = shift or return;
    print("$m\n");
}

sub error
{
    my $e = shift || 'unkown error';
    print("$0: $e\n");
    exit 0;
}

但是当我尝试时在外壳上：ps -fu $LOGNAME | grep [f]ork，我发现：

  i59tib 28361     1   3 16:20:07 pts/34      6:07 /usr/bin/perl ./fork.pl
  i59tib 28363     1   3 16:20:07 pts/34      6:07 /usr/bin/perl ./fork.pl
  i59tib 28366     1   3 16:20:07 pts/34      6:07 /usr/bin/perl ./fork.pl
  i59tib 28364     1   3 16:20:07 pts/34      6:07 /usr/bin/perl ./fork.pl
  i59tib 28362     1   3 16:20:07 pts/34      6:08 /usr/bin/perl ./fork.pl

当我评论这一行时，其中一个进程及其父进程已退出exit if ( $t == 2 );

再次运行ps -fu $LOGNAME | grep [f]ork，我发现：

  i59tib   624   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   629   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   628   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   625   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   627   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   626   623   1 16:29:11 pts/34      0:04 /usr/bin/perl ./fork.pl
  i59tib   623  4766   0 16:29:11 pts/34      0:00 /usr/bin/perl ./fork.pl

如何在不退出父进程的情况下退出子进程？

4

2 回答 2

3

如何在不退出父进程的情况下退出子进程？

父级退出是因为父级到达程序的结尾，所以告诉父级做点什么，什么都行！例如，

1 while waitpid(-1, 0) > 0;
于 2013-10-14T15:23:28.197 回答
0

如何在不退出父进程的情况下退出子进程？

在这里尝试下面的程序孩子在父母之前死去。

#!/usr/bin/perl
print "i am about to fork\n";
my $pid = fork();
if($pid > 0) {
    my $i = 0;
    while($i<5) {
         print "PARENT--I will be keep on running\n";
         sleep(5);
         $i++;
    }
    print "PARENT-- I m about to dead\n";
} else {
    $i = 0;
    while($i <3) {
        print "CHILD-- I will be dead before than parent\n";
        #exit(0);   you can put exit like this also.
        sleep(2);
        $i++;
    }
    print "CHILD-- I m about to dead\n";
}

下面是示例输出。

i am about to fork
PARENT--I will be keep on running
CHILD-- I will be dead before than parent
CHILD-- I will be dead before than parent
CHILD-- I will be dead before than parent
PARENT--I will be keep on running
CHILD-- I m about to dead
PARENT--I will be keep on running
PARENT--I will be keep on running
PARENT--I will be keep on running
PARENT-- I m about to dead

您也可以使用任何支持的信号。您可以在此处获取不同的信号列表。您也可以在循环中使用相同的示例代码，但请确保这里有一个超级父母，另一个是他们的孩子。

请运行此程序以了解更多信息。无论您是否使用退出，超级父级总是会在最后退出。

#!/usr/bin/perl
print "i $$ am about to fork\n";
my @children_pids;
my $n = 3;
for my $i ( 0..($n-1) ) {
    my $pid = fork();
    if($pid > 0) {
        print "i m $$ child of".getppid()."\n";
        push @children_pids, $pid;
    } else {
        print "I $$ is about to dead. I am child of".getppid()."\n";
        exit();
    }
}
waitpid $_, 0 for @children_pids;
print "$$ is finished\n";

我的上述程序系统的典型输出如下。

i 3919 am about to fork
i m 3919 child of3092
I 3920 is about to dead. I am child of3919
i m 3919 child of3092
i m 3919 child of3092
I 3921 is about to dead. I am child of3919
I 3922 is about to dead. I am child of3919
3919 is finished

父级将等待其所有子级退出；然后只有它会退出。

于 2013-10-14T18:43:04.127 回答