nohup 和 & 和有什么不一样 [英] What's the difference between nohup and ampersand

问题描述

nohup myprocess.out & 或 myprocess.out & 都将 myprocess.out 设置为在后台运行.关闭终端后，该进程仍在运行.它们有什么区别?

Both nohup myprocess.out & or myprocess.out & set myprocess.out to run in the background. After I shutdown the terminal, the process is still running. What's the difference between them?

推荐答案

nohup 捕获挂断信号(参见 man 7 signal)，而 & 符号没有(除了外壳是这样配置的，或者根本不发送 SIGHUP).

nohup catches the hangup signal (see man 7 signal) while the ampersand doesn't (except the shell is confgured that way or doesn't send SIGHUP at all).

通常，当使用 & 运行命令并随后退出 shell 时，shell 将使用挂断信号终止子命令(kill -SIGHUP ).这可以使用 nohup 来防止，因为它会捕获信号并忽略它，因此它永远不会到达实际应用程序.

Normally, when running a command using & and exiting the shell afterwards, the shell will terminate the sub-command with the hangup signal (kill -SIGHUP <pid>). This can be prevented using nohup, as it catches the signal and ignores it so that it never reaches the actual application.

如果您使用的是 bash，您可以使用命令 shopt |grep hupon 查看是否您的 shell 是否向其子进程发送 SIGHUP.如果它关闭，进程将不会已终止，因为您的情况似乎如此.有关 bash 如何终止的更多信息可以在此处找到应用程序.

In case you're using bash, you can use the command shopt | grep hupon to find out whether your shell sends SIGHUP to its child processes or not. If it is off, processes won't be terminated, as it seems to be the case for you. More information on how bash terminates applications can be found here.

在某些情况下 nohup 不起作用，例如当您启动的进程重新连接时SIGHUP 信号，因为它是这种情况 此处.

There are cases where nohup does not work, for example when the process you start reconnects the SIGHUP signal, as it is the case here.

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