use feature qw(say);
use strict;
use warnings;
use POSIX ();
my @data = (q(child.pl 'dummy'),q(child.pl),q(bash -c child.pl),q(sh -c child.pl));
for ( @data ) {
say "Running command '$_'..";
my $res = system $_;
my $signal = $res & 127;
my $rval = $res >> 8;
say "Parent received return value: $rval";
if ( $signal == POSIX::SIGINT ) {
say "Parent received SIGINT";
}
}
和child.pl：
use feature qw(say);
use strict;
use warnings;
eval {
local $SIG{INT} = sub { die "Aborted by user.\n" };
sleep 10;
};
if ( $@ ) {
print "\n" . $@;
exit 0;
}
say "Timed out..";
exit 1;
如果我在超时前按CTRL-C,输出如下：
Running command 'child.pl 'dummy''.. ^C Aborted by user. Parent received return value: 0 Parent received SIGINT Running command 'child.pl'.. ^C Aborted by user. Parent received return value: 0 Running command 'bash -c child.pl'.. ^C Aborted by user. Parent received return value: 0 Running command 'sh -c child.pl'.. ^C Aborted by user. Parent received return value: 0 Parent received SIGINT
因此,在第一种情况和最后一种情况下,父节点接收SIGINT,而对于第二种和第三种情况,它不接收SIGINT.
这是什么原因？如何修复以使SIGINT不会传播给第一个和最后一个案例？
(我怀疑它与Shell的类型有关,即sh vs bash)
解决方法
system($shell_command)
是的缩写
system({ "/bin/sh" } "/bin/sh","-c",$shell_command)
除非shell命令不包含shell元字符,但在这种情况下不包含空格
system($shell_command)
是的缩写
my @cmd = split(' ',$shell_command);
system({ $cmd[0] } @cmd)
因此,
system("child.pl 'dummy'") is short for system({ "/bin/sh" } "/bin/sh","child.pl 'dummy'")
system("child.pl") is short for system({ "child.pl" } "child.pl")
system("bash -c child.pl") is short for system({ "bash" } "bash","child.pl")
system("sh -c child.pl") is short for system({ "sh" } "sh","child.pl")
值得注意的是,bash将自己替换为child.pl,而不是在此特定情况下在单独的进程中生成它.这使得child.pl在第三种情况下成为parent.pl的直接子项(就像第二种情况一样).
其次,让我们知道Ctrl-C的作用.
按下Ctrl-C时,终端将SIGINT发送到以该终端为控制终端的每个进程.换句话说,SIGINT被发送到会话的每个进程.
通过添加系统可以看到(“ps -o pid,ppid,pgrp,sid,cmd”);到child.pl,我们的会话中有三到四个进程,具体取决于测试用例.
> child.pl：child.pl处理SIGINT.它没有被它杀死.
> shell在测试用例1和4中由parent.pl启动：shell被SIGINT杀死.
> parent.pl：系统相当于本地$SIG {INT} =’IGNORE’;,因此忽略了SIGINT.
>启动parent.pl的登录shell：它忽略了SIGINT,但我不知道为什么.我猜它是因为它是一个交互式shell.
所以,这就是你所观察到的：
>当parent.pl的(直接)子节点是child.pl [测试用例2和3]时,子节点(child.pl)不会死于SIGINT,因为它处理SIGINT.>当parent.pl的(直接)子节点是shell [测试用例1和4]时,子节点(shell)从SIGINT消失,因为非交互式shell不处理/忽略SIGINT.