在后台 shell 脚本中使用 netcat/cat(如何避免停止(tty 输入)?) [英] Using netcat/cat in a background shell script (How to avoid Stopped (tty input)? )

问题描述

摘要:如何在后台运行交互式任务?

Abstract: How to run an interactive task in background?

详细信息:我正在尝试在 ash shell (Busybox) 下运行这个简单的脚本作为后台任务.

Details: I am trying to run this simple script under ash shell (Busybox) as a background task.

myscript.sh&

myscript.sh&

但是脚本会立即停止...

However the script stops immediately...

[1]+ 已停止(tty 输入)myscript.sh

[1]+ Stopped (tty input) myscript.sh

myscript.sh 内容...(仅相关部分，除此之外我捕获 SIGINT、SIGHUP 等)

The myscript.sh contents... (only the relvant part, other then that I trap SIGINT, SIGHUP etc)

#!/bin/sh

catpid=0

START_COPY()
{
  cat /dev/charfile > /path/outfile &
  catpid = $! 
}

STOP_COPY()
{
  kill catpid 
}

netcat SOME_IP PORT | while read EVENT
do
  case $EVENT in
    start) START_COPY;;
    stop) STOP_COPY;;
  esac
done

通过简单的命令行测试，我发现 bot cat 和 netcat 尝试从 tty 读取.请注意，此 netcat 版本没有 -e 来抑制 tty.

From simple command line tests I found that bot cat and netcat try to read from tty. Note that this netcat version does not have -e to supress tty.

现在可以做些什么来避免 myscript 停止?

Now what can be done to avoid myscript becoming stopped?

我尝试过的事情都没有成功:

Things I have tried so for without any success:

1) netcat/cat ...

/dev/tty(或 tty 的输出)

1) netcat/cat ... < /dev/tty (or the output of tty)

2) 使用 () 在子 shell 中运行包含 cat 和 netcat 的块.这可能有效，但是如何获取猫的 PID?

2) Running the block containing cat and netcat in a subshell using (). This may work but then how to grab PID of cat?

交给各位专家...

问题依然存在.一个简单的测试供大家尝试:

The problem still exists. A simple test for you all to try:

1) 在一个终端运行 netcat -l -p 11111 (不带 &)

1) In one terminal run netcat -l -p 11111 (without &)

2) 在另一个终端运行 netcat localhost 11111 &(这应该会在一段时间后停止并显示消息已停止(TTY 输入))

2) In another terminal run netcat localhost 11111 & (This should stop after a while with message Stopped (TTY input) )

如何避免这种情况?

推荐答案

你可能想要 netcat 的 "-d" 选项，它告诉它不要从 STDIN 读取.

you probably want netcat's "-d" option, which tells it not to read from STDIN.

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