Perl fork(),exec()然后kill创建僵尸进程

Question

我试图使用fork,exec在perl中启动android模拟器.之后我也需要杀掉它但杀死它会导致僵尸进程与后台运行的模拟器.

我尝试过使用kill -1以及kill -9和killall -v emulator.我也通过附加显式exec("exec命令...")尝试了exec'ing,但无论哪种方式,我都会得到一个僵尸进程,直到perl脚本运行.

这是我的代码:

my $CMD;
my $PID;

sub waitkey()
{
    local( $| ) = ( 1 );
    print "Press <Enter> or <Return> to continue: ";
    my $resp = <STDIN>;
}


$|++;

$CMD = "emulator -avd audit -no-snapshot-save";
# $CMD = "exec emulator -avd audit -no-snapshot-save";

$PID = fork();
if ($PID==0) 
{
    print "forked!\n\n";
    sleep(1);
    exec("$CMD");
    die "Unable to execute";
}

print "PID: $PID\n\n";

sleep(1);
print "------ Processes before killing -----\n";
print `ps aux | grep emulator`;
print "------ Press a key to kill -----\n\n"

&waitkey;
# `kill -1 $PID`;
`kill -9 $PID`;

print "------ Processes after killing -----\n";
sleep(1);
print `ps aux | grep emulator`;


print "----- waiting ... -----\n";
#-- do somehing here with assumption that emulator has been killed --
&waitkey;

在输出中我看到了

------ Processes before killing -----
qureshi  10561  0.0  0.0   3556   980 pts/5    S+   13:28   0:00 emulator -avd audit -no-snapshot-save
qureshi  10562  0.0  0.0   4396   616 pts/5    S+   13:28   0:00 sh -c ps aux | grep emulator
qureshi  10564  0.0  0.0  13580   928 pts/5    S+   13:28   0:00 grep emulator

并且在杀死过程之后

------ Processes after killing -----
qureshi  10561 30.0  0.0      0     0 pts/5    R+   13:28   0:01 [emulator64-arm]
qureshi  10619  0.0  0.0   4396   612 pts/5    S+   13:28   0:00 sh -c ps aux | grep emulator
qureshi  10621  0.0  0.0  13580   932 pts/5    S+   13:28   0:00 grep emulator

我如何摆脱僵尸进程？

Answer 1

僵尸只是一个进程表条目,它等待父进程来到并收集其退出状态.如perldoc前叉所述,

如果你在没有等待孩子的情况下分叉,你就会积累僵尸.在某些系统上,您可以通过将$ SIG {CHLD}设置为"IGNORE"来避免这种情况.

设置$SIG{CHLD}适用于大多数unix类型的系统,包括Linux,因此这是安排孩子安息的最简单方法.

BTW,使用&前缀调用用户定义的函数是Perl 4-ism.在当前的Perl版本中,您应该使用just waitkey或waitkey()代替&waitkey.