linux-bash信号陷阱将覆盖其nohup子命令的信号？

今天,我遇到了一个问题,由Shell脚本启动的程序无法接收INT信号.经过一番调查,我将在下面显示我的发现.

这是我要运行的目标程序,我使用gcc hello.c -o hello.out进行编译.如果您手动启动该程序,则可以通过kill -2来停止它.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>


int main()
{
    while (1) {
        printf("--------Hello Wolrd!\n");
        sleep(2);
    }
    return 0;
}

然后,我有一个Shell脚本,该脚本在启动程序之前会进行一些处理.这是简洁的版本,我们将其称为trap.sh：

#!/bin/bash

pid=0

function singal_handler() {
    echo "pid is "$java_pid
}

trap "singal_handler" INT

pid=2

nohup ./hello.out &

while true; do
    echo "running...."
    sleep 2
done

注意,我使用trap捕获INT信号来完成自己的工作,并使用nohup启动hello.out.

现在,我通过bash trap.sh启动程序.

通过向我的trap.sh发出kill -2,可以预期该行为,即pid输出消失了.

令我惊讶的是,这时,当我向后台发出kill -2 hello.out时,hello.out仍然存在,但不会消失.

所以我写这个问题来问为什么会发生这种情况. bash陷阱会覆盖其子命令的信号处理程序吗？

我的平台是64位linux：

uname -r —–> 3.10.0-123.el7.x86_64

谢谢.

解决方法:

bash manual说：

When a simple command other than a builtin or shell function is to be executed, it is invoked in a separate execution environment that consists of the following. Unless otherwise noted, the values are inherited from the shell.

• the shell’s open files, plus any modifications and additions specified by redirections to the command
• the current working directory
• the file creation mode mask
• shell variables and functions marked for export, along with variables exported for the command, passed in the environment (see Environment)
• traps caught by the shell are reset to the values inherited from the shell’s parent, and traps ignored by the shell are ignored

man sigaction说：

A child created via fork(2) inherits a copy of its parent’s signal dispositions. During an execve(2), the dispositions of handled signals are reset to the
default; the dispositions of ignored signals are left unchanged.

所以是的,SIGINT get被忽略了,因为父外壳将忽略它.